Sediments stick together Sedimentary rock

What is it? Sedimentary rock is accumulated sediment that has been compacted, or pushed together, or cemented together. Sedimentary rock comes in three families – clastic, checmical, and organic. Silt, clay, and sand are the most common sediments on the planet.

Clastic sedimentary rock Rock that are cemented together by water- carried minerals are called conglomerates. Sandstone is a common example of a clastic rock. Shale is another example – it is layered clay fragments cemented together into layers.

Chemical sedimentary rock Minerals once dissolved in water that stick with sediments are in the chemical family. Gypsum and halite are common examples. The Bonneville Salt Flats in Utah contain many evaporite deposits.

Organic sedimentary rock Organic rock is formed from living things. Marine organisms like clams and oysters have shells made of limestone. Chalk is the remains of marine single-cell organisms. The chalk used on the blackboard is actually Gypsum.

Other interesting features Stratification is layering of rock in different sizes. Ripple marks are evidence of changes by wind and water preserved on rock. Mud cracks result from muddy deposits that harden and shrink. Fossils are sometimes neatly preserved in sedimentary rocks.