Sedimentary Rocks • How do sedