These models place Earth’s age at approximately 4.5 billion years old.

Particles in the solar nebula condensed to form solid grains, and with increasing electrostatic and gravitational influences they eventually clumped together into fragments or chunks of rock. The constituent metallic elements sank toward the centre of the mass, while lighter elements rose toward the top.

Students could complete the Geologic Time Activity, on the Exploring the Environment website, in which they compare geologic time to the length of a football field, as well as take an in-depth look at the geologic time periods.

Students could complete the Sequencing Time activity in which they create a personal time line in an effort to better understand the geologic time line.

This lesson is based on information included in Fossils, Rocks, and Time, part of the United States Geological Survey website.

Preview the information at this site and decide whether it would be best to print the text ahead of time, or allow students to read it online.

Prerequisite knowledge for this lesson includes the idea that: "Sediments of sand and smaller particles (sometimes containing the remains of organisms) are gradually buried and are cemented together by dissolved minerals to form solid rock again." (, p.

73.) Concepts covered in this lesson, including geologic history, age dating, plate tectonics, timelines, and fossils are prerequisite concepts for understanding the theory of evolution, which is another topic taught at this grade level.The layers of rock at Earth’s surface contain evidence of the evolutionary processes undergone by these components of the terrestrial environment during the times at which each layer was formed.By studying this rock record from the very beginning, it is thus possible to trace their development and the resultant changes through time.It is widely accepted by both geologists and astronomers that Earth is roughly 4.6 billion years old.This age has been obtained from the isotopic analysis of many meteorites as well as of soil and rock samples from the Moon by such dating methods as rubidium–strontium and uranium–lead.The lightest ones (such as hydrogen and helium) that might have formed the first, or primordial, atmosphere probably escaped into outer space.