Some problems with Plate Tectonics

Reassembling the Continental Jigsaw Puzzle:
One of the factors that first excited attention to the possibility of continental drift, and the rifting apart of early super-continents to form the present disposition of land masses, was the remarkably close fit that appears to exist between the shapes of the eastern seaboard of the Americas and the western coastline of Africa and Europe. Sophisticated topological fits have been proposed, vast numbers of papers written and conferences have been dedicated to the task of perfecting the levels of fit achieved by these models. Sceptics have on the other hand questioned many aspects of these fits (Voisey, 1958; Pratt, 2000). To highlight the creativity involved with some of these reconstructions, it has been pointed-out that if the sub-continent of Australia were to be translated across the southern Pacific propelled round Cape Horn, moved up the full length of the Atlantic, and rotated through 180^o, then a good fit would be achieved between the east coast of Australia and the east coast of North America (Pratt, 2000). There are it seems even remarkable similarities between the geological and palaeontological features of these two regions (Pratt, 2000). More seriously, it would seem that although there is strong geological evidence for plate movements of up to a few hundred kilometres there is little to support the notion that the crustal plates have moved upwards of 9000 km as required by PT. There are it appears also rather too many inconsistencies in the various fits for this evidence to be taken as definitive proof of PT. As highlighted by Pratt (2000), there is more than 3.5 million square kilometres that fail to fit in with the Bullard et alia (1965) computer generated emergence of the Americas, Africa and Europe from the super continent of Pangaea. It seems there are similar difficulties arising from the supposed break-up of Gondwanaland in the southern hemisphere, as postulated by Smith and Hallam (1970) and Dietz and Holden (1970), to account for the formation of the southern land masses of the Antarctic, Australia and the errant India. India is supposed to have dislodged itself from Gonwanaland and been propelled on a 9000 km northward journey to collide with the Asian plate with such force as to form the Himalayan mountain range. As pointed out by Pratt (2000) there is “overwhelming geological and palaeontological evidence that India has been an integral part of Asia since pre-Cambrian times”, well before its hypothesised northward journey from Antarctica and Australia with whom it shares very little floral and faunal similarities. Indeed, as Pratt (2000) so eloquently puts it, “the supposed ‘flight of India’ is no more than a flight of fancy”.       

Biogeograhic boundaries based upon floral and faunal distributions that would follow from PT models are often in strong contradiction with those actually existing. Indeed, it would appear that the known palaeontological data on the distribution of fossils is rather more consistent with current distributions of continental land mass than those upon which PT is predicated (Smiley, 1992). In a major global study based upon floral and faunal distributions, Meyerhoff et  alia (1996) concluded that current biogeographical boundaries are seriously out of step with the boundaries that would be anticipated from plate tectonic models. They comment that “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”. It seems that all is not as simple as is often suggested.

Ocean Sediment Age:

A fundamental notion in PT is that of sea-floor spreading. In this process new oceanic crust is created around the oceanic ridges, or “spreading zones”, where molten material from the earth’s interior is extruded up into fissures caused by the tearing apart of the plates. This new crust is characterised as gradually moving across the ocean floor, like a “conveyor belt”, until it comes into contact with the relatively thicker continental crust. At these collision zones the relatively thinner oceanic crust is said to be forced down into trenches, “subduction zones”, where the newer oceanic crust is lost back into the molten interior. If these notions are correct then one would anticipate the lowest sedimentary layers deposited upon this new ocean crust to increase in age the further one moves away from the spreading zone. Very extensive deep sea drilling programmes have been undertaken to test this hypothesis, with seemingly great success. It was found in a NSF study (1969-73) that the ages of sediments immediately overlying the first basalt rock, supposed to be the new ocean crust being forced out from the spreading zone, do indeed display a gradual increase in age as the distance from the spreading zone increases.

Once again, however, there appear to be grounds for supposing that the evidence on sea-floor geology has been chosen selectively to support the hypotheses of PT. Smoot et al (1995) have demonstrated that most of the published charts showing the ocean floors have been drafted using the data that supports the ideas of PT. They suggest that much of the accurate information currently available has been ignored because it is at odds with the notions of PT. For example, they show that from side-scanning radar images there is evidence that the mid-oceanic ridges are cut with thousands of long and straight, ridge parallel, fissures and fractures that have older crustal rock between them. There are also numerous areas in all the oceans of the world where seabed rock, of continental origin and up to 3.74ba in age, are located where PT would suggest the rock should be of an age at least 2 orders of magnitude younger (Timofeyev, 1992; Udintsev, 1996). Dickins et alia (1992) undertook a detailed survey of the evidence relating to the existence of large continental crust within the present oceans, and concluded that “we are surprised and concerned for the objectivity of science that such data should be overlooked or ignored”. There are also strong and well founded suspicions that had the deep sea drilling boreholes been able to penetrate through the first layers of basalt, older sedimentary layers would be found to overlay possibly even older horizontal layers of basalt. On the basis of the above cited survey, Dickins et alia (1992) opined that “there is a vast need for future Ocean Drilling Program initiatives to drill below the base of the basaltic floor crust to confirm the real composition of what is currently designated oceanic crust”. As will be argued later there are other possibly more convincing models for how these finds on sedimentary age could be explained.

Magnetic Anomaly Evidence:

It has been claimed that stripes of newly formed oceanic crust roughly parallel to the spreading zones, display reversals in magnetic polarity that are reasonably symmetry about the oceanic ridges (Sullivan, 1991). These magnetic signatures are believed to have been captured when the molten magma being extruded into the spreading zone solidified. For some curious reason these newly created widths of magnetised rock are believed to be split into equal halves and propelled off in opposite directions to create bands of magnetised rock that display symmetry about the spreading zones. It has been pointed out that the evidence of this symmetry and chronology of spreading, supporting PT, is rather less convincing than is sometimes implied. The licourice-allsort appearance of some of the text book summaries of this evidence fails to indicate the many serious anomalies. Magnetic stripes of magma intrusions display very imperfect symmetry, and indeed often occur in sequences that do not represent a linear time-wise evolution (Meyerhoff et al, 1974). The stripes often occur within seabed rock that is very much older and sometimes of continental origins (Grant, 1980; Choi et al, 1992), and furthermore has been shown to display anisotropy with depth. It would appear that here too much of the data is open to alternative explanations.

 Much of the above post has been taken from the paper "On the Causes of Vertical Motions of Lithosphere", James G A Croll, Frontiers meeting, Geological Society of London, November, 2011.