Evidence for Continental Drift

Wegener had many pieces of evidence to support his assertion that the continents had broken apart and drifted to their modern locations. For one, the shapes of the continents match like puzzle pieces. This is especially true of the coastlines of South America and Africa. Wegener also collected rock, fossil, and climate evidence to support his theory of continental drift.


Rock Evidence

When Wegener reassembled the continents, he noticed that now-separated plates had similar mountain ranges and rock types. For example, the Appalachian Mountains on the eastern side of the North American plate were structurally and compositionally similar to mountains in Europe and Greenland. He made similar observations of the rock types in western Africa and eastern South America.


Fossil Evidence

Wegener also noticed that similar fossils of plant and animals were found in rocks of the same age on continents that are separated today. Fossils of Glossopteris were found spread across Antarctica, South America, Africa, Australia and India. Fossils of the land-dwelling reptiles Cynognathus and Mesosaurus were found on both Africa and South America, while fossils of Lystrosaurus were found on Antarctica, India, and Africa. Wegener reasoned that these land-dwelling animals could not have swum the great distances that exist between the continents today; therefore, the continents must have been connected when these animals lived on Earth.


Climate Evidence

In Wegener's mind, the drifting of continents after the break-up of Pangaea explained not only the matching fossil occurrences but also the evidence of dramatic climate changes on some continents. For example, the discovery of fossils of tropical plants (in the form of coal deposits) in Antarctica led to the conclusion that this frozen land previously must have been situated closer to the equator, in a more tropical climate where lush, swampy vegetation could grow.

Additionally, coal deposits found today in Europe and North America were created from plants that grew and decayed in tropical swamps about 300 million years ago. Therefore, these continents must have once been located much closer to the equator in Earth's geologic past. Other mismatches of geology and climate included distinctive fossil ferns (Glossopteris) discovered in now-polar regions and the occurrence of glacial deposits in present-day arid Africa, such as the Vaal River valley of South Africa.




Sources
http://pubs.usgs.gov/gip/dynamic/historical.html (public domain)
http://openlearn.open.ac.uk/mod/resource/view.php?id=172173&direct=1 (CC BY-NC-SA)