Studies of our planet's crust, or lithosphere, suggest that it's not a single solid layer at all. This video illustrates the process of scientific inquiry by studying the evolution of our understanding of plate tectonics, the dynamics of those ever-shifting slabs of earth we call solid ground. Beginning with Alfred Wegener's hypothesis of continental drift, the program discusses major and minor plates, types of plate boundaries, and the concepts of spreading and subduction. Earthquakes and volcanoes are also addressed.

Encoded with permission for digital streaming by Infobase on Apr. 28, 2006. Learn360 is distributed by Infobase for Films for the Humanities & Sciences, Cambridge Educational, Meridian Education, and Shopware.

Pangaea and Continental Drift (3:39) -- Magnetic Reversals (2:16) -- Mechanical Layers of the Earth (3:09) -- Earth's Changing Surface (3:08) -- Tectonic Plate Boundaries (2:40) -- Faults and Earthquakes (3:32) -- Strata and Shield Volcanoes (4:35).