The early hypothesis of continental drift proposed by Alfred Wegener has given way to the Theory of Plate Tectonics. This theory is (as described in Chapter 19 of your textbook) the unifying theory of Geology, and provides Earth scientists with a context for understanding the geological history of our planet. Plate Tectonic theory has been confirmed by many observations during the last 40 years or so.

Among the unique capabilities that the understanding of Plate Tectonics has given geologists is the ability to reconstruct past positions of continental landmasses showing the evolution of those continents from the supercontinent of Pangea to the present day. Maps of continental positions are made possible by studies of Earth's magnetism and the geological record of Earth's magnetic field preserved in igneous and (some) sedimentary rocks.

<a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::Pangea 150 Million Years Ago::/sites/dl/free/0072826967/90780/PlatesMa150.jpg','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif">Pangea 150 Million Years Ago (84.0K)</a>Pangea 150 Million Years Ago

The image above is an reconstruction of Pangea and the arrangment of continental landmasses as they appeared 150 million years ago, shortly after the Atlantic Ocean basin began to open between North America and Africa. The outlines of the modern continents are indicated with a black border so that you might recognize this strange planet. Click on the link below to view a Virtual Vista showing the breakup of Pangea and movement of the continents during the last 150 million years of Earth's history.

Continental Drift (2320.0K)

1. What specific method do geologist employ to reconstruct continental positions?

2. What Plate Tectonic process gives rise to the notion of "continental drift"?

3. How does knowledge of Earth's magnetism combine with knowledge of plate tectonic processes to make this movie possible?