A lengthy article with lots of information about radiometric dating, including pictures and charts.

A lengthy scholarly article that discusses the geologic time scale, its history of development, age-dating events that occurred in different eras, and how absolute and relative dating are used to assess the ages of the Earth and Moon....

This is a good source for getting an in-depth description of using radioactive decay to measure the ages of rocks. In addition to describing the process of radiometric dating, this resource also includes a geologic time scale and four...

This is a good resource for anyone who wants to understand the historical development that led to our understanding of relative dating. This site also has links to index fossils and a table of geologic time.

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...

This in-depth article illustrates the concept of geologic time, and helps the learner understand why fossils are rare.