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#Post#: 82--------------------------------------------------
NCGT NO PLATE TECTONICS
By: Admin Date: January 29, 2017, 7:58 am
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NCGT 63
80 PROGRESS REPORT OF THE STUDY OF ANCIENT CONTINENTALROCKS IN
THE PACIFIC OCEAN
Boris I. VASILIEV*, Takao YANO** and Dong R. CHOI**** Pacific
Oceanological Institute, Far East Branch, Russian Academy of
Science, Vladivostok,690041, Russia. boris@poi.dvo.ru;
gavrilov@poi.dvo.ru** Department of Environment Science, Faculty
of Regional Science, Tottori Univ., Tottori, 680-855,Japan.
yanot@rstu.jp*** Raax Australia Pty Ltd., 6 Mann Place, Higgins,
ACT 2615, Australia. raax@ozemail.com.au
On the basis of deep-water drillings, dredgings and extensive
geological researches, Vasiliev (2009) described thedetailed
geology of the Pacific Ocean and discussed its origin. His book
is the latest and most comprehensivestudy in the history of
geological research on the Pacific Ocean. Choi and Pavlenkova
(2009) and its citing fourpapers by authors including Choi D.R.
clarified the overall geologic and geophysical characteristics
of the PacificOcean and investigated its tectonic development
from the viewpoint of global block tectonics. Yano et al.
(2009,2011) reviewed the occurrence of ancient continental rocks
in the Atlantic and Indian Oceans.We are now focusing on ancient
continental rocks found in the Pacific Ocean as a key to
elucidating its geologiccharacter. So far, such rocks have been
found at 98 localities in that ocean (Fig. 1). Over half occur
in thesouthwestern Pacific Ocean, concentrated in Zealandia
(Luyendyk, 1995), a mainly submerged continental block,one third
the size of Australia. The rest are found all over the ocean,
including deep ocean basins, the East PacificRise and
continent-ocean transitions.Together with 42 localities in the
Atlantic Ocean (Yano et al., 2009) and 32 in the Indian Ocean
(Yano et al.,2011), ancient continental rocks have been found at
172 localities in the world oceans. Among them, Type Arocks
(continental rocks located in continent-ocean transitions deeper
than the ocean-floor depth) from 87localities prove that part of
the continent has subsided and become ocean floor. Type B and C
rocks (continentalrocks and rocks with continental geochemical
signatures, located in mid-oceanic ridges and ocean basins)
from78 localities point to the original continental nature of
the oceans. Type D rocks (ancient rocks and fossilssignificantly
older than predicted oceanic plate ages) from 7 localities
indicate that oceanic lithosphere dates,respectively, back to
1.9 Ga and the Ordovician [this means that radiometric ages of
oceanic lithospheric rocksdate back to 1.9 Ga and ancient
fossils obtained from oceanic floor back to the
Ordovician].There are certainly many more data not yet obtained
or so far unobtainable, so we would like to continue ourreview
and at some point create an open-access public database to which
others can contribute. Since marinegeological surveys are still
extremely sparse and the ancient continental rocks discovered to
date have been foundmostly by accident, future drilling and
dredging may prove the systematic presence of ancient
continental rocks inthe world oceans. Exploring by IODP,
particularly through deep drillings by "Chikyu" is expected to
clarify thenature of oceanic crust. All hypotheses on the origin
of the oceans should be reexamined in the light of theincreasing
volume of such rock specimens from the ocean floor.The ancient
and continental rocks that have endured severe tectono-magmatic
destruction during the Meso-Cenozoic are clearly telling us that
the geology of the oceans is not entirely different from that of
the continentsand that the oceans have prolonged continental
prehistories. They provide invaluable evidence in our efforts
tolearn the truth about the Earth.References citedChoi, D.R. and
Pavlenkova N.I., 2009. Geology and tectonic development of the
Pacific Ocean. Part 5. Global lowgravitybelt: an outer ring of
the great Pacific ring structure. NCGT Newsletter, no. 50, p.
46-54. www.ncgt.org.Luyendyk, B.P. 1995. Hypothesis for
Cretaceous rifting of east Gondwana caused by subducted slab
capture. Geology,v. 23, p. 373-376.Smith, W.H.F. and Sandwell,
D.T., 1997. Global seafloor topography from satellite altimetry
and ship depth soundings.Science, v. 277, p. 1957-1962.
<
HTML http://topex.ucsd.edu/WWW_html/mar_topo.html>Vasiliev,
B.I.,
2009. Geological Structure and Origin of the Pacific Ocean.
560p., Dalnauka, Vladivostok. [in Russianwith English
contents]New Concepts in Global Tectonics Newsletter, no. 63,
2012. www.ncgt.org81Yano T., Choi D.R., Gavrilov A.A., Miyagi,
S. and Vasiliev B.I., 2009. Ancient and continental rocks in the
AtlanticOcean. NCGT Newsletter, no. 53, p. 3-17.
www.ncgt.org.Yano T., Vasiliev B.I., Choi D.R., Miyagi, S.,
Gavrilov A.A. and Adachi, H., 2011. Continental rocks in the
IndianOcean. NCGT Newsletter, no. 58, p. 9-28. www.ncgt.org.Fig.
1. Distribution of ancient and continental rocks in the Pacific
Ocean. Topography after Smith and Sandwell(1997).New Concepts in
Global Tectonics Newsletter, no. 63, 2012. www.ncgt.org
-----
New Concepts in Global Tectonics NEWSLETTER www.ncgt.org
No. 63, June, 2012
MEA CULPA: THE EARTH IS NOT EXPANDING – BUT THE
CONTINENTS ARE NOT MOVING EITHER.
Stephen FOSTER
hero5.premiere@blueyonder.co.uk
... 85
Discussion
There is a great deal of other data ... (for many other
references see sources cited and numerous articles and
references therein in NCGT Newsletter which is freely
available).
It is abundantly clear from rocks drilled from all of the
world's ocean floors that the ocean basins are young - Mesozoic
and Cenozoic - and that there was a period of rapid subsidence
from the mid-Miocene to present. The bulk of the water in the
world's oceans was expelled from the mantle at the time the
basins were subsiding and these processes are linked (Rezanov,
2003). ... In 2010 ... I was unaware of the ways in which much
data from the ocean floors is and has been presented in a biased
and distorted fashion*1 and argued for an expanding earth as I
believed seafloor spreading to be true. Mea culpa: I was wrong.
Seafloor spreading, like subduction and earth expansion is a
myth which has no place in science. The continents are not
moving laterally, nor have they done so at any time in the past.
The modern oceans started to form in the Jurassic and
Cretaceous, including much of the Pacific, the south and central
Atlantic and the southern Indian Oceans (Rezanov, 2003). In the
late Cretaceous to Palaeogene the rest of the ocean basins were
submerged but they did not subside to their current depths until
the late Miocene to Pliocene. The ocean trenches subsided from
the late Miocene to present: all of these conclusions are based
on sediment and fossils recovered from cores not geophysical
data. The bulk of the water in the world's oceans was expelled
from the mantle at the same time that the basins were subsiding:
both processes were linked. Rezanov offers a theory to explain
both the rapid subsidence and the accompanying release of large
volumes of water from the mantle which now forms the oceans.
-----
NORTHEASTERN PACIFIC AND THE CASCADIA MARGIN:
SNAKE-OIL TECTONICS
N. Christian SMOOT
Christiansmoot532@gmail.com
The fact remains that the ages of both the magnetic isochrons
and of the corresponding ocean floor are definitely suspect, as
they have not been ground-truthed. Based on the ages listed, and
the ages listed of the seamounts in the Gulf of Alaska, one can
easily understand why such a problem exists with the hotspot
hypothesis.The plate tectonics proponents need a source of new
seafloor in the NE Pacific. Otherwise, ocean floor spreading in
this ocean basin ceases north of the East Pacific Rise. This
ridge assortment seemed to be the perfect choice. However, in
order to accommodate eastward spreading up against continental
crust, they had to create a subduction zone to clean the floor
of the Endeavor, Juan de Fuca, and Gorda plate material. After
all, new crust is being produced at an average 6.5 cm/yr
according to their figures. Clearly this is not the case. The
Cascadia Subduction Zone/Fault does not exist. This in itself is
interesting, because the San Andreas and Queen Charlotte faults
on either end are extremely active with both horizontal and
vertical movement. In the favor of the hypothesis, Mt. St.
Helens is continuously rumbling. Mount Lassen is occasionally
active, as are others in the Cascade Range such as Hood and
Rainier. None of this appears in the earthquake events data
base. Actually, using the available data, one can state that the
tectonic scenario for the Northeastern Pacific Basin might be in
the lineations and seamount ages. The seamount lineations and
ages are generally northwest to southeast. The heavily
sedimented Alaskan and Tufts Abyssal Plains are hard to make any
sense out of, but the lineation directions provide a good clue.
The fact that the three all stop a goodly distance from the
spreading centers leaves another good clue (Figure 4). Obviously
all three “hotspots” did not cease activity at the same time, so
that seamount formation from the east at a hotspot that was
located on “0” age crust is not a viable solution to the problem
at all. Rather, the seamounts seem to have formed on
pre-existing crust from a source beneath and to the west of the
present seamount locations. This would be in heated channels
whose source is undetermined at the present and whose driving
force is Earth's rotation. The channels seem to be located
beneath fracture zones. As serendipity would have it, three
fracture zones exist in the Gulf of Alaska, all of which are
known to exist but have not been definitely located with the
exception of the positions in the US Board on Geographic Names
(1990): Aja at 56o N, Sila at 51o N, and Sedna at 47o30' N. None
are perpendicular to the spreading ridges on the east, and Aja
and Sila lie directly in the path of the two northern seamount
chains. As a final thought, we would all be remiss if we
continued to ignore one other trend, that of the seamount chain
passing northerly from Hook Ridge through Miller Seamount and
ending with Pratt Seamount. The line of smaller seamounts runs
from 50o N to 56o N latitude along about 142o W longitude. No
explanation is provided herein because this is so far removed
from any hypotheses I have ever seen that I would not even
hazard a guess. It does exist, though. and awaits the
explanation from someone far more qualified than I.
#Post#: 174--------------------------------------------------
REQUIREMENTS OF PLATE TECTONICS
By: Admin Date: March 16, 2017, 8:45 pm
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204 New Concepts in Global Tectonics Journal, V. 4, No. 2, June
2016. www.ncgt.org
Critical analysis of the plate tectonics model and causes of
horizontal tectonic movements
Arkady Pilchin
Universal Geosciences & Environmental Consulting Company
205 Hilda Ave., #1402
Toronto, Ontario, M2M 4B1, Canada.
arkadypilchin@yahoo.ca
- Abstract: The main problems of the plate tectonics model are
discussed in the paper. It is shown that the idea of mantle-wide
convection, as well as convection within any thick mantle layer,
violates the laws of physics and is therefore impossible.
Analysis of the forces postulated for the model reveals that
their values are very low and would be incapable of forming and
supporting any significant tectonic processes (e.g., obduction,
orogeny, uplifting of lithospheric block, subduction, and
others). There is no clear definition of the forces operating in
plate tectonics and movement of plates; and even their
application is incorrect, as they violate physical laws by
ignoring friction and strength limits. Formation of a new
oceanic lithosphere in spreading centers violates physical laws,
because it is not possible to have a plate which would
independently form all its main layers of the oceanic
lithosphere over tens to hundreds of millions of years in
underwater conditions, building up in ~1 cm long, 50 km thick
and thousands of kilometers wide increments each year, all to
combine into a thousands of kilometers long solid oceanic plate,
separated into its layers. There are inconsistencies between the
total lengths of mid-ocean ridges (total length of the mid-ocean
ridge system is ~80,000 km and the continuous mountain range is
65,000 km) and the total length of trenches (30,000-40,000 km)
on the sea floor, but according to the plate tectonics model the
total length of trenches should be twice as long as that of
mid-ocean ridges (~130,000-160,000 km). There is also data
indicating the impossibility for subduction to take place around
the Atlantic (except a few locations) and Arctic oceans. Any
oceanic lithosphere plate (slab) with a thickness of ~50 km is
composed of three main layers: brittle upper layer with a
temperature less than ~573 K; elastic middle layer with
temperatures within the range of ~573-873 K; and plastic lower
layer with a temperature of over ~873 K, and cannot be
considered rigid. Analysis of possible density of subducting
slabs shows that under any circumstances the average density of
an oceanic lithosphere plate cannot be greater than rocks of the
upper mantle, and formation of negative buoyancy should
therefore not be possible; even transformation of the entire
crust of any region into eclogite would be insufficient to form
a negative buoyancy of even 0.01 g/cm3. It is shown that the
subduction process requires presence of gigantic external force.
