This learning system provides a variety of materials on Earth and space sciences, such as images, movies, animations, and data sets. Students, teachers, and the general public can access information on the sun and space weather, astronomy, our planet and solar system, current space missions, space-related mythology and art, and geology. For teachers, there are links to tools for navigating the site, ... Full description.

This online calculator helps students understand the classic analogy of relating the geologic time scale to a yard stick. It will help reinforce the concept of the briefness of human history relative to the age of the Earth. Full description.

This document describes how geologic time is approached in discussions of geologic topics. The uses of relative time and absolute time are compared, and a geologic time scale is provided to represent both concepts. References are provided. Full description.

This document provides an explanation of the factors that are thought to drive the growth and retreat of continental glaciers which spread across the Earth during four periods of geologic history. These factors are thought ot be related to variations in Earth's orbit. Full description.

This online pamphlet discusses the concept of geologic time. Topics include the relative and radiometric time scales, the use of index fossils in making age determinations, and current thinking on the age of the Earth. Full description.

This document discusses the history of mass extinctions throughout geologic time, their role in the evolutionary process, and a mathematical model that demonstrates how the evolutionary process might interact with environmental stresses to produce a distribution of extinctions similar to that seen in the fossil record. Full description.

This document briefly discusses the two models most favored for the formation of Earth's atmosphere and compares the present-day atmosphere to the early oxygen-lacking atmosphere. Links to related topics are included. Full description.

This document discusses possible factors that contributed to the formation of massive continental glaciers during four periods of geologic history. Full description.

During most of the last one billion years the globe had no permanent ice. However, sometimes large areas of the globe were covered with vast ice sheets. Users can read and view pictures which help explain what ice ages are, when they occurred, and why they occur. This site, sponsored by the Illinois State Museum, has links to web pages on paleontology of the midwestern United States during the last ... Full description.

This tutorial will help students learn and understand the concepts of geologic time and the age of the Earth. They will investigate the geologic time scale and learn about the use of index fossils and radiometric dating to determine the age of rock formations and fossils. Full description.