If Earth's entire history could be compressed into a single year, modern humans would've appeared just 23 minutes ago! Use this video to introduce your students to the concept of geological time (also called deep time); relative age dating of rock via the principles of stratigraphic superposition, original horizontality, and cross-cutting; absolute age dating by radioactive decay; the chemical elements, heavy and light, that make up the planet; and Earth's three main layers: crust, mantle, and core.

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.

Earth History and Formation of the Solar System (3:26) -- Earth's Layers and the Earth System (4:21) -- History of Geology (3:32) -- Dating Rocks (5:03) -- Geological Time (2:33) -- Geology Is an Exciting Science (1:32).