This site provides information about the geologic relationships of rock layers, as well as much about geologic time and the history of Earth.

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

Identify geologic time periods and the animals and plants that lived during that time period.

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...

Resource explores the history and geology of the Cascade Mountains. Content includes a geologic story, virtual field trip, a look at plate tectonics and the rocks & minerals found in the Cascade Mountains, geologic maps, and more.

This illustrated timeline from the Lunar and Planetary Institute provides a journey through four-and-a-half billion years of time from the birth of our solar system to its current existence today.

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....

Photos, illustrations, 3D graphs and animations are part of this investigation into the geology and landforms of the Grand Canyon. Learn detailed information on the formation of the canyon, the rock layers, and the prehistoric life that...

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.

Explore geologic time of the Earth and learn how radioactive decay helps to establish a timeline.

An learning activity to help young scholars grasp the concept of relative dating and geologic time.

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

This site from Digital Library for Earth System Education provides materials for students and teachers on a huge array of topics. Search site by topic, grade level, and desired output (such as lesson plan, case study, assessment or...

A very comprehensive article about the ice-free corridor which was possibly the passageway for Paleoindians to enter North America. The discussion includes geology as well as anthropolpgy.

Discover the fascinating world of the stingray by learning about its distribution, behaviors, habitats, geological time periods, and classification through videos, news, photos, descriptions, and external links.

An explanation of the Earth's atmosphere and how it has evolved over geologic time.

The Understanding Evolution site provides evidence for evolution in biogeography utilizing relative dating, geography, and plate tectonics.

This dinosaur site, containing eight different sections, includes topics such as: 101 crazy theories about dinosaur extinction, the pattern and timing of extinction, evidence for late cretaceous climatic change, gradual extinction and...

Many of the interesting landmarks around the world are formed over time by natural processes familiar to us in our everyday lives. This still collage produced for Teachers' Domain features images of a variety of beautiful natural wonders.

Explore life on ancient Earth with this site! Students can walk with dinosaurs to see what Earth looked like or investigate Earth's history. The site includes articles, pictures, timelines, and lots more.

Instructional module focusing on the rock cycle. Discussion includes the concept of uniformitarianism and how earth materials change from one form to another. The site also includes an interactive practice quiz and links relating to the...

The breathable air we enjoy today originated from tiny organisms, although the details remain lost in geologic time. Scientific American helps uncover this mystery.

What did Denver look like millions of years ago? Find out the answer to this and see how it has changed over time. There is also a list of parks to visit in Colorado.