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the Mid-Atlantic Ridge (Original)

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Author Topic: the Mid-Atlantic Ridge (Original)  (Read 9622 times)
Carolyn Silver
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Posts: 4611

« Reply #60 on: July 28, 2008, 11:35:21 pm »

Like the Bullard fit, the Smith & Hallam reconstruction of the Gondwanaland continents tries to fit the continents along the 500-fathom (1-km) depth contour on the continental shelves. 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. Dietz & Holden based their fit on the 2-km depth contour, but they still have 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, and in some places the ocean-continent transition zone is several hundred kilometers wide. 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'.
    The curvature of continental contours is often so similar that many shorelines can be fitted together quite well even though they can never have been in juxtaposition. For instance, eastern Australia fits well with eastern North America, and there are also remarkable geological and paleontological similarities, probably due to the similar tectonic backgrounds of the two regions. The geological resemblances of opposing Atlantic coastlines may be due to the areas having belonged to the same tectonic belt, but the differences -- which are rarely mentioned -- are sufficient to show that the areas were situated in distant parts of the belt. H.P. Blavatsky regarded the similarities in the geological structure, fossils, and marine life of the opposite coasts of the Atlantic in certain periods as evidence that 'there has been, in distant pre-historic ages, a continent which extended from the coast of Venezuela, across the Atlantic Ocean, to the Canarese Islands and North Africa, and from Newfoundland nearly to the coast of France' [4].
    One of the main props of continental drift is paleomagnetism -- the study of the magnetism of ancient rocks and sediments. For each continent a 'polar wander path' can be constructed, and these are interpreted to mean that the continents have moved vast distances over the earth's surface. However, paleomagnetism is very unreliable and frequently produces inconsistent and contradictory results. For instance, paleomagnetic data imply that during the mid-Cretaceous Azerbaijan and Japan were in the same place! When individual paleomagnetic pole positions, rather than averaged curves, are plotted on world maps, the scatter is huge, often wider than the Atlantic.
    One of the basic assumptions of paleomagnetism is that rocks retain the magnetization they acquire at the time they formed. In reality, rock magnetism is subject to modification by later magnetism, weathering, metamorphism, tectonic deformation, and chemical changes. Horizontal and vertical rotations of crustal blocks further complicate the picture. Another questionable assumption is that over long periods of time the geomagnetic field approximates a simple dipole (N-S) field oriented along the earth's rotation axis. If, in the past, 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.
    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. Similarly, 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.
    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. There is, however, overwhelming geological and paleontological evidence that India has been an integral part of Asia since Precambrian time. If the long journey of India had actually happened, 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. It would appear that the supposed 'flight of India' is no more than a flight of fancy!
    It is often claimed that plate-tectonic reassemblies of the continents can help to explain climatic changes and the distribution of plants and animals in the past. However, detailed studies have shown that shifting the continents succeeds at best in explaining local or regional climatic features for a particular period, and invariably fails to explain the global climate for the same period. A.A. Meyerhoff et al. 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. 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.' Before their study was published by the Geological Society of America, a group of earth-science graduates was invited to study the manuscript. They became deeply disturbed by what they read, and commented: 'If this global study of biodiversity through time is correct, and it is very convincingly presented, then a lot of what we are being taught about plate tectonics should more aptly be called "Globaloney" ' [5].
    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 [6]. The known distributions of fossil organisms are more consistent with an earth model like that of today than with continental-drift models. 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. A few drifters have recognized the need for intermittent land bridges after the supposed separation of the continents. 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. There is growing evidence that these land bridges formed part of larger former landmasses in the present oceans (see below).
    The present distribution of land and water is characterized by a number of notable regularities. First, the continents tend to be triangular, with their pointed ends to the south. Second, the northern polar ocean is almost entirely ringed by land, from which three continents project southward, while the continental landmass at the south pole is surrounded by water, with three oceans projecting northward. Third, the oceans and continents are arranged antipodally -- i.e. if there is land in one area of the globe, there tends to be water in the corresponding area on the opposite side of the globe.
    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 North Atlantic; and the South Atlantic corresponds -- though less exactly -- to the eastern half of Asia.* 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. The antipodal arrangement of land and seas reflects the tetrahedral plan of the earth. If one corner of the tetrahedron is placed in Antarctica, at the south pole, the other three lie in three vast blocks of very ancient, Archean rocks in the northern hemisphere: the Canadian shield, the Scandinavian shield, and the Siberian shield, and the three edges correspond to the three roughly meridional lines running through the three pairs of continents: North and South America, Europe and Africa, Asia and Australia.**

*Rupert Sheldrake likens the earth to a developing organism, and says that the existence of an ocean at the north pole and a continent at the south pole may be the culmination of a morphogenetic process: 'Such a morphological polarization of a spherical body is very familiar in the realm of biology; for example, in the formation of poles in fertilized eggs' (The Rebirth of Nature, Bantam, 1991, p. 161).
**J.W. Gregory suggested that in the Upper Paleozoic the tetrahedron was the other way up, with one corner at the north pole. Instead of a continuous southern ocean-belt separating triangular points of land, there was then a southern land-belt, supported by three great equidistant cornerstones: the Archean blocks of South America, South Africa, and Australia.
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