Exploration Through Time

This University of California - Museum of Paleontology web site contains a series of interactive modules that explore the history of life on Earth, while focusing on the processes of science. Each module contains suggested lesson plans and an extensive teacher’s guide.

There's one module that's very good for teaching geologic time.

Birth of the Earth Lesson Plan

Objectives
Students will understand the following:

1. Earth is estimated to be 4.6 billion years old.
2. Certain major events have occurred during this period that are considered important milestones in Earth’s development.
3. Early Earth was very different from our planet as we know it today.
4. Earth has existed as we know it today for only a very short time, relative to the number of years since its origin.

Lesson is here.

Earth's Gravity

In this video adapted from NOVA scienceNOW, investigate the hypothetical scenario of a person falling into a hole through the center of Earth. Astrophysicist Neil deGrasse Tyson illustrates the thought experiment; first he defines the conditions—ignore the effects of air resistance, temperature, and Earth's rotation—and then he travels through the hole. A timer and speedometer show how his speed changes as he falls toward the center of Earth, passes the center, and slows to a stop at the opposite end of the hole.

The Drake Equation

The Drake Equation: Estimating the Number of Civilizations in the Milky Way

Overview
Students estimate the number of civilizations in the galaxy by first estimating the number of craters on the Moon and then by performing estimates of multiple-variable systems culminating in the use of the Drake Equation. In this three-part activity, students use estimation techniques to describe complex situations.

Life Outside Earth

How special are the circumstances that have allowed complex life, like animals and plants, to develop on Earth? In this activity students systematically investigate the time frame for complex life to develop on Earth.