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Much geological evidence about plate tectonics comes from the continental drift theory. This theory states that all continents were actually a part of one or two supercontients1, and then drifted to their current position in the form of plates.
Scientist and geologists have been able to construct a model of these supercontinent(s) and also confirm by plotting similar geological structures found across continents. Examples of these structures would be Precambrian and Palaeozoic age provinces, cratons, and fold belts. The southern hemisphere suffered a major glaciation 280 million years ago2, and the effects of the glaciation are still seen today. In a grouping model of the super continents, the affected areas appear together. In these ways geologists are able to confirm the existence of the supercontinent(s)
Paleomagnetism provides a major confirmation of continental drift. The paleomagnetic method depends on the fact that when many igneous and sedimentary rocks form, their constituent magnetic particles are aligned according to the prevailing magnetic field of the Earth.
By carefully measuring the declination and inclination of the magnetic field of oriented rock samples when they were formed, geologists can calculate the paleolatitude of the rocks and the location of the paleopole at a given time. The paleolatitudes can be used in the construction of paleographic maps, and the paleopoles in the construction of apparent paths of polar wandering. However, the paleolongitude cannot be determined by the paleo magnetic method. The magnetic-anomaly (magnetic strip) patterns of the past 200 million years and the geometric matching of continental margins have to be used for this calculation.
If the paleopole positions are determined for a sequence of North American rocks of different ages ranging from the early Mesozoic to the present, these positions can be plotted on a map to define a polar-wandering curve for that continent. When the paleopoles of rocks from Europe of a similar age range are also calculated and plotted, the two separate curves clearly converge on the present pole. This convergence strongly suggests that the so-called polar-wandering paths do not represent a wandering of the poles, but rather the drift of the two continents. The individual continents moved off at different times in different directions before taking up their present positions, and their movement paths can be followed via their apparent polar-wandering curves.
Paleogeographic maps have now been constructed for all the continents for all the periods by using a combination of paleomagnetic, geometric-fit, and oceanic-magnetic data. These maps demonstrate how the continents were widely dispersed during the Cambrian Period, gradually moved together during the Palaeozoic Era to form mountain belts, and eventually formed the Pangea super continent during the Permian and Triassic periods, after which they went their own way again during the Mesozoic and Cenozoic eras.
A final test of the continental-drift theory is to consider the past diversity of fossil fauna. During the periods of extensive sea floor spreading, i.e.., early to mid-Paleozoic, mid to late Mesozoic, and the Cenozoic era, there was a considerable volume of oceanic waters displaced, which caused a marine transgression of continental margins. This in turn increased the diversity and population of marine fauna. Conversely, during the period when a super continent construction, i.e.., Permian to Triassic, sea floor spreading stopped and previously active ridges subsided. This caused a marine regression. The rapid fall in sea level eliminates most shallow-water faunal niches, and thus faunal diversity decreases. Continents with such similar fossils, signs of increase and decrease in marine population, is the final proof of the continental-drift theory
1 Roger Osbourne, The Historical Atlas of the world; 2 The Grolier Multimedia Encyclopedia
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