Slides in Sedimentary Rock
SEDIMENT - small, solid pieces of a material that come from rocks or living things
Erosion occurs when running water or wind loosen and carry away the fragments of rock.
Desposition - the process by which sediment settles out of the water or wind carrying it.
In addition to particles of rock, sediment may also consist of shells, bones, leaves, stems, and other remains of living things.
Compaction - the process that presses sediments together. Year after year sediment falls on top creating new layers. The weight of the layers further compacts the sediments squeezing them tightly together. This often gives sedimentary rocks a layered appearance.
Cementation is the process in which dissolved materials crystallize and glue particles of sediment together.
It often takes millions of years for compaction and cementation to transform loose sediments into solid sedimentary rock.
A clastic rock is a sedimentary rock that forms when rock fragments are squeezed together.
Shale, Sandstone, Conglomerate, and Breccia are examples of clastic rocks.
Shale - forms from tiny particles of clay
Sandstone forms from the sand on beaches, on the ocean floor, in riverbeds, and in sand dunes. Sandstone is a rock formed from compaction and cementation of small particles of sand.
Conglomerate - A mixture of rock fragments of different sizes with rounded edges.
Breccia - A mixture of rock fragments of different sizes with sharp edges.
Organic rock forms when the remains of plants and animals are deposited in thick layers. "Organic" refers to substances that were once part of living things.
Coal forms from the remains of swamp plants buried in water. As layer upon layer of plant remains build up, the weight of the layers squeezes the decaying plants. Over millions of years, they slowly change into coal.
The hard shells of living things produce some types of limestone. In the ocean, many living things, including coral, clams, oysters, and snails, have shells or pile up as sediment on the ocean floor. Slowly the pressure of overlying layers compacts the sediment.
One common type of limestone is used to make chalk.
Chemical rocks form when minerals that are dissolved in a solution crystallize. For example, limestone can form when calcite that is dissolved in lakes, seas, or underground water comes out of solution and forms crystals.
Gypsum is a chemical rock formed by evaporation.
Sandstone is soft enough to be easily cut into rocks or slabs for building. The White House is built of sandstone.