Curated OER
National Park Service: What Is Geologic Time?
A discussion of geologic time, along with a presentation of evidence for the time span involved.
CK-12 Foundation
Ck 12: Biology: How Earth Formed
[Free Registration/Login may be required to access all resource tools.] Describes the Earth's formation.
US Geological Survey
Usgs: What Is Geologic Time?
Understand the evidence for ancient earth and the geologic time scale. Learn on this site how the earth can help scientist date discoveries.