Exploratorium
Exploratorium: Chaco Canyon: Observation: How Old Is It?
How is time read on the stone of the Chaco Canyon? Find out systems geologists have for dating rocks and fossils.
CK-12 Foundation
Ck 12: Episd: History of Life
[Free Registration/Login may be required to access all resource tools.] Students will explore ways to study the past to learn about the history of life. Understand how fossils, DNA analysis, and molecular clock help researchers study...