Geology Crafts for Kids: 50 Nifty Projects to Explore the Marvels of Planet Earth by Alan Anderson, Gwen Diehn, and Terry Krautwurst
Includes a nice variety of artsy activities accompanied by excellent child-friendly nonfiction about earthquakes, volcanoes, and more

The Magic School Bus: Inside the Earth by Joanna Cole and Bruce Degen
Who can resist Ms. Frizzle? Even my sixth graders were eager listeners.

How the Earth Works: 100 Ways Parents and Kids Can Share the Secrets of the Earth by John Farndon
Absolutely essential! My textbook for writing this unit!

The Big Rock by Bruce Hiscock

The Pebble in My Pocket: A History of Our Earth by Meredith Hooper and Chris Coady

Rocks in His Head by Carol Otis Hurst, Illustrated by James Stevenson
A very enjoyable work of fiction about a father who loves rocks

Geography from A to Z: A Picture Glossary by Jack Knowlton, Illustrated by Harriett Barton
Especially handy for learning to draw various landforms

Earthquake Games: Earthquakes and Volcanoes Explained by 32 Games and Experiments by Matthys Levy and Mario Salvadori

Mountain Dance by Thomas Locker
Gorgeous paintings of the earth-changing processes studied in this unit

The Handy Geography Answer Book by Matt T. Rosenberg
Valuable resource for answering the questions of the kid who can stump you!

Earth Science for Every Kid: 101 Easy Experiments That Really Work by Janice VanCleave

Eyewitness: Earth by Susanna Van Rose