An oceanic plate has an average geothermal gradient of ~50-86
K/km, and a temperature of about 1573 K (or 1603 K) at the point
of contact between its lithosphere and asthenosphere, so it
cannot technically be considered cold. There are also numerous
questions in the model unanswered thus far. Formation of UHP
rocks cannot be accomplished within a subduction zone under
lithostatic pressures alone. Analysis of causes for the
formation of significant overpressure shows that only the
decomposition of rocks (foremost the serpentinization of
peridotite) can generate such giant forces capable of
horizontally moving oceanic plates. It is clear that the plate
tectonics model is inconsistent as a model, violates numerous
physical laws, and is based on a large number of false
postulates and assumptions.
Table 1. Some key postulates, assumptions, and requirements of
the plate tectonics model. Postulate; Assumption or Requirement;
Reference
_The Earth's surface consists of number of rigid plates (e.g.,
12 plates): Morgan, 1968
_Plates move relative to each other with a speed of ~1–10 cm
yr−1: Richter, 1973a
_Rigidity of lithospheric plates is one of the fundamental
tenets of plate tectonics: Solomon et al., 1975; Anderson, 2007a
_Mantle convection with large convection cells is the main cause
of plate motion*: Chapple and Tullis, 1977; Anderson, 1989
_Mantle convection is the driver of the Earth’s tectonic system:
Holmes, 1931, 1944
_Thermal convection in some form is the only source of
sufficient energy: McKenzie, 1969
_The energy for convection is provided by the decay of
radioactive isotopes of uranium, thorium and potassium, as well
as the cooling and crystallization of Earth: Anderson, 1989
_Sea floor spreading is related to mid-ocean ridges and the
formation of oceanic crust and upper mantle in them: Hess 1962;
Dietz 1961
_Formation of new oceanic crust/lithosphere within mid-ocean
ridges requires the consumption of the lithosphere in subduction
zones (e.g., within trenches and island arcs): McKenzie, 1969
_Subduction commonly involves convergence and underthrusting of
adjacent lithospheric plates, but may involve downfolding within
a single plate: White et al., 1970
_A peak subduction rate is about 5 cm per year: Mahatsente and
Ranalli, 2004
Slabs sink into the mantle because they are cold and dense:
Anderson, 2007a
_The cooler subducting lithosphere is heavier than the
underlying mantle, and it drags the attached plate: Elsasser,
1967; Cruciani et al., 2005
_Plate tectonics is driven by negative buoyancy of the outer
shell: Richardson, 1992; Anderson, 2001
_To start the subduction process, an oceanic plate must be
negatively buoyant: McKenzie, 1969; Elsasser, 1969
_To generate negative buoyancy, the subducting plate must
contain significant amount of eclogite: Anderson, 2007a
_Initiation of plate movement is directed by the plate boundary
and plate body forces, of which the main ones are: basal drag,
ridge push, slab pull, trench suction, and collisional
resistance: Richardson, 1992
_Plate tectonics is a far-from-equilibrium self-organized
system: Anderson, 2001, 2002a, 2007a; Stern, 2007
_Self-sustaining subduction occurs when the negative buoyancy
within a subduction zone is sufficiently large: Gurnis et al.,
2004
* - in a number of cases some postulates, assumptions and
requirements represent amalgamations of postulates, assumptions
and requirements (e.g., about convection, sea floor spreading,
subduction, negative buoyancy
#Post#: 175--------------------------------------------------
PRATT/ NO PLATE TECTONICS
By: Admin Date: March 16, 2017, 8:50 pm
---------------------------------------------------------
« Reply #5 on: March 05, 2017, 10:03:11 pm »
Plate Tectonics: A Paradigm Under Threat
David Pratt © 2000
HTML http://www.newgeology.us/presentation20.html
(First published in the Journal of Scientific Exploration, vol.
14, no. 3, pp. 307-352, 2000)
Abstract.
_-- This paper looks at the challenges confronting plate
tectonics -- the ruling paradigm in the earth sciences.
_The classical model of thin lithospheric plates moving over a
global asthenosphere is shown to be implausible.
_Evidence is presented that appears to contradict continental
drift, seafloor spreading and subduction, and the claim that the
oceanic crust is relatively young.
_The problems posed by vertical tectonic movements are reviewed,
including evidence for large areas of submerged continental
crust in today's oceans.
_It is concluded that the fundamental tenets of plate tectonics
might be wrong.
Introduction
_The idea of large-scale continental drift has been around for
some 200 years, but the first detailed theory was proposed by
Alfred Wegener in 1912.
_It met with widespread rejection, largely because the mechanism
he suggested was inadequate -- the continents supposedly plowed
slowly through the denser oceanic crust under the influence of
gravitational and rotational forces.
_Interest was revived in the early 1950s with the rise of the
new science of paleomagnetism, which seemed to provide strong
support for continental drift.
_In the early 1960s new data from ocean exploration led to the
idea of seafloor spreading.
_A few years later, these and other concepts were synthesized
into the model of plate tectonics, which was originally called
"the new global tectonics."
_According to the orthodox model of plate tectonics, the earth's
outer shell, or lithosphere, is divided into a number of large,
rigid plates that move over a soft layer of the mantle known as
the asthenosphere, and interact at their boundaries, where they
converge, diverge, or slide past one another.
_Such interactions are believed to be responsible for most of
the seismic and volcanic activity of the earth.
_Plates cause mountains to rise where they push together, and
continents to fracture and oceans to form where they rift apart.
_The continents, sitting passively on the backs of the plates,
drift with them, at the rate of a few centimeters a year.
_At the end of the Permian, some 250 million years ago, all the
present continents are said to have been gathered together in a
single supercontinent, Pangaea, consisting of two major
landmasses: Laurasia in the north, and Gondwanaland in the
south.
_Pangaea is widely believed to have started fragmenting in the
early Jurassic -- though this is sometimes said to have begun
earlier, in the Triassic, or even as late as the Cretaceous --
resulting in the configuration of oceans and continents observed
today.
_It has been said that "A hypothesis that is appealing for its
unity or simplicity acts as a filter, accepting reinforcement
with ease but tending to reject evidence that does not seem to
fit" (Grad, 1971, p. 636). Meyerhoff and Meyerhoff (1974b, p.
411) argued that this is "an admirable description of what has
happened in the field of earth dynamics, where one hypothesis --
the new global tectonics -- has been permitted to override and
overrule all other hypotheses."
_ Nitecki et al. (1978) reported that in 1961 only 27% of
western geologists accepted plate tectonics, but that during the
mid-1960s a "chain reaction" took place and by 1977 it was
embraced by as many as 87%.
_Some proponents of plate tectonics have admitted that a
bandwagon atmosphere developed, and that data that did not fit
into the model were not given sufficient consideration (e.g.
Wyllie, 1976), resulting in "a somewhat disturbing dogmatism"
(Dott and Batten, 1981, p. 151).
_McGeary and Plummer (1998, p. 97) acknowledge that "Geologists,
like other people, are susceptible to fads."
_Maxwell (1974) stated that many earth-science papers were
concerned with demonstrating that some particular feature or
process may be explained by plate tectonics, but that such
papers were of limited value in any unbiased assessment of the
scientific validity of the hypothesis.
_Van Andel (1984) conceded that plate tectonics had serious
flaws, and that the need for a growing number of ad hoc
modifications cast doubt on its claim to be the ultimate
unifying global theory.
_Lowman (1992a) argued that geology has largely become "a bland
mixture of descriptive research and interpretive papers in which
the interpretation is a facile cookbook application of
plate-tectonics concepts ... used as confidently as
trigonometric functions" (p. 3).
_Lyttleton and Bondi (1992) held that the difficulties facing
plate tectonics and the lack of study of alternative
explanations for seemingly supportive evidence reduced the
plausibility of the theory.
_Saull (1986) pointed out that no global tectonic model should
ever be considered definitive, since geological and geophysical
observations are nearly always open to alternative explanations.
_He also stated that even if plate tectonics were false, it
would be difficult to refute and replace, for the following
reasons: the processes supposed to be responsible for plate
dynamics are rooted in regions of the earth so poorly known that
it is hard to prove or disprove any particular model of them;
the hard core of belief in plate tectonics is protected from
direct assault by auxiliary hypotheses that are still being
generated; and the plate model is so widely believed to be
correct that it is difficult to get alternative interpretations
published in the scientific literature.
_When plate tectonics was first elaborated in the 1960s, less
than 0.0001% of the deep ocean had been explored and less than
20% of the land area had been mapped in meaningful detail.
_Even by the mid-1990s, only about 3 to 5% of the deep ocean
basins had been explored in any kind of detail, and not much
more than 25 to 30% of the land area could be said to be truly
known (Meyerhoff et al., 1996a).
_Scientific understanding of the earth's surface features is
clearly still in its infancy, to say nothing of the earth's
interior.
_Beloussov (1980, 1990) held that plate tectonics was a
premature generalization of still very inadequate data on the
structure of the ocean floor, and had proven to be far removed
from geological reality.
_He wrote: It is ... quite understandable that attempts to
employ this conception to explain concrete structural situations
in a local rather than a global scale lead to increasingly
complicated schemes in which it is suggested that local axes of
spreading develop here and there, that they shift their
position, die out, and reappear, that the rate of spreading
alters repeatedly and often ceases altogether, and that
lithospheric plates are broken up into an even greater number of
secondary and tertiary plates.
_All these schemes are characterised by a complete absence of
logic, and of patterns of any kind.
_The impression is given that certain rules of the game have
been invented, and that the aim is to fit reality into these
rules somehow or other. (1980, p. 303)
_Criticism of plate tectonics has increased in line with the
growing number of observational anomalies.
_This paper outlines some of the main problems facing the
theory.
Plates in Motion?
_According to the classical model of plate tectonics,
lithospheric plates creep over a relatively plastic layer of
partly molten rock known as the asthenosphere (or low-velocity
zone).
_According to a modern geological textbook (McGeary and Plummer,
1998), the lithosphere, which comprises the earth's crust and
uppermost mantle, averages about 70 km thick beneath oceans and
is at least 125 km thick beneath continents, while the
asthenosphere extends to a depth of perhaps 200 km.
_It points out that some geologists think that the lithosphere
beneath continents is at least 250 km thick.
_Seismic tomography, which produces three-dimensional images of
the earth's interior, appears to show that the oldest parts of
the continents have deep roots extending to depths of 400 to 600
km, and that the asthenosphere is essentially absent beneath
them.
_McGeary and Plummer (1998) say that these findings cast doubt
on the original, simple lithosphere-asthenosphere model of plate
behavior.
_They do not, however, consider any alternatives.
_Despite the compelling seismotomographic evidence for deep
continental roots (Dziewonski and Anderson, 1984; Dziewonski and
Woodhouse, 1987; Grand, 1987; Lerner-Lam, 1988; Forte,
Dziewonski, and O'Connell, 1995; Gossler and Kind, 1996), some
plate tectonicists have suggested that we just happen to live at
a time when the continents have drifted over colder mantle
(Anderson, Tanimoto, and Zhang, 1992), or that continental roots
are really no more than about 200 km thick, but that they induce
the downwelling of cold mantle material beneath them, giving the
illusion of much deeper roots (Polet and Anderson, 1995).
_However, evidence from seismic-velocity, heat-flow, and gravity
studies has been building up for several decades, showing that
ancient continental shields have very deep roots and that the
low-velocity asthenosphere is very thin or absent beneath them
(e.g. MacDonald, 1963; Jordan, 1975, 1978; Pollack and Chapman,
1977).
_Seismic tomography has merely reinforced the message that
continental cratons, especially those of Archean and Early
Proterozoic age, are "welded" to the underlying mantle, and that
the concept of thin (less than 250-km-thick) lithospheric plates
moving thousands of kilometers over a global asthenosphere is
unrealistic.
_Nevertheless, many textbooks continue to propagate the
simplistic lithosphere-asthenosphere model, and fail to give the
slightest indication that it faces any problems (e.g. McLeish,
1992; Skinner and Porter, 1995; Wicander and Monroe, 1999).
_Geophysical data show that, far from the asthenosphere being a
continuous layer, there are disconnected lenses (asthenolenses),
which are observed only in regions of tectonic activation and
high heat flow.
_Although surface-wave observations suggested that the
asthenosphere was universally present beneath the oceans,
detailed seismic studies show that here, too, there are only
asthenospheric lenses.
_Seismic research has revealed complicated zoning and
inhomogeneity in the upper mantle, and the alternation of layers
with higher and lower velocities and layers of different
quality.
_Individual low-velocity layers are bedded at different depths
in different regions and do not compose a single layer.
