University of Phoenix Material

Effects of the Motions of Tectonic Plates Worksheet

From Visualizing Earth Science, by Merali, Z., and Skinner, B. J, 2009, Hoboken, NJ: Wiley. Copyright 2009 by Wiley. Adapted with permission.

Part 1

This diagram was similar to one Alfred Wegener drew to show the distribution of continents 300 million years ago. His theory of continental drift was met with skepticism in the scientific community.

1. Describe three forms of evidence Wegener used to support his ideas of continental drift.
• Continental Margins (Visually land masses fit together like a puzzle)
• Rock layers (similarity on the coast lines as well in a different continent
• Fossil evidence (How some animals were identical on the other side of the world, and how tropical plants were found in Arctic regions.
2. Years later, the continental drift theory reemerged as plate tectonic theory, with two additional pieces of evidence.

Refer to the images above. Discuss in detail the two pieces of additional evidence that supported Wegener’s theory, now known as the theory of plate tectonics.

• One additional piece of evidence was the mapping of the ocean sea floor. When all these investigations about the ocean sea floor were given to scientist, a new light in the composition of the rocks and their distribution was discovered. Wegener's ideas started now to make sense for most geologists, the saddest part is that at this time Wegener was already dead so he could not see his vindication. Samples from the ocean floor were for the first time collected and analyzed. In the 1950's paleomagnetism emerged as a new tool.
• Polar wandering – The migration over the surface of the Earth of the magnetic poles of the Earth through geological time (only the magnetic pole “switches” the geographic pole is always the same). A study during the 1950s showed that