What Is a Sedimentary Rock?

Ripples in beach sand (A) may someday become rock like in the lower picture (B). Click on image for full size (143 Kb) Both images courtesy of Martin Miller, University of Oregon

Someday, the sand that you see at the beach might become a sedimentary rock!

The sand at the beach is made of little pieces of rock that broke off larger rocks. These little broken pieces are called sediment. There are many types of sediment including sand, mud, pebbles, and even dust. It takes a very long time, thousands and thousands of years, but sediments can form a rock if they become stuck together.

Sedimentary rocks record what environments were like a long time ago. Fossils are sometimes preserved in sedimentary rocks too. They record what animals and plants were like thousands or millions of years ago.

Some types of sedimentary rocks are made of special sediment. The particles do not come from other rocks. They can be crystals that form from chemicals in seawater, like in chemical rocks, fossils of ancient plants and animals, like in organic rocks.