In prior years, students learned that fossils represent the remains of plants and animals that lived long ago. In grades 4-5 students learn that fossils also provide evidence of environmental conditions that existed when the fossils formed. Most fossils are imprints formed when plants or animals died in a watery environment and were covered with mud that eventually hardened into rock. Fossils can also form in other ways, as when dissolved minerals seep into a piece of wood and harden into rock, or an animal is frozen in ice that never thaws. Fossils provide evidence of the kinds of plants and animals that lived on Earth in the past, as well as environmental conditions that prevailed at the time the fossils formed.
Earth and Space Science