_This renders the very concept of the lithosphere ambiguous, at
least that of its base.
_Indeed, the definition of the lithosphere and asthenosphere has
become increasingly blurred with time (Pavlenkova, 1990, 1995,
1996).
_Thus, the lithosphere has a highly complex and irregular
structure.
_Far from being homogeneous, "plates" are actually "a
megabreccia, a 'pudding' of inhomogeneities whose nature, size
and properties vary widely" (Chekunov, Gordienko, and Guterman,
1990, p. 404).
_The crust and uppermost mantle are divided by faults into a
mosaic of separate, jostling blocks of different shapes and
sizes, generally a few hundred kilometers across, and of varying
internal structure and strength.
_Pavlenkova (1990, p. 78) concludes: "This means that the
movement of lithospheric plates over long distances, as single
rigid bodies, is hardly possible.
_Moreover, if we take into account the absence of the
asthenosphere as a single continuous zone, then this movement
seems utterly impossible."
_ She states that this is further confirmed by the strong
evidence that regional geological features, too, are connected
with deep (more than 400 km) inhomogeneities and that these
connections remain stable during long periods of geologic time;
considerable movement between the lithosphere and asthenosphere
would detach near-surface structures from their deep mantle
roots.
_Plate tectonicists who accept the evidence for deep continental
roots have proposed that plates may extend to and glide along
the 400-km or even 670-km seismic discontinuity (Seyfert, 1998;
Jordan, 1975, 1978, 1979).
_Jordan, for instance, suggested that the oceanic lithosphere
moves on the classical low-velocity zone, while the continental
lithosphere moves along the 400-km discontinuity.
_However, there is no certainty that a superplastic zone exists
at this discontinuity, and no evidence has been found of a shear
zone connecting the two decoupling layers along the trailing
edge of continents (Lowman, 1985).
_Moreover, even under the oceans there appears to be no
continuous asthenosphere.
_Finally, the movement of such thick "plates" poses an even
greater problem than that of thin lithospheric plates.
_The driving force of plate movements was initially claimed to
be mantle-deep convection currents welling up beneath midocean
ridges, with downwelling occurring beneath ocean trenches.
_Since the existence of layering in the mantle was considered to
render whole-mantle convection unlikely, two-layer convection
models were also proposed.
_Jeffreys (1974) argued that convection cannot take place
because it is a self-damping process, as described by the
Lomnitz law.
_Plate tectonicists expected seismic tomography to provide clear
evidence of a well-organized convection-cell pattern, but it has
actually provided strong evidence against the existence of
large, plate-propelling convection cells in the upper mantle
(Anderson, Tanimoto, and Zhang, 1992).
_Many geologists now think that mantle convection is a result of
plate motion rather than its cause, and that it is shallow
rather than mantle deep (McGeary and Plummer, 1998).
_The favored plate-driving mechanisms at present are
"ridge-push" and "slab-pull," though their adequacy is very much
in doubt.
_Slab-pull is believed to be the dominant mechanism, and refers
to the gravitational subsidence of subducted slabs.
_However, it will not work for plates that are largely
continental, or that have leading edges that are continental,
because continental crust cannot be bodily subducted due to its
low density, and it seems utterly unrealistic to imagine that
ridge-push from the Mid-Atlantic Ridge alone could move the
120°-wide Eurasian plate (Lowman, 1986).
_Moreover, evidence for the long-term weakness of large rock
masses casts doubt on the idea that edge forces can be
transmitted from one margin of a "plate" to its interior or
opposite margin (Keith, 1993).
_Thirteen major plates are currently recognized, ranging in size
from about 400 by 2500 km to 10,000 by 10,000 km, together with
a proliferating number of microplates (over 100 so far).
_Van Andel (1998) writes: Where plate boundaries adjoin
continents, matters often become very complex and have demanded
an ever denser thicket of ad hoc modifications and amendments to
the theory and practice of plate tectonics in the form of
microplates, obscure plate boundaries, and exotic terranes.
_A good example is the Mediterranean, where the collisions
between Africa and a swarm of microcontinents have produced a
tectonic nightmare that is far from resolved.
_More disturbingly, some of the present plate boundaries,
especially in the eastern Mediterranean, appear to be so diffuse
and so anomalous that they cannot be compared to the three types
of plate boundaries of the basic theory.
_Plate boundaries are identified and defined mainly on the basis
of earthquake and volcanic activity.
_The close correspondence between plate edges and belts of
earthquakes and volcanoes is therefore to be expected and can
hardly be regarded as one of the "successes" of plate tectonics
(McGeary and Plummer, 1998).
_Moreover, the simple pattern of earthquakes around the Pacific
Basin on which plate-tectonics models have hitherto been based
has been seriously undermined by more recent studies showing a
surprisingly large number of earthquakes in deep-sea regions
previously thought to be aseismic (Storetvedt, 1997).
_Another major problem is that several "plate boundaries" are
purely theoretical and appear to be nonexistent, including the
northwest Pacific boundary of the Pacific, North American, and
Eurasian plates, the southern boundary of the Philippine plate,
part of the southern boundary of the Pacific plate, and most of
the northern and southern boundaries of the South American plate
(Stanley, 1989).
Continental Drift
_Geological field mapping provides evidence for horizontal
crustal movements of up to several hundred kilometers (Jeffreys,
1976).
_Plate tectonics, however, claims that continents have moved up
to 7000 km or more since the alleged breakup of Pangaea.
_Measurements using space-geodetic techniques -- very long
baseline interferometry (VLBI), satellite laser-ranging (SLR),
and the global positioning system (GPS) -- have been hailed by
some workers as having proved plate tectonics.
_Such measurements provide a guide to crustal strains, but do
not provide evidence for plate motions of the kind predicted by
plate tectonics unless the relative motions predicted among all
plates are observed.
_However, many of the results have shown no definite pattern,
and have been confusing and contradictory, giving rise to a
variety of ad-hoc hypotheses (Fallon and Dillinger, 1992; Gordon
and Stein, 1992; Smith et al., 1994).
_Japan and North America appear, as predicted, to be approaching
each other, but distances from the Central South American Andes
to Japan or Hawaii are more or less constant, whereas plate
tectonics predicts significant separation (Storetvedt, 1997).
_Trans-Atlantic drift has not been demonstrated, because
baselines within North America and western Europe have failed to
establish that the plates are moving as rigid units; they
suggest in fact significant intraplate deformation (Lowman,
1992b; James, 1994).
_Space-geodetic measurements to date have therefore not
confirmed plate tectonics.
_Moreover, they are open to alternative explanations (e.g.
Meyerhoff et al., 1996a; Storetvedt, 1997; Carey, 1994).
_It is clearly a hazardous exercise to extrapolate present
crustal movements tens or hundreds of millions of years into the
past or future.
_Indeed, geodetic surveys across "rift" zones (e.g. in Iceland
and East Africa) have failed to detect any consistent and
systematic widening as postulated by plate tectonics (Keith,
1993).
Fits and Misfits
_A "compelling" piece of evidence that all the continents were
once united in one large landmass is said to be the fact that
they can be fitted together like pieces of a jigsaw puzzle.
_Many reconstructions have been attempted (e.g. Bullard,
Everett, and Smith, 1965; Nafe and Drake, 1969; Dietz and
Holden, 1970; Smith and Hallam, 1970; Tarling, 1971; Barron,
Harrison, and Hay, 1978; Smith, Hurley, and Briden, 1981;
Scotese, Gagahan, and Larson, 1988), but none are entirely
acceptable.
_In the Bullard, Everett, and Smith (1965) computer-generated
fit, for example, there are a number of glaring omissions.
_The whole of Central America and much of southern Mexico are
left out, despite the fact that extensive areas of Paleozoic and
Precambrian continental rocks occur there.
_This region of some 2,100,000 km² overlaps South America in a
region consisting of a craton at least 2 billion years old.
_The entire West Indian archipelago has also been omitted.
_In fact, much of the Caribbean is underlain by ancient
continental crust, and the total area involved, 300,000 km²,
overlaps Africa (Meyerhoff and Hatten, 1974).
_The Cape Verde Islands-Senegal basin, too, is underlain by
ancient continental crust, creating an additional overlap of
800,000 km².
_Several major submarine structures that appear to be of
continental origin are ignored in the Bullard, Everett, and
Smith fit, including the Faeroe-Iceland-Greenland Ridge, Jan
Mayen Ridge, Walvis Ridge, Rio Grande Rise, and the Falkland
Plateau.
_However, the Rockall Plateau was included for the sole reason
that it could be "slotted in."
_The Bullard fit postulates an east-west shear zone through the
present Mediterranean and requires a rotation of Spain, but
field geology does not support either of these suppositions
(Meyerhoff and Meyerhoff, 1974a).
_Even the celebrated fit of South America and Africa is
problematic as it is impossible to match all parts of the
coastlines simultaneously; for instance, there is a gap between
Guyana and Guinea (Eyles and Eyles, 1993).
_Like the Bullard, Everett, and Smith (1965) fit, the Smith and
Hallam (1970) reconstruction of the Gondwanaland continents is
based on the 500-fathom depth contour.
_The South Orkneys and South Georgia are omitted, as is
Kerguelen Island in the Indian Ocean, and there is a large gap
west of Australia.
_Fitting India against Australia, as in other fits, leaves a
corresponding gap in the western Indian Ocean (Hallam, 1976).
_Dietz and Holden (1970) based their fit on the 1000-fathom
(2-km) contour, but they still had to omit the Florida-Bahamas
platform, ignoring the evidence that it predates the alleged
commencement of drift.
_In many regions the boundary between continental and oceanic
crust appears to occur beneath oceanic depths of 2-4 km or more
(Hallam, 1979), and in some places the ocean-continent
transition zone is several hundred kilometers wide (Van der
Linden, 1977).
_This means that any reconstructions based on arbitrarily
selected depth contours are flawed.
_Given the liberties that drifters have had to take to obtain
the desired continental matches, their computer-generated fits
may well be a case of "garbage in, garbage out" (Le Grand,
1988).
_The similarities of rock types and geological structures on
coasts that were supposedly once juxtaposed are hailed by
drifters as further evidence that the continents were once
joined together.
_However, they rarely mention the many geological
dissimilarities.
_For instance, western Africa and northern Brazil were
supposedly once in contact, yet the structural trends of the
former run N-S, while those of the latter run E-W (Storetvedt,
1997).
_Some predrift reconstructions show peninsular India against
western Antarctica, yet Permian Indian basins do not correspond
geographically or in sequence to the western Australian basins
(Dickins and Choi, 1997).
_Gregory (1929) held that the geological resemblances of
opposing Atlantic coastlines are due to the areas having
belonged to the same tectonic belt, but that the differences are
sufficient to show that the areas were situated in distant parts
of the belt.
_Bucher (1933) showed that the paleontological and geological
similarities between the eastern Alps and central Himalayas,
4000 miles apart, are just as remarkable as those between the
Argentine and South Africa, separated by the same distance.
_The approximate parallelism of the coastlines of the Atlantic
Ocean may be due to the boundaries between the continents and
oceans having been formed by deep faults, which tend to be
grouped into parallel systems (Beloussov, 1980).
_Moreover, the curvature of continental contours is often so
similar that many of them can be joined together if they are
given the necessary rotation.
_Lyustikh (1967) gave examples of 15 shorelines that can be
fitted together quite well even though they can never have been
in juxtaposition.
_Voisey (1958) showed that eastern Australia fits well with
eastern North America if Cape York is placed next to Florida.
_He pointed out that the geological and paleontological
similarities are remarkable, probably due to the similar
tectonic backgrounds of the two regions.
Paleomagnetic Pitfalls
_One of the main props of continental drift is paleomagnetism --
the study of the magnetism of ancient rocks and sediments.
_The inclination and declination of fossil magnetism can be used
to infer the location of a virtual magnetic pole relative to the
location of the sample in question.
_When virtual poles are determined from progressively older
rocks from the same continent, the poles appear to wander with
time.
_Joining the former, averaged pole positions generates an
apparent polar wander path.
_Different continents yield different polar wander paths, and
from this it has been concluded that the apparent wandering of
the magnetic poles is caused by the actual wandering of the
continents over the earth's surface.
_The possibility that there has been some degree of true polar
wander -- i.e. a shift of the whole earth relative to the
rotation axis (the axial tilt remaining the same) -- has not,
however, been ruled out.
_That paleomagnetism can be unreliable is well established
(Barron, Harrison, and Hay, 1978; Meyerhoff and Meyerhoff,
1972).
_For instance, paleomagnetic data imply that during the
mid-Cretaceous Azerbaijan and Japan were in the same place
(Meyerhoff, 1970a)! The literature is in fact bursting with
inconsistencies (Storetvedt, 1997).
