People today can never know exactly what was happening on Earth many millions of years ago, but rocks and fossils have helped scientists learn a great deal. From rocks that have been carved by erosion to skeletons of early humans, rocks and fossils help show us the ways Earth has changed—and what is in store for the future. HI-LO/reading level grade 3, 32 pages each, full-color photographs, paperback. Save $1 per book when ordering 10 or more copies.