Plate tectonics is the theory used to explain the structure of the Earth’s crust and many of the associated phenomenon. The rigid lithosphere is split into 15 major plates that slowly move on top of the underlying asthenosphere (plastic upper mantle), and this science studies the faulting and folding of the crust along the various boundaries: convergent, divergent and conservative. Thought the concept was only considered to be widely accepted in the 1960s, it was first coined by the German geophysicist Alfred Wegener back in 1915.
His first ideas came form noticing that the continents fit together very closely along the continental shelves- the coastlines would have been subject to erosion and weathering. In addition, during several expeditions on either side of the Atlantic he analysed the rock type and fossil distribution and found a very significant match between the East and West. Distinct 2 billion year old rock types on either side of the ocean appeared to line up perfectly when you put the continents together. In terms of fossils, the water reptile Mesosaurus was found in a band across South Africa and southern South Africa, and the land reptile Lystrosaurus was uncovered right from India, across Africa and into Antarctica.
Other contributors to the theory included Harry Hammond Hess, who conducted a series of surveys of the ocean floors around the world, and found a remarkable pattern that showed up a series of trenches and ridges – with the rocks becoming progressively older when you move away from the ridges. From this he developed his ideas of sea floor spreading that was driven by underlying magma rising from the mantle and pushing the crust outwards at ridges where it would then be spread, and this offered a reasonable explanation for Wegener’s findings.
His work was then reinforced by British geologists Frederick Vine and Drummond Matthews, in what is known as paleomagnetism. It is based on the theory that the Earth’s magnetic poles wander...