_Paleomagnetic studies of rocks of different ages suggest a
different polar wander path not only for each continent, but
also for different parts of each continent.
_When individual paleomagnetic pole positions, rather than
averaged curves, are plotted on world maps, the scatter is huge,
often wider than the Atlantic.
_Furthermore, paleomagnetism can determine only paleolatitude,
not paleolongitude.
_Consequently, it cannot be used to prove continental drift.
_Paleomagnetism is plagued with uncertainties.
_Merrill, McElhinny, and McFadden (1996, p. 69) state: "there
are numerous pitfalls that await the unwary: first, in sorting
out the primary magnetization from secondary magnetizations
(acquired subsequent to formation), and second, in extrapolating
the properties of the primary magnetization to those of the
earth's magnetic field."
_The interpretation of paleomagnetic data is founded on two
basic assumptions:
1. when rocks are formed, they are magnetized in the direction
of the geomagnetic field existing at the time and place of their
formation, and the acquired magnetization is retained in the
rocks at least partially over geologic time;
2. the geomagnetic field averaged for any time period of the
order of 105 years (except magnetic-reversal epochs) is a dipole
field oriented along the earth's rotation axis.
_Both these assumptions are questionable.
_The gradual northward shift of paleopole "scatter ellipses"
through time and the gradual reduction in the diameters of the
ellipses suggest that remanent magnetism becomes less stable
with time.
_Rock magnetism is subject to modification by later magnetism,
weathering, metamorphism, tectonic deformation, and chemical
changes.
_Moreover, the geomagnetic field at the present time deviates
substantially from that of a geocentric axial dipole.
_The magnetic axis is tilted by about 11° to the rotation axis,
and on some planets much greater offsets are found: 46.8° in the
case of Neptune, and 58.6° in the case of Uranus (Merrill,
McElhinny, and McFadden, 1996).
_Nevertheless, because earth's magnetic field undergoes
significant long-term secular variation (e.g.
_a westward drift), it is thought that the time-averaged field
will closely approximate a geocentric axial dipole.
_However, there is strong evidence that the geomagnetic field
had long-term nondipole components in the past, though they have
largely been neglected (Van der Voo, 1998; Kent and Smethurst,
1998).
_To test the axial nature of the geomagnetic field in the past,
paleoclimatic data have to be used.
_However, several major paleoclimatic indicators, along with
paleontological data, provide powerful evidence against
continental-drift models, and therefore against the current
interpretation of paleomagnetic data (see below).
_It is possible that the magnetic poles have wandered
considerably with respect to the geographic poles in former
times.
_Also, if in past geological periods there were stable magnetic
anomalies of the same intensity as the present-day East Asian
anomaly (or slightly more intensive), this would render the
geocentric axial dipole hypothesis invalid (Beloussov, 1990).
_Regional or semi-global magnetic fields might be generated by
vortex-like cells of thermal-magmatic energy, rising and falling
in the earth's mantle (Pratsch, 1990).
_Another important factor may be magnetostriction -- the
alteration of the direction of magnetization by directed stress
(Jeffreys, 1976; Munk and MacDonald, 1975).
_Some workers have shown that certain discordant paleomagnetic
results that could be explained by large horizontal movements
can be explained equally well by vertical block rotations and
tilts and by inclination shallowing resulting from sediment
compaction (Butler et al., 1989; Dickinson and Butler, 1998;
Irving and Archibald, 1990; Hodych and Bijaksana, 1993).
_Storetvedt (1992, 1997) has developed a model known as global
wrench tectonics in which paleomagnetic data are explained by
in-situ horizontal rotations of continental blocks, together
with true polar wander.
_The possibility that a combination of these factors could be at
work simultaneously significantly undermines the use of
paleomagnetism to support continental drift.
Drift versus Geology
_The opening of the Atlantic Ocean allegedly began in the
Cretaceous by the rifting apart of the Eurasian and American
plates.
_However, on the other side of the globe, northeastern Eurasia
is joined to North America by the Bering-Chukotsk shelf, which
is underlain by Precambrian continental crust that is continuous
and unbroken from Alaska to Siberia.
_Geologically these regions constitute a single unit, and it is
unrealistic to suppose that they were formerly divided by an
ocean several thousand kilometers wide, which closed to
compensate for the opening of the Atlantic.
_If a suture is absent there, one ought to be found in Eurasia
or North America, but no such suture appears to exist
(Beloussov, 1990; Shapiro, 1990).
_If Baffin Bay and the Labrador Sea had formed by Greenland and
North America drifting apart, this would have produced hundreds
of kilometers of lateral offset across the Nares Strait between
Greenland and Ellesmere Island, but geological field studies
reveal no such offset (Grant, 1980, 1992).
_Greenland is separated from Europe west of Spitsbergen by only
50-75 km at the 1000-fathom depth contour, and it is joined to
Europe by the continental Faeroe-Iceland-Greenland Ridge
(Meyerhoff, 1974).
_All these facts rule out the possibility of east-west drift in
the northern hemisphere.
_Geology indicates that there has been a direct tectonic
connection between Europe and Africa across the zones of
Gibraltar and Rif on the one hand, and Calabria and Sicily on
the other, at least since the end of the Paleozoic,
contradicting plate-tectonic claims of significant displacement
between Europe and Africa during this period (Beloussov, 1990).
_Plate tectonicists hold widely varying opinions on the Middle
East region.
_Some advocate the former presence of two or more plates, some
postulate several microplates, others support island-arc
interpretations, and a majority favor the existence of at least
one suture zone that marks the location of a continent-continent
collision.
_Kashfi (1992, p. 119) comments: "Nearly all of these hypotheses
are mutually exclusive.
_Most would cease to exist if the field data were honored.
_These data show that there is nothing in the geologic record to
support a past separation of Arabia-Africa from the remainder of
the Middle East."
_India supposedly detached itself from Antarctica sometime
during the Mesozoic, and then drifted northeastward up to 9000
km, over a period of up to 200 million years, until it finally
collided with Asia in the mid-Tertiary, pushing up the Himalayas
and the Tibetan Plateau.
_That Asia happened to have an indentation of approximately the
correct shape and size and in exactly the right place for India
to "dock" into would amount to a remarkable coincidence
(Mantura, 1972).
_There is, however, overwhelming geological and paleontological
evidence that India has been an integral part of Asia since
Proterozoic or earlier time (Chatterjee and Hotton, 1986; Ahmad,
1990; Saxena and Gupta, 1990; Meyerhoff et al., 1991).
_There is also abundant evidence that the Tethys Sea in the
region of the present Alpine-Himalayan orogenic belt was never a
deep, wide ocean but rather a narrow, predominantly shallow,
intracontinental seaway (Bhat, 1987; Dickins, 1987, 1994c;
McKenzie, 1987; Stöcklin, 1989).
_If the long journey of India had actually occurred, it would
have been an isolated island-continent for millions of years --
sufficient time to have evolved a highly distinct endemic fauna.
_However, the Mesozoic and Tertiary faunas show no such
endemism, but indicate instead that India lay very close to Asia
throughout this period, and not to Australia and Antarctica
(Chatterjee and Hotton, 1986).
_The stratigraphic, structural, and paleontological continuity
of India with Asia and Arabia means that the supposed "flight of
India" is no more than a flight of fancy.
_A striking feature of the oceans and continents today is that
they are arranged antipodally: the Arctic Ocean is precisely
antipodal to Antarctica; North America is exactly antipodal to
the Indian Ocean; Europe and Africa are antipodal to the central
area of the Pacific Ocean; Australia is antipodal to the small
basin of the North Atlantic; and the South Atlantic corresponds
-- though less exactly -- to the eastern half of Asia (Gregory,
1899, 1901; Bucher, 1933; Steers, 1950).
_Only 7% of the earth's surface does not obey the antipodal
rule.
_If the continents had slowly drifted thousands of kilometers to
their present positions, the antipodal arrangement of land and
water would have to be regarded as purely coincidental.
_Harrison et al. (1983) calculated that there is 1 chance in 7
that this arrangement is the result of a random process.
Paleoclimatology
_The paleoclimatic record is preserved from Proterozoic time to
the present in the geographic distribution of evaporites,
carbonate rocks, coals, and tillites.
_The locations of these paleoclimatic indicators are best
explained by stable rather than shifting continents, and by
periodic changes in climate, from globally warm or hot to
globally cool (Meyerhoff and Meyerhoff, 1974a; Meyerhoff et al.,
1996b).
_For instance, 95% of all evaporites -- a dry-climate indicator
-- from the Proterozoic to the present lie in regions that now
receive less than 100 cm of rainfall per year, i.e. in today's
dry-wind belts.
_The evaporite and coal zones show a pronounced northward offset
similar to today's northward offset of the thermal equator.
_Shifting the continents succeeds at best in explaining local or
regional paleoclimatic features for a particular period, and
invariably fails to explain the global climate for the same
period.
_In the Carboniferous and Permian, glaciers covered parts of
Antarctica, South Africa, South America, India, and Australia.
_Drifters claim that this glaciation can be explained in terms
of Gondwanaland, which was then situated near the south pole.
_However, the Gondwanaland hypothesis defeats itself in this
respect because large areas that were glaciated during this
period would be removed too far inland for moist ocean-air
currents to reach them.
_Glaciers would have formed only at its margins, while the
interior would have been a vast, frigid desert (Meyerhoff,
1970a; Meyerhoff and Teichert, 1971).
_Shallow epicontinental seas within Pangaea could not have
provided the required moisture because they would have been
frozen during the winter months.
_This glaciation is easier to explain in terms of the
continents' present positions: nearly all the continental ice
centers were adjacent to or near present coastlines, or in high
plateaus and/or mountainlands not far from present coasts.
_Drifters say that the continents have shifted little since the
start of the Cenozoic (some 65 million years ago), yet this
period has seen significant alterations in climatic conditions.
_Even since Early Pliocene time the width of the temperate zone
has changed by more than 15° (1650 km) in both the northern and
southern hemispheres.
_The uplift of the Rocky Mountains and Tibetan Plateau appears
to have been a key factor in the Late Cenozoic climatic
deterioration (Ruddiman and Kutzbach, 1989; Manabe and Broccoli,
1990).
_To decide whether past climates are compatible with the present
latitudes of the regions concerned, it is clearly essential to
take account of vertical crustal movements, which can bring
about significant changes in atmospheric and oceanic circulation
patterns by altering the topography of the continents and ocean
floor, and the distribution of land and sea (Dickins, 1994a;
Meyerhoff, 1970b; Brooks, 1949).
Biopaleogeography
_Meyerhoff et al. (1996b) showed in a detailed study that most
major biogeographical boundaries, based on floral and faunal
distributions, do not coincide with the partly
computer-generated plate boundaries postulated by plate
tectonics.
_Nor do the proposed movements of continents correspond with the
known, or necessary, migration routes and directions of
biogeographical boundaries.
_In most cases, the discrepancies are very large, and not even
an approximate match can be claimed.
_The authors comment: "What is puzzling is that such major
inconsistencies between plate tectonic postulates and field
data, involving as they do boundaries that extend for thousands
of kilometers, are permitted to stand unnoticed, unacknowledged,
and unstudied" (p. 3).
_The known distributions of fossil organisms are more consistent
with an earth model like that of today than with
continental-drift models, and more migration problems are raised
by joining the continents in the past than by keeping them
separated (Smiley, 1974, 1976, 1992; Teichert, 1974; Khudoley,
1974; Meyerhoff and Meyerhoff, 1974a; Teichert and Meyerhoff,
1972).
_It is unscientific to select a few faunal identities and ignore
the vastly greater number of faunal dissimilarities from
different continents which were supposedly once joined.
_The widespread distribution of the Glossopteris flora in the
southern continents is frequently claimed to support the former
existence of Gondwanaland, but it is rarely pointed out that
this flora has also been found in northeast Asia (Smiley, 1976).
_Some of the paleontological evidence appears to require the
alternate emergence and submergence of land dispersal routes
only after the supposed breakup of Pangaea.
_For example, mammal distribution indicates that there were no
direct physical connections between Europe and North America
during Late Cretaceous and Paleocene times, but suggests a
temporary connection with Europe during the Eocene (Meyerhoff
and Meyerhoff, 1974a).
_Continental drift, on the other hand, would have resulted in an
initial disconnection with no subsequent reconnection.
_A few drifters have recognized the need for intermittent land
bridges after the supposed separation of the continents (e.g.
Tarling, 1982; Briggs, 1987).
_Various oceanic ridges, rises, and plateaus could have served
as land bridges, as many are known to have been partly above
water at various times in the past.
