American Geosciences Institute
American Geosciences Institute: Earth Science Week: Texas Rocks
For this investigation, students start exploring the U.S. Geological Survey's (USGS) online version of the geologic map of Texas. The geologic time scale shown will help them figure out how old the rocks are in various parts of Texas.
US Geological Survey
Usgs: Geologic Time
This large U.S. Geological Survey site offers a look at the age of the earth, how radiometric dating is used to calculate it, the major divisions of geologic time, and the classification and use of fossils.
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.