Some layers are very thin, some are thick. Sometimes changes in the colors of the layers are caused by the streams bringing in a different kind of sediment. Geologists can someimes find traces of ash from large volcanic eruptions in the rocks. Sedimentary rocks preserve information from the distant past for us. Sometimes they contain fossils.
Fossils are the remains of animals and plants that lived on earth many millions of years ago.
The layers in the rocks tell us about long-ago changes in the landscape. Let's look at how these rocks form and at what happens to them. Elizabeth Anne Viau and her licensors. All rights reserved. This material may be used by individuals for instructional purposes but not sold.