_It is also possible that these land bridges formed part of
larger former landmasses in the present oceans (see below).
Seafloor Spreading and Subduction
_According to the seafloor-spreading hypothesis, new oceanic
lithosphere is generated at midocean ridges ("divergent plate
boundaries") by the upwelling of molten material from the
earth's mantle, and as the magma cools it spreads away from the
flanks of the ridges.
_The horizontally moving plates are said to plunge back into the
mantle at ocean trenches or "subduction zones" ("convergent
plate boundaries").
_The melting of the descending slab is believed to give rise to
the magmatic-volcanic arcs that lie adjacent to certain
trenches.
Seafloor Spreading
_The ocean floor is far from having the uniform characteristics
that conveyor-type spreading would imply (Keith, 1993).
_Although averaged surface-wave data seemed to confirm that the
oceanic lithosphere was symmetrical in relation to the ridge
axis and increased in thickness with distance from the axial
zone, more detailed seismic research has contradicted this
simple model.
_It has shown that the mantle is asymmetrical in relation to the
midocean ridges and has a complicated mosaic structure
independent of the strike of the ridge.
_Several low-velocity zones (asthenolenses) occur in the oceanic
mantle, but it is difficult to establish any regularity between
the depth of the zones and their distance from the midocean
ridge (Pavlenkova, 1990).
_Boreholes drilled in the Atlantic, Indian, and Pacific Oceans
have shown the extensive distribution of shallow-water sediments
ranging from Triassic to Quaternary.
_The spatial distribution of shallow-water sediments and their
vertical arrangement in some of the sections refute the
spreading mechanism for the formation of oceanic lithosphere
(Ruditch, 1990).
_The evidence implies that since the Jurassic, the present
oceans have undergone large-amplitude subsidences, and that this
occurred mosaically rather than showing a systematic
relationship with distance from the ocean ridges.
_Younger, shallow-water sediments are often located farther from
the axial zones of the ridges than older ones -- the opposite of
what is required by the plate-tectonics model, which postulates
that as newly-formed oceanic lithosphere moves away from the
spreading axis and cools, it gradually subsides to greater
depths.
_Furthermore, some areas of the oceans appear to have undergone
continuous subsidence, whereas others underwent alternating
subsidence and elevation.
_The height of the ridge along the Romanche fracture zone in the
equatorial Atlantic is 1 to 4 km above that expected by
seafloor-spreading models.
_Large segments of it were close to or above sea level only 5
million years ago, and subsequent subsidence has been one order
of magnitude faster than that predicted by plate tectonics
(Bonatti and Chermak, 1981).
_According to the seafloor-spreading model, heat flow should be
highest along ocean ridges and fall off steadily with increasing
distance from the ridge crests.
_Actual measurements, however, contradict this simple picture:
ridge crests show a very large scatter in heat-flow magnitudes,
and there is generally little difference in thermal flux between
the ridge and the rest of the ocean (Storetvedt, 1997; Keith,
1993).
_All parts of the Indian Ocean display a cold and rather
featureless heat-flow picture except the Central Indian Basin.
_The broad region of intense tectonic deformation in this basin
indicates that the basement has a block structure, and presents
a major puzzle for plate tectonics, especially since it is
located in a "midplate" setting.
_Smoot and Meyerhoff (1995) have shown that nearly all published
charts of the world's ocean floors have been drawn deliberately
to reflect the predictions of the plate-tectonics hypothesis.
_For example, the Atlantic Ocean floor is unvaryingly shown to
be dominated by a sinuous, north-south midocean ridge, flanked
on either side by abyssal plains, cleft at its crest by a rift
valley, and offset at more or less regular 40- to 60-km
intervals by east-west-striking fracture zones.
_New, detailed bathymetric surveys indicate that this
oversimplified portrayal of the Atlantic Basin is largely wrong,
yet the most accurate charts now available are widely ignored
because they do not conform to plate-tectonic preconceptions.
_According to plate tectonics, the offset segments of
"spreading" oceanic ridges should be connected by "transform
fault" plate boundaries.
_Since the late 1960s, it has been claimed that first-motion
studies in ocean fracture zones provide overwhelming support for
the concept of transform faults.
_The results of these seismic surveys, however, were never
clear-cut, and contradictory evidence and alternative
explanations have been ignored (Storetvedt, 1997; Meyerhoff and
Meyerhoff, 1974a).
_Instead of being continuous and approximately parallel across
the full width of each ridge, ridge-transverse fracture zones
tend to be discontinuous, with many unpredicted bends,
bifurcations, and changes in strike.
_In places, the fractures are diagonal rather than perpendicular
to the ridge, and several parts of the ridge have no important
fracture zones or even traces of them.
_For instance, they are absent from a 700-km-long portion of the
Mid-Atlantic Ridge between the Atlantis and Kane fracture zones.
_There is a growing recognition that the fracture patterns in
the Atlantic "show anomalies that are neither predicted by nor
... yet built into plate tectonic understanding" (Shirley,
1998a, b).
_Side-scanning radar images show that the midocean ridges are
cut by thousands of long, linear, ridge-parallel fissures,
fractures, and faults.
_This strongly suggests that the ridges are underlain at shallow
depth by interconnected magma channels, in which semi-fluid lava
moves horizontally and parallel with the ridges rather than at
right-angles to them.
_The fault pattern observed is therefore totally different from
that predicted by plate tectonics, and it cannot be explained by
upwelling mantle diapirs as some plate tectonicists have
proposed (Meyerhoff et al., 1992a).
_A zone of thrust faults, 300-400 km wide, has been discovered
flanking the Mid-Atlantic Ridge over a length of 1000 km
(Antipov et al., 1990).
_Since it was produced under conditions of compression, it
contradicts the plate-tectonic hypothesis that midocean ridges
are dominated by tension.
_In Iceland, the largest landmass astride the Mid-Atlantic
Ridge, the predominant stresses in the axial zone are likewise
compressive rather than extensional (Keith, 1993).
_Earthquake data compiled by Zoback et al. (1989) provide
further evidence that ocean ridges are characterized by
widespread compression, whereas recorded tensional earthquake
activity associated with these ridges is rarer.
_The rough topography and strong tectonic deformation of much of
the ocean ridges, especially in the Atlantic and Indian Oceans,
suggest that, instead of being "spreading centers," they are a
type of foldbelt (Storetvedt, 1997).
_The continents and oceans are covered with a network of major
structures or lineaments, many dating from the Precambrian,
along which tectonic and magmatic activity and associated
mineralization take place (Gay, 1973; Katterfeld and Charushin,
1973; O'Driscoll, 1980; Wezel, 1992; Anfiloff, 1992; Dickins and
Choi, 1997).
_The oceanic lineaments are not readily compatible with seafloor
spreading and subduction, and plate tectonics shows little
interest in them.
_GEOSAT data and SASS multibeam sonar data show that there are
NNW-SSE and WSW-ENE megatrends in the Pacific Ocean, composed
primarily of fracture zones and linear seamount chains, and
these orthogonal lineaments naturally intersect (Smoot, 1997b,
1998a, b, 1999).
_This is a physical impossibility in plate tectonics, as
seamount chains supposedly indicate the direction of plate
movement, and plates would therefore have to move in two
directions at once! No satisfactory plate-tectonic explanation
of any of these megatrends has been proposed outside the realm
of ad-hoc "microplates," and they are largely ignored.
_The orthogonal lineaments in the Atlantic Ocean, Indian Ocean,
and Tasmanian Sea are also ignored (Choi, 1997, 1999a, c).
Age of the Seafloor
_The oldest known rocks from the continents are just under 4
billion years old, whereas -- according to plate tectonics --
none of the ocean crust is older than 200 million years
(Jurassic).
_This is cited as conclusive evidence that oceanic lithosphere
is constantly being created at midocean ridges and consumed in
subduction zones.
_There is in fact abundant evidence against the alleged youth of
the ocean floor, though geological textbooks tend to pass over
it in silence.
_The oceanic crust is commonly divided into three main layers:
layer 1 consists of ocean floor sediments and averages 0.5 km in
thickness; layer 2 consists largely of basalt and is 1.0 to 2.5
km thick; and layer 3 is assumed to consist of gabbro and is
about 5 km thick.
_Scientists involved in the Deep Sea Drilling Project (DSDP)
have given the impression that the basalt (layer 2) found at the
base of many deep-sea drillholes is basement, and that there are
no further, older sediments below it.
_However, the DSDP scientists were apparently motivated by a
strong desire to confirm seafloor spreading (Storetvedt, 1997).
_Of the first 429 sites drilled (1968-77), only 165 (38%)
reached basalt, and some penetrated more than one basalt.
_All but 12 of the 165 basalt penetrations were called basement,
including 19 sites where the upper contact of the basalt with
the sediments was baked (Meyerhoff et al., 1992a).
_Baked contacts suggest that the basalt is an intrusive sill,
and in some cases this has been confirmed, as the basalts turned
out to have radiometric dates younger than the overlying
sediments (e.g. Macdougall, 1971).
_101 sediment-basalt contacts were never recovered in cores, and
therefore never actually seen, yet they were still assumed to be
depositional contacts.
_In 33 cases depositional contacts were observed, but the basalt
sometimes contained sedimentary clasts, suggesting that there
might be older sediments below.
_Indeed, boreholes that have penetrated layer 2 to some depth
have revealed an alternation of basalts and sedimentary rocks
(Hall and Robinson, 1979; Anderson et al., 1982).
_Kamen-Kaye (1970) warned that before drawing conclusions on the
youth of the ocean floor, rocks must be penetrated to depths of
up to 5 km to see whether there are Triassic, Paleozoic, or
Precambrian sediments below the so-called basement.
_Plate tectonics predicts that the age of the oceanic crust
should increase systematically with distance from the midocean
ridge crests.
_Claims by DSDP scientists to have confirmed this are not
supported by a detailed review of the drilling results.
_The dates exhibit a very large scatter, which becomes even
larger if dredge hauls are included.
_On some marine magnetic anomalies the age scatter is tens of
millions of years (Meyerhoff et al., 1992a).
_On one seamount just west of the crest of the East Pacific
Rise, the radiometric dates range from 2.4 to 96 million years.
_Although a general trend is discernible from younger sediments
at ridge crests to older sediments away from them, this is in
fact to be expected, since the crest is the highest and most
active part of the ridge; older sediments are likely to be
buried beneath younger volcanic rocks.
_The basalt layer in the ocean crust suggests that magma
flooding was once ocean-wide, but volcanism was subsequently
restricted to an increasingly narrow zone centered on the ridge
crests.
_Such magma floods were accompanied by progressive crustal
subsidence in large sectors of the present oceans, beginning in
the Jurassic (Keith, 1993; Beloussov, 1980).
_The numerous finds in the Atlantic, Pacific, and Indian Oceans
of rocks far older than 200 million years, many of them
continental in nature, provide strong evidence against the
alleged youth of the underlying crust.
_In the Atlantic, rock and sediment age should range from
Cretaceous (120 million years) adjacent to the continents to
very recent at the ridge crest.
_During legs 37 and 43 of the DSDP, Paleozoic and Proterozoic
igneous rocks were recovered in cores on the Mid-Atlantic Ridge
and the Bermuda Rise, yet not one of these occurrences of
ancient rocks was mentioned in the Cruise Site Reports or Cruise
Synthesis Reports (Meyerhoff et al., 1996a).
_Aumento and Loncarevic (1969) reported that 75% of 84 rock
samples dredged from the Bald Mountain region just west of the
Mid-Atlantic Ridge crest at 45°N consisted of continental-type
rocks, and commented that this was a "remarkable phenomenon" --
so remarkable, in fact, that they decided to classify these
rocks as "glacial erratics" and to give them no further
consideration.
_Another way of dealing with "anomalous" rock finds is to
dismiss them as ship ballast.
_However, the Bald Mountain locality has an estimated volume of
80 km³, so it is hardly likely to have been rafted out to sea on
an iceberg or dumped by a ship! It consists of granitic and
silicic metamorphic rocks ranging in age from 1690 to 1550
million years, and is intruded by 785-million-year mafic rocks
(Wanless et al., 1968).
_Ozima et al. (1976) found basalts of Middle Jurassic age (169
million years) at the junction of the rift valley of the
Mid-Atlantic Ridge and the Atlantis fracture zone (30°N), an
area where basalt should theoretically be extremely young, and
stated that they were unlikely to be ice-rafted rocks.
_Van Hinte and Ruffman (1995) concluded that Paleozoic
limestones dredged from Orphan Knoll in the northwest Atlantic
were in situ and not ice rafted.
