Though it was a Dutch cartographer, Abraham Ortelius, who was the first to work on the concept of symmetrical coasts on the Atlantic Ocean's sides.

This theory has explained the origin of continents and ocean basins.

Continental drift theory was given by Alfred Wegener in 1915.This drifting takes millions of years to complete this process. Continental Drift: The movement of continents across the ocean bed is known as continental drift.

As described on the next page, the plate tectonics revolution came about following the discovery of additional evidence that supported the movement of continents, but more importantly the development of a convincing explanation for the mechanism that drives such movement.Continental Drift Theory Continental Drift Theory It was not until the 1960s that most geologists became convinced that the core component of Wegener's hypothesis-the movement of continents-was correct. For the next 40 years, geologists largely disregarded the idea of continental drift. Wegener suggested that tidal forces in Earth's crust were responsible for moving the continents, but this mechanism was viewed by both his contemporaries and modern geophysicists as incorrect. One important reason for this is that Wegener had not presented a convincing mechanism that could move continents across Earth's surface. Despite all of this evidence, which was presented during the 1910s and 1920s, few geologists accepted the hypothesis that the positions of the continents had changed over time. This evidence ranged from the shapes of the continents themselves, to clues from both the fossil record and the physical rock record. Such glacial erratics have a different composition because they traveled with the glacier, originating in an area with a very different geological history.Īlfred Wegener and other early supporters of the hypothesis of continental drift provided diverse evidence in support of their view that the positions of the continents had changed over time. Till is composed of all of the rocks and sediments that were carried along by the glacier as it moved, including clay, sand, and cobbles and boulders that frequently are very different in composition from the surrounding bedrock.

(Imagine the marks that would be left behind if you dragged a rake behind yourself while walking along a sandy beach glaciers leave similar types of marks behind.) Glaciers also leave behind a distinctive type of sediment called till when they melt. Glaciers carry rocks along at their base as they move and these rocks leave behind scratch marks called striations in the bedrock that are parallel to the direction of glacial flow. Geological features left behind by the movement of glacial ice provided an additional line of evidence of support for Wegener and his colleagues that continental drift had occurred. Glacial Indicators and Distinctive Rock Sequences The red points, which indicate places where fossils of Mesosaurus have been found, suggest a much more constrained range when considered in the context of the Permian paleogeography when these animals were alive. The map below shows the positions of the continents 275 million years ago, during the Permian period. The distribution of Mesosaurus, of course, makes much more sense if the continents were once connected and subsequently broke apart. The land bridge hypothesis, however, did not stand up to scrutiny: 1) there is no evidence for a sunk bridge under the ocean and 2) continental crust cannot sink below oceanic crust because it is less dense. This distribution presents an immediate conundrum: how was this small reptile able to survive a journey across the entire Atlantic ocean? At one point, some paleontologists and geologists argued that a land bridge (that would have facilitated the movements of organisms from one continent to the other) must have once connected South American with Africa, but later sunk.

Abraham ortelius hypothesis evidence