Talk Origins Archive
Talk Origins Archive: Radiometric Dating and the Geological Time Scale
A lengthy article with lots of information about radiometric dating, including pictures and charts.
US Geological Survey
U.s. Geological Survey: Mud Fossils
Two part lesson allows for students to observe real fossils then make and recover their own fossils using mud.
Other
Utah Geological Survey: How Do Geologists Know How Old a Rock Is?
Geologists generally know the age of a rock by determining the age of the group of rocks, or formation, that it is found in. The age of formations is marked on a geologic calendar known as the geologic time scale. Development of the...