_In another attempt to explain away anomalously old rocks and
anomalously shallow or emergent crust in certain parts of the
ridges, some plate tectonicists have argued that "nonspreading
blocks" can be left behind during rifting, and that the
spreading axis and related transform faults can jump from place
to place (e.g. Bonatti and Honnorez, 1971; Bonatti and Crane,
1982; Bonatti, 1990).
_This hypothesis was invoked by Pilot et al. (1998) to explain
the presence of zircons with ages of 330 and 1600 million years
in gabbros beneath the Mid-Atlantic Ridge near the Kane fracture
zone.
_Yet another way of dealing with anomalous rock ages is to
reject them as unreliable.
_For instance, Reynolds and Clay (1977), reporting on a
Proterozoic date (635 million years) near the crest of the
Mid-Atlantic Ridge, wrote that the age must be wrong because the
theoretical age of the site was only about 10 million years.
_Paleozoic trilobites and graptolites have been dredged from the
King's Trough area, on the opposite side of the Mid-Atlantic
Ridge to Bald Mountain, and at several localities near the
Azores (Furon, 1949; Smoot and Meyerhoff, 1995).
_Detailed surveys of the equatorial segment of the Mid-Atlantic
Ridge have provided a wide variety of data contradicting the
seafloor-spreading model, including numerous shallow-water and
continental rocks, with ages up to 3.74 billion years (Udintsev,
1996; Udintsev et al., 1993; Timofeyev et al., 1992).
_Melson, Hart, and Thompson (1972), studying St. Peter and
Paul's Rocks at the crest of the Mid-Atlantic Ridge just north
of the equator, found an 835-million-year rock associated with
other rocks giving 350-, 450-, and 2000-million-year ages,
whereas according to the seafloor-spreading model the rock
should have been 35 million years.
_Numerous igneous and metamorphic rocks giving late Precambrian
and Paleozoic radiometric ages have been dredged from the crests
of the southern Mid-Atlantic, Mid-Indian, and Carlsberg ridges
(Afanas'yev et al., 1967).
_Precambrian and Paleozoic granites have been found in several
"oceanic" plateaus and islands with anomalously thick crusts,
including Rockall Plateau, Agulhas Plateau, the Seychelles, the
Obruchev Rise, Papua New Guinea, and the Paracel Islands
(Ben-Avraham et al., 1981; Sanchez Cela, 1999).
_In many cases, structural and petrological continuity exists
between continents and anomalous "oceanic" crusts -- a fact
incompatible with seafloor spreading; this applies, for example,
in the North Atlantic, where there is a continuous sialic
basement, partly of Precambrian age, from North America to
Europe.
_Major Precambrian lineaments in Australia and South America
continue into the ocean floors, implying that the "oceanic"
crust is at least partly composed of Precambrian rocks, and this
has been confirmed by deep-sea dredging, drilling, and seismic
data, and by evidence for submerged continental crust (ancient
paleolands) in the present southeast and northwest Pacific
(Choi, 1997, 1998; see below).
Marine Magnetic Anomalies
_Powerful support for seafloor spreading is said to be provided
by marine magnetic anomalies -- approximately parallel stripes
of alternating high and low magnetic intensity that characterize
much of the world's midocean ridges.
_According to the Morley-Vine-Matthews hypothesis, first
proposed in 1963, as the fluid basalt welling up along the
midocean ridges spreads horizontally and cools, it is magnetized
by the earth's magnetic field.
_Bands of high intensity are believed to have formed during
periods of normal magnetic polarity, and bands of low intensity
during periods of reversed polarity.
_They are therefore regarded as time lines or isochrons.
_As plate tectonics became accepted, attempts to test this
hypothesis or to find alternative hypotheses ceased.
_Correlations have been made between linear magnetic anomalies
on either side of a ridge, in different parts of the oceans, and
with radiometrically-dated magnetic events on land.
_The results have been used to produce maps showing how the age
of the ocean floor increases steadily with increasing distance
from the ridge axis (McGeary and Plummer, 1998, Fig. 4.19).
_As shown above, this simple picture can be sustained only by
dismissing the possibility of older sediments beneath the basalt
"basement" and by ignoring numerous "anomalously" old rock ages.
_The claimed correlations have been largely qualitative and
subjective, and are therefore highly suspect; virtually no
effort has been made to test them quantitatively by transforming
them to the pole (i.e. recalculating each magnetic profile to a
common latitude).
_In one instance where transformation to the pole was carried
out, the plate-tectonic interpretation of the magnetic anomalies
in the Bay of Biscay was seriously undermined (Storetvedt,
1997).
_Agocs, Meyerhoff, and Kis (1992) applied the same technique in
their detailed, quantitative study of the magnetic anomalies of
the Reykjanes Ridge near Iceland, and found that the
correlations were very poor; the correlation coefficient along
strike averaged 0.31 and that across the ridge 0.17, with limits
of +1 to -1.
_Linear anomalies are known from only 70% of the seismically
active midocean ridges.
_Moreover, the diagrams of symmetrical, parallel, linear bands
of anomalies displayed in many plate-tectonics publications bear
little resemblance to reality (Meyerhoff and Meyerhoff, 1974b;
Beloussov, 1970).
_The anomalies are symmetrical to the ridge axis in less than
50% of the ridge system where they are present, and in about 21%
of it they are oblique to the trend of the ridge.
_In some areas, linear anomalies are present where a ridge
system is completely absent.
_Magnetic measurements by instruments towed near the sea bottom
have indicated that magnetic bands actually consist of many
isolated ovals that may be joined together in different ways.
_The initial, highly simplistic seafloor-spreading model for the
origin of magnetic anomalies has been disproven by ocean
drilling (Pratsch, 1986; Hall and Robinson, 1979).
_First, the hypothesis that the anomalies are produced in the
upper 500 meters of oceanic crust has had to be abandoned.
_Magnetic intensities, general polarization directions, and
often the existence of different polarity zones at different
depths suggest that the source for oceanic magnetic anomalies
lies in deeper levels of oceanic crust not yet drilled (or
dated).
_Second, the vertically alternating layers of opposing magnetic
polarization directions disprove the theory that the oceanic
crust was magnetized entirely as it spread laterally from the
magmatic center, and strongly indicate that oceanic crustal
sequences represent longer geologic times than is now believed.
_A more likely explanation of marine magnetic anomalies is that
they are caused by fault-related bands of rock of different
magnetic properties and have nothing to do with seafloor
spreading (Morris et al., 1990; Choi, Vasil'yev, and Tuezov,
1990; Pratsch, 1986; Grant, 1980).
_The fact that not all the charted magnetic anomalies are formed
of oceanic crustal materials further undermines the
plate-tectonic explanation.
_In the Labrador Sea some anomalies occur in an area of
continental crust that had previously been defined as oceanic
(Grant, 1980).
_In the northwestern Pacific some magnetic anomalies are
likewise located within an area of continental crust -- a
submerged paleoland (Choi, Vasil'yev, and Tuezov, 1990; Choi,
Vasil'yev, and Bhat, 1992).
_Magnetic-anomaly bands strike into the continents in at least
15 places and "dive" beneath Proterozoic or younger rocks.
_Furthermore, they are approximately concentric with respect to
Archean continental shields (Meyerhoff and Meyerhoff, 1972,
1974b).
_These facts imply that instead of being a "taped record" of
seafloor spreading and geomagnetic field reversals during the
past 200 million years, most oceanic magnetic anomalies are the
sites of ancient fractures, which partly formed during the
Proterozoic and have been rejuvenated since.
_The evidence also suggests that Archean continental nuclei have
held approximately the same positions with respect to one
another since their formation -- which is utterly at variance
with continental drift.
Subduction
_Benioff zones are distinct earthquake zones that begin at an
ocean trench and slope landward and downward into the earth.
_In plate tectonics, these deep-rooted fault zones are
interpreted as "subduction zones" where plates descend into the
mantle.
_They are generally depicted as 100-km-thick slabs descending
into the earth either at a constant angle, or at a shallow angle
near the earth's surface and gradually curving around to an
angle of between 60° and 75°.
_Neither representation is correct.
_Benioff zones often consist of two separate sections: an upper
zone with an average dip of 33° extending to a depth of 70-400
km, and a lower zone with an average dip of 60° extending to a
depth of up to 700 km (Benioff, 1954; Isacks and Barazangi,
1977).
_The upper and lower segments are sometimes offset by 100-200
km, and in one case by 350 km (Benioff, 1954, Smoot, 1997a).
_Furthermore, deep earthquakes are disconnected from shallow
ones; very few intermediate earthquakes exist (Smoot, 1997a).
_Many studies have found transverse as well as vertical
discontinuities and segmentation in Benioff zones (e.g. Carr,
Stoiber, and Drake, 1973; Swift and Carr, 1974; Teisseyre et
al., 1974; Carr, 1976; Spence, 1977; Ranneft, 1979).
_The evidence therefore does not favor the notion of a
continuous, downgoing slab.
_Plate tectonicists insist that the volume of crust generated at
midocean ridges is equaled by the volume subducted.
_But whereas 80,000 km of midocean ridges are supposedly
producing new crust, only 30,500 km of trenches exist.
_Even if we add the 9000 km of "collision zones," the figure is
still only half that of the "spreading centers" (Smoot, 1997a).
_With two minor exceptions (the Scotia and Lesser Antilles
trench/arc systems), Benioff zones are absent from the margins
of the Atlantic, Indian, Arctic, and Southern Oceans.
_Many geological facts demonstrate that subduction is not taking
place in the Lesser Antilles arc; if it were, the continental
Barbados Ridge should now be 200-400 km beneath the Lesser
Antilles (Meyerhoff and Meyerhoff, 1974a).
_Kiskyras (1990) presented geological, volcanological,
petrochemical, and seismological data contradicting the belief
that the African plate is being subducted under the Aegean Sea.
_Africa is allegedly being converged on by plates spreading from
the east, south, and west, yet it exhibits no evidence
whatsoever for the existence of subduction zones or orogenic
belts.
_Antarctica, too, is almost entirely surrounded by alleged
"spreading" ridges without any corresponding subduction zones,
but fails to show any signs of being crushed.
_It has been suggested that Africa and Antarctica may remain
stationary while the surrounding ridge system migrates away from
them, but this would require the ridge marking the "plate
boundary" between Africa and Antarctica to move in opposite
directions simultaneously (Storetvedt, 1997)!
_If up to 13,000 kilometers of lithosphere had really been
subducted in circum-Pacific deep-sea trenches, vast amounts of
oceanic sediments should have been scraped off the ocean floor
and piled up against the landward margin of the trenches.
_However, sediments in the trenches are generally not present in
the volumes required, nor do they display the expected degree of
deformation (Storetvedt, 1997; Choi, 1999b; Gnibidenko, Krasny,
and Popov, 1978; Suzuki et al., 1997).
_Scholl and Marlow (1974), who support plate tectonics, admitted
to being "genuinely perplexed as to why evidence for subduction
or offscraping of trench deposits is not glaringly apparent" (p.
268).
_Plate tectonicists have had to resort to the highly dubious
notion that unconsolidated deep-ocean sediments can slide
smoothly into a Benioff zone without leaving any significant
trace.
_Moreover, fore-arc sediments, where they have been analyzed,
have generally been found to be derived from the volcanic arc
and the adjacent continental block, not from the oceanic region
(Pratsch, 1990; Wezel, 1986).
_The very low level of seismicity, the lack of a megathrust, and
the existence of flat-lying sediments at the base of oceanic
trenches contradict the alleged presence of a downgoing slab
(Dickins and Choi, 1998).
_Attempts by Murdock (1997), who accepts many elements of plate
tectonics, to publicize the lack of a megathrust in the Aleutian
trench (i.e. a million or more meters of displacement of the
Pacific plate as it supposedly underthrusts the North American
plate) have met with vigorous resistance and suppression by the
plate-tectonics establishment.
_Subduction along Pacific trenches is also refuted by the fact
that the Benioff zone often lies 80 to 150 km landward from the
trench; by the evidence that Precambrian continental structures
continue into the ocean floor; and by the evidence for submerged
continental crust under the northwestern and southeastern
Pacific, where there are now deep abyssal plains and trenches
(Choi, 1987, 1998, 1999c; Smoot 1998b; Tuezov, 1998).
_If the "Pacific plate" is colliding with and diving under the
"North American plate", there should be a stress buildup along
the San Andreas Fault.
_The deep Cajon Pass drillhole was intended to confirm this but
showed instead that no such stress is present (C. W. Hunt,
1992).
_In the active island-arc complexes of southeast Asia, the arcs
bend back on themselves, forming hairpin-like shapes that
sometimes involve full 180° changes in direction.
_This also applies to the postulated subduction zone around
India.
