Sedimentary rocks contain information about what earth's environment was like in the past.
Fossils in sedimentary rocks provide evidence of how life on earth evolved under changing environmental conditions. In doing this week's lab, you can learn how to find clues about earth's past that are preserved in these rocks. The source of sediments is pre-existing rock that has been exposed at earth's surface and undergone weathering. Both solid grains and dissolved materials are carried by glaciers and rivers, or move in landslides, winds or under ocean waves. Solid grains are deposited when the flows that transport them slow and lose energy.