_How plate collisions could produce such a geometry remains a
mystery (Meyerhoff, 1995; H. A. Meyerhoff and Meyerhoff, 1977).
_Rather than being continuous curves, trenches tend to consist
of a row of straight segments, which sometimes differ in depth
by more than 4 km.
_Aseismic buoyant features (e.g. seamounts), which are
frequently found at the juncture of these segments, are
connected with increased deep-earthquake and volcanic activity
on the landward side of the trench, whereas theoretically their
"arrival" at a subduction zone should reduce or halt such
activity (Smoot, 1997a).
_Plate tectonicists admit that it is hard to see how the
subduction of a cold slab could result in the high heat flow or
arc volcanism in back-arc regions or how plate convergence could
give rise to back-arc spreading (Uyeda, 1986).
_Evidence suggests that oceanic, continental, and back-arc rifts
are actually tensional structures developed to relieve stress in
a strong compressional stress system, and therefore have nothing
to do with seafloor spreading (Dickins, 1997).
_An alternative view of Benioff zones is that they are very
ancient contraction fractures produced by the cooling of the
earth (Meyerhoff et al., 1992b, 1996a).
_The fact that the upper part of the Benioff zones usually dips
at less than 45° and the lower part at more than 45° suggests
that the lithosphere is under compression and the lower mantle
under tension.
_Furthermore, since a contracting sphere fractures along great
circles (Bucher, 1956), this would account for the fact that
both the circum-Pacific seismotectonic belt and the
Alpine-Himalayan (Tethyan) belt lie on approximate circles.
_Finally, instead of oceanic crust being absorbed beneath the
continents along ocean trenches, continents may actually be
overriding adjacent oceanic areas to a limited extent, as is
indicated by the historical geology of China, Indonesia, and the
western Americas (Storetvedt, 1997; Pratsch, 1986; Krebs, 1975).
Uplift and Subsidence
Vertical Tectonics
_Classical plate tectonics seeks to explain all geologic
structures primarily in terms of simple lateral movements of
lithospheric plates -- their rifting, extension, collision, and
subduction.
_But random plate interactions are unable to explain the
periodic character of geological processes, i.e. the geotectonic
cycle, which sometimes operates on a global scale (Wezel, 1992).
_Nor can they explain the large-scale uplifts and subsidences
that have characterized the evolution of the earth's crust,
especially those occurring far from "plate boundaries" such as
in continental interiors, and vertical oscillatory motions
involving vast regions (Ilich, 1972; Beloussov, 1980, 1990;
Chekunov, Gordienko, and Guterman, 1990; Genshaft and
Saltykowski, 1990).
_The presence of marine strata thousands of meters above sea
level (e.g. near the summit of Mount Everest) and the great
thicknesses of shallow-water sediment in some old basins
indicate that vertical crustal movements of at least 9 km above
sea level and 10-15 km below sea level have taken place
(Spencer, 1977).
_Major vertical movements have also taken place along
continental margins.
_For example, the Atlantic continental margin of North America
has subsided by up to 12 km since the Jurassic (Sheridan, 1974).
_In Barbados, Tertiary coals representing a shallow-water,
tropical environment occur beneath deep-sea oozes, indicating
that during the last 12 million years, the crust sank to over
4-5 km depth for the deposition of the ooze and was then raised
again.
_A similar situation occurs in Indonesia, where deep-sea oozes
occur above sea level, sandwiched between shallow-water Tertiary
sediments (James, 1994).
_The primary mountain-building mechanism in plate tectonics is
lateral compression caused by collisions -- of continents,
island arcs, oceanic plateaus, seamounts, and ridges.
_In this model, subduction proceeds without mountain building
until collision occurs, whereas in the noncollision model
subduction alone is supposed to cause mountain building.
_As well as being mutually contradictory, both models are
inadequate, as several supporters of plate tectonics have
pointed out (e.g. Cebull and Shurbet, 1990, 1992; Van Andel,
1998).
_The noncollision model fails to explain how continuous
subduction can give rise to discontinuous orogeny, while the
collision model is challenged by occurrences of mountain
building where no continental collision can be assumed, and it
fails to explain contemporary mountain-building activity along
such chains as the Andes and around much of the rest of the
Pacific rim.
_Asia supposedly collided with Europe in the late Paleozoic,
producing the Ural mountains, but abundant geological field data
demonstrate that the Siberian and East European (Russian)
platforms have formed a single continent since Precambrian times
(Meyerhoff and Meyerhoff, 1974a).
_McGeary and Plummer (1998) state that the plate-tectonic
reconstruction of the formation of the Appalachians in terms of
three successive collisions of North America seems "too
implausible even for a science fiction plot" (p. 114), but add
that an understanding of plate tectonics makes the theory more
palatable.
_Ollier (1990), on the other hand, states that fanciful
plate-tectonic explanations ignore all the geomorphology and
much of the known geological history of the Appalachians.
_He also says that of all the possible mechanisms that might
account for the Alps, the collision of the African and European
plates is the most naive.
_The Himalayas and the Tibetan Plateau were supposedly uplifted
by the collision of the Indian plate with the Asian plate.
_However, this fails to explain why the beds on either side of
the supposed collision zone remain comparatively undisturbed and
low-dipping, whereas the Himalayas have been uplifted,
supposedly as a consequence, some 100 km away, along with the
Kunlun mountains to the north of the Tibetan Plateau.
_River terraces in various parts of the Himalayas are almost
perfectly horizontal and untilted, suggesting that the Himalayas
were uplifted vertically, rather than as the result of
horizontal compression (Ahmad, 1990).
_Collision models generally assume that the uplift of the
Tibetan Plateau began during or after the early Eocene (post-50
million years), but paleontological, paleoclimatological,
paleoecological, and sedimentological data conclusively show
that major uplift could not have occurred before earliest
Pliocene time (5 million years ago) (Meyerhoff, 1995).
_There is ample evidence that mantle heat flow and material
transport can cause significant changes in crustal thickness,
composition, and density, resulting in substantial uplifts and
subsidences.
_This is emphasized in many of the alternative hypotheses to
plate tectonics (for an overview, see Yano and Suzuki, 1999),
such as the model of endogenous regimes (Beloussov, 1980, 1981,
1990, 1992; Pavlenkova, 1995, 1998).
_Plate tectonicists, too, increasingly invoke mantle diapirism
as a mechanism for generating or promoting tectogenesis; there
is now abundant evidence that shallow magma chambers are
ubiquitous beneath active tectonic belts.
_The popular hypothesis that crustal stretching was the main
cause of the formation of deep sedimentary basins on continental
crust has been contradicted by numerous studies; mantle
upwelling processes and lithospheric density increases are
increasingly being recognized as an alternative mechanism
(Pavlenkova, 1998; Artyushkov 1992; Artyushkov and Baer, 1983;
Anfiloff, 1992; Zorin and Lepina, 1989).
_This may involve gabbro-eclogite phase transformations in the
lower crust (Artyushkov 1992; Haxby, Turcotte, and Bird, 1976;
Joyner, 1967), a process that has also been proposed as a
possible explanation for the continuing subsidence of the North
Sea Basin, where there is likewise no evidence of large-scale
stretching (Collette, 1968).
_Plate tectonics predicts simple heat-flow patterns around the
earth.
_There should be a broad band of high heat flow beneath the full
length of the midocean rift system, and parallel bands of high
and low heat flow along the Benioff zones.
_Intraplate regions are predicted to have low heat flow.
_The pattern actually observed is quite different.
_There are criss-crossing bands of high heat flow covering the
entire surface of the earth (Meyerhoff et al., 1996a).
_Intra-plate volcanism is usually attributed to "mantle plumes"
-- upwellings of hot material from deep in the mantle,
presumably the core-mantle boundary.
_The movement of plates over the plumes is said to give rise to
hotspot trails (chains of volcanic islands and seamounts).
_Such trails should therefore show an age progression from one
end to the other, but a large majority show little or no age
progression (Keith, 1993; Baksi, 1999).
_On the basis of geological, geochemical, and geophysical
evidence, Sheth (1999) argued that the plume hypothesis is
ill-founded, artificial, and invalid, and has led earth
scientists up a blind alley.
_Active tectonic belts are located in bands of high heat flow,
which are also characterized by several other phenomena that do
not readily fit in with the plate-tectonics hypothesis.
_These include: bands of microearthquakes (including "diffuse
plate boundaries") that do not coincide with plate-tectonic
predicted locations; segmented belts of linear faults,
fractures, and fissures; segmented belts of mantle upwellings
and diapirs; vortical geological structures; linear lenses of
anomalous (low-velocity) upper mantle that are commonly overlain
by shallower, smaller low-velocity zones; the existence of
bisymmetrical deformation in all foldbelts, with coexisting
states of compression and tension; strike-slip zones and similar
tectonic lines ranging from simple rifts to Verschluckungszonen
("engulfment zones"); eastward-shifting tectonic-magmatic belts;
and geothermal zones.
_Investigation of these phenomena has led to the development of
a major new hypothesis of geodynamics, known as surge tectonics,
which rejects both seafloor spreading and continental drift
(Meyerhoff et al., 1992b, 1996a; Meyerhoff, 1995).
_Surge tectonics postulates that all the major features of the
earth's surface, including rifts, foldbelts, metamorphic belts,
and strike-slip zones, are underlain by shallow (less than 80
km) magma chambers and channels (known as "surge channels").
_Seismotomographic data suggest that surge channels form an
interconnected worldwide network, which has been dubbed "the
earth's cardiovascular system."
_Surge channels coincide with the lenses of anomalous mantle and
associated low-velocity zones referred to above, and active
channels are also characterized by high heat flow and
microseismicity.
_Magma from the asthenosphere flows slowly through active
channels at the rate of a few centimeters a year.
_Horizontal flow is demonstrated by two major surface features:
linear, belt-parallel faults, fractures, and fissures; and the
division of tectonic belts into fairly uniform segments.
_The same features characterize all lava flows and tunnels, and
have also been observed on Mars, Venus, and several moons of the
outer planets.
_Surge tectonics postulates that the main cause of geodynamics
is lithosphere compression, generated by the cooling and
contraction of the earth.
_As compression increases during a geotectonic cycle, it causes
the magma to move through a channel in pulsed surges and
eventually to rupture it, so that the contents of the channel
surge bilaterally upward and outward to initiate tectogenesis.
_The asthenosphere (in regions where it is present) alternately
contracts during periods of tectonic activity and expands during
periods of tectonic quiescence.
_The earth's rotation, combined with differential lag between
the more rigid lithosphere above and the more fluid
asthenosphere below, causes the fluid or semifluid materials to
move predominantly eastward.
_This explains the eastward migration through time of many
magmatic or volcanic arcs, batholiths, rifts, depocenters, and
foldbelts.
The Continents
_It is a striking fact that nearly all the sedimentary rocks
composing the continents were laid down under the sea.
_The continents have suffered repeated marine inundations, but
because sediments were mostly deposited in shallow water (less
than 250 m), the seas are described as "epicontinental."
_Marine transgressions and regressions are usually attributed
mainly to eustatic changes of sea level caused by alterations in
the volume of midocean ridges.
_Van Andel (1994) points out that this explanation cannot
account for the 100 or so briefer cycles of sea-level changes,
especially since transgressions and regressions are not always
simultaneous all over the globe.
_He proposes that large regions or whole continents must undergo
slow vertical, epeirogenic movements, which he attributes to an
uneven distribution of temperature and density in the mantle,
combined with convective flow.
_Some workers have linked marine inundations and withdrawals to
a global thermal cycle, bringing about continental uplift and
subsidence (Rutland, 1982; Sloss and Speed, 1974).
_Van Andel (1994) admits that epeirogenic movements "fit poorly
into plate tectonics" (p. 170), and are therefore largely
ignored.
_Van Andel (1994) asserts that "plates" rise or fall by no more
than a few hundred meters -- this being the maximum depth of
most "epicontinental" seas.
_However, this overlooks an elementary fact: huge thicknesses of
sediments were often deposited during marine incursions, often
requiring vertical crustal movements of many kilometers.
_Sediments accumulate in regions of subsidence, and their
thickness is usually close to the degree of downwarping.
_In the unstable, mobile belts bordering stable continental
platforms, many geosynclinal troughs and circular depressions
have accumulated sedimentary thicknesses of 10 to 14 km, and in
some cases of 20 km.
_Although the sedimentary cover on the platforms themselves is
often less than 1.5 km thick, basins with sedimentary
thicknesses of 10 km and even 20 km are not unknown (C. B. Hunt,
1992; Dillon, 1974; Beloussov, 1981; Pavlenkova, 1998).
_Subsidence cannot be attributed solely to the weight of the
accumulating sediments because the density of sedimentary rocks
is much lower than that of the subcrustal material; for
instance, the deposition of 1 km of marine sediment will cause
only half a kilometer or so of subsidence (Holmes, 1965;
Jeffreys, 1976).
_Moreover, sedimentary basins require not only continual
depression of the base of the basin to accommodate more
sediments, but also continuous uplift of adjacent land to
provide a source for the sediments.
_In geosynclines, subsidence has commonly been followed by
uplift and folding to produce mountain ranges, and this can
obviously not be accounted for by changes in surface loading.
_The complex history of the oscillating uplift and subsidence of
the crust appears to require deep-seated changes in lithospheric
composition and density, and vertical and horizontal movements
of mantle material.
_That density is not the only factor involved is shown by the
fact that in regions of tectonic activity vertical movements
often intensify gravity anomalies rather than acting to restore
isostatic equilibrium.
_For example, the Greater Caucasus is overloaded, yet it is
rising rather than subsiding (Beloussov, 1980; Jeffreys, 1976).
_In regions where all the sediments were laid down in shallow
water, subsidence must somehow have kept pace with
sedimentation.
_In eugeosynclines, on the other hand, subsidence proceeded
faster than sedimentation, resulting in a marine basin several
kilometers deep.
_Examples of eugeosynclines prior to the uplift stage are the
Sayans in the Early Paleozoic, the eastern slope of the Urals in
the Early and Middle Paleozoic, the Alps in the Jurassic and
Early Cretaceous, and the Sierra Nevada in the Triassic
(Beloussov, 1980).
_Plate tectonicists often claim that geosynclines are formed
solely at plate margins at the boundaries between continents and
oceans.
_However, there are many examples of geosynclines having formed
in intracontinental settings (Holmes, 1965), and the belief that
the ophiolites found in certain geosynclinal areas are
invariably remnants of oceanic crust is contradicted by a large
volume of evidence (Beloussov, 1981; Bhat, 1987; Luts, 1990;
Sheth, 1997).
The Oceans
_In the past, sialic clastic material has been transported to
today's continents from the direction of the present-day oceans,
where there must have been considerable areas of land that
underwent erosion (Dickins, Choi, and Yeates, 1992; Beloussov,
1962).
_For instance, the Paleozoic geosyncline along the seaboard of
eastern North America, an area now occupied by the Appalachian
mountains, was fed by sialic clasts from a borderland
("Appalachia") in the adjacent Atlantic.
_Other submerged borderlands include the North Atlantic
Continent or Scandia (west of Spitsbergen and Scotland),
Cascadia (west of the Sierra Nevada), and Melanesia (southeast
of Asia and east of Australia) (Umbgrove, 1947; Gilluly, 1955;
Holmes, 1965).
_A million cubic kilometers of Devonian micaceous sediments from
Bolivia to Argentina imply an extensive continental source to
the west where there is now the deep Pacific Ocean (Carey,
1994).
_During Paleozoic-Mesozoic-Paleogene times, the Japanese
geosyncline was supplied with sediments from land areas in the
Pacific (Choi, 1984, 1987).
_When trying to explain sediment sources, plate tectonicists
sometimes argue that sediments were derived from the existing
continents during periods when they were supposedly closer
together (Bahlburg, 1993; Dickins, 1994a; Holmes, 1965).
_Where necessary, they postulate small former land areas
(microcontinents or island arcs), which have since been either
subducted or accreted against continental margins as "exotic
terranes" (Nur and Ben-Avraham, 1982; Kumon et al., 1988; Choi,
1984).
_However, mounting evidence is being uncovered that favors the
foundering of sizable continental landmasses, whose remnants are
still present under the ocean floor (see below).
_Oceanic crust is regarded as much thinner and denser than
continental crust: the crust beneath oceans is said to average
about 7 km thick and to be composed largely of basalt and
gabbro, whereas continental crust averages about 35 km thick and
consists chiefly of granitic rock capped by sedimentary rocks.
_However, ancient continental rocks and crustal types
intermediate between standard "continental" and "oceanic" crust
are increasingly being discovered in the oceans (Sanchez Cela,
1999), and this is a serious embarrassment for plate tectonics.
_The traditional picture of the crust beneath oceans being
universally thin and graniteless may well be further undermined
in the future, as oceanic drilling and seismic research
continue.
_One difficulty is to distinguish the boundary between the lower
oceanic crust and upper mantle in areas where high- and
low-velocity layers alternate (Orlenok, 1986; Choi, Vasil'yev,
and Bhat, 1992).
_For example, the crust under the Kuril deep-sea basin is 8 km
thick if the 7.9 km/s velocity layer is taken as the
crust-mantle boundary (Moho), but 20-30 km thick if the 8.2 or
8.4 km/s layer is taken as the Moho (Tuezov, 1998).
_Small ocean basins cover an area equal to about 5% of that of
the continents, and are characterized by transitional types of
crust (Menard, 1967).
_This applies to the Caribbean Sea, the Gulf of Mexico, the
Japan Sea, the Okhotsk Sea, the Black Sea, the Caspian Sea, the
Mediterranean, the Labrador Sea and Baffin Bay, and the marginal
(back-arc) basins along the western side of the Pacific
(Beloussov and Ruditch, 1961; Ross, 1974; Sheridan, 1974; Choi,
1984; Grant, 1992).
_In plate tectonics, the origin of marginal basins, with their
complex crustal structure, has remained an enigma, and there is
no basis for the assumption that some kind of seafloor spreading
must be involved; rather, they appear to have originated by
vertical tectonics (Storetvedt, 1997; Wezel, 1986).
_Some plate tectonicists have tried to explain the transitional
crust of the Caribbean in terms of the continentalization of a
former deep ocean area, thereby ignoring the stratigraphic
evidence that the Caribbean was a land area in the Early
Mesozoic (Van Bemmelen, 1972).
_There are over 100 submarine plateaus and aseismic ridges
scattered throughout the oceans, many of which were once
subaerially exposed (Nur and Ben-Avraham, 1982; Dickins, Choi,
and Yeates, 1992; Storetvedt, 1997).
_They make up about 10% of the ocean floor.
_Many appear to be composed of modified continental crust 20-40
km thick -- far thicker than "normal" oceanic crust.
_They often have an upper 10-15 km crust with compressional-wave
velocities typical of granitic rocks in continental crust.
_They have remained obstacles to predrift continental fits, and
have therefore been interpreted as extinct spreading ridges,
anomalously thickened oceanic crust, or subsided continental
fragments carried along by the "migrating" seafloor.
_If seafloor spreading is rejected, they cease to be anomalous
and can be interpreted as submerged, in-situ continental
fragments that have not been completely "oceanized."
_Shallow-water deposits ranging in age from mid-Jurassic to
Miocene, as well as igneous rocks showing evidence of subaerial
weathering, were found in 149 of the first 493 boreholes drilled
in the Atlantic, Indian, and Pacific Oceans.
_These shallow-water deposits are now found at depths ranging
from 1 to 7 km, demonstrating that many parts of the present
ocean floor were once shallow seas, shallow marshes, or land
areas (Orlenok, 1986; Timofeyev and Kholodov, 1984).
_From a study of 402 oceanic boreholes in which shallow-water or
relatively shallow-water sediments were found, Ruditch (1990)
concluded that there is no systematic correlation between the
age of shallow-water accumulations and their distance from the
axes of the midoceanic ridges, thereby disproving the
seafloor-spreading model.
_Some areas of the oceans appear to have undergone continuous
subsidence, whereas others experienced alternating episodes of
subsidence and elevation.
_The Pacific Ocean appears to have formed mainly from the Late
Jurassic to the Miocene, the Atlantic Ocean from the Late
Cretaceous to the end of the Eocene, and the Indian Ocean during
the Paleocene and Eocene.
_In the North Atlantic and Arctic Oceans, modified continental
crust (mostly 10-20 km thick) underlies not only ridges and
plateaus but most of the ocean floor; only in deep-water
depressions is typical oceanic crust found.
_Since deep-sea drilling has shown that large areas of the North
Atlantic were previously covered with shallow seas, it is
possible that much of the North Atlantic was continental crust
before its rapid subsidence (Pavlenkova, 1995, 1998; Sanchez
Cela, 1999).
_Lower Paleozoic continental rocks with trilobite fossils have
been dredged from seamounts scattered over a large area
northeast of the Azores.
_Furon (1949) concluded that the continental cobbles had not
been carried there by icebergs and that the area concerned was a
submerged continental zone.
_Bald Mountain, from which a variety of ancient continental
material has been dredged, could certainly be a foundered
continental fragment.
_In the equatorial Atlantic, shallow-water and continental rocks
are ubiquitous (Timofeyev et al., 1992; Udintsev, 1996).
_There is evidence that the midocean ridge system was shallow or
partially emergent in Cretaceous to Early Tertiary time.
_For instance, in the Atlantic subaerial deposits have been
found on the North Brazilian Ridge (Bader et al., 1971), near
the Romanche and Vema fracture zones adjacent to equatorial
sectors of the Mid-Atlantic Ridge (Bonatti and Chermak, 1981;
Bonatti and Honnorez, 1971), on the crest of the Reykjanes
Ridge, and in the Faeroe-Shetland region (Keith, 1993).
_Oceanographic and geological data suggest that a large part of
the Indian Ocean, especially the eastern part, was land
("Lemuria") from the Jurassic until the Miocene.
_The evidence includes seismic and palynological data and
subaerial weathering which suggest that the Broken and Ninety
East Ridges were part of an extensive, now sunken landmass;
extensive drilling, seismic, magnetic, and gravity data pointing
to the existence an Alpine-Himalayan foldbelt in the
northwestern Indian Ocean, associated with a foundered
continental basement; data that continental basement underlies
the Scott, Exmouth, and Naturaliste plateaus west of Australia;
and thick Triassic and Jurassic sedimentation on the western and
northwestern shelves of the Australian continent which shows
progradation and current direction indicating a western source
(Dickins, 1994a; Udintsev, Illarionov, and Kalinin, 1990;
Udintsev and Koreneva, 1982; Wezel, 1988).
_Geological, geophysical, and dredging data provide strong
evidence for the presence of Precambrian and younger continental
crust under the deep abyssal plains of the present northwest
Pacific (Choi, Vasil'yev, and Tuezov, 1990; Choi, Vasil'yev, and
Bhat, 1992).
_Most of this region was either subaerially exposed or very
shallow sea during the Paleozoic to Early Mesozoic, and first
became deep sea about the end of the Jurassic.
_Paleolands apparently existed on both sides of the Japanese
islands.
_They were largely emergent during the
Paleozoic-Mesozoic-Paleogene, but were totally submerged during
Paleogene to Miocene times.
_Those on the Pacific side included the great Oyashio paleoland
and the Kuroshio paleoland.
_The latter, which was as large as the present Japanese islands
and occupied the present Nankai Trough area, subsided in the
Miocene, at the same time as the upheaval of the Shimanto
geosyncline, to which it had supplied vast amounts of sediments
(Choi, 1984, 1987; Harata et al., 1978; Kumon et al., 1988).
_There is also evidence of paleolands in the southwest Pacific
around Australia (Choi, 1997) and in the southeast Pacific
during the Paleozoic and Mesozoic (Choi, 1998; Isaacson, 1975;
Bahlburg, 1993; Isaacson and Martinez, 1995).
_After surveying the extensive evidence for former continental
land areas in the present oceans, Dickins, Choi, and Yeates
(1992) concluded:
_We are surprised and concerned for the objectivity and honesty
of science that such data can be overlooked or ignored. ...
_There is a vast need for future Ocean Drilling Program
initiatives to drill below the base of the basaltic ocean floor
crust to confirm the real composition of what is currently
designated oceanic crust.
_(p. 198)
Conclusion
_Plate tectonics -- the reigning paradigm in the earth sciences
-- faces some very severe and apparently fatal problems.
_Far from being a simple, elegant, all-embracing global theory,
it is confronted with a multitude of observational anomalies,
and has had to be patched up with a complex variety of ad-hoc
modifications and auxiliary hypotheses.
_The existence of deep continental roots and the absence of a
continuous, global asthenosphere to "lubricate" plate motions,
have rendered the classical model of plate movements untenable.
_There is no consensus on the thickness of the "plates" and no
certainty as to the forces responsible for their supposed
movement.
_The hypotheses of large-scale continental movements, seafloor
spreading and subduction, and the relative youth of the oceanic
crust are contradicted by a substantial volume of data.
_Evidence for significant amounts of submerged continental crust
in the present-day oceans provides another major challenge to
plate tectonics.
_The fundamental principles of plate tectonics therefore require
critical reexamination, revision, or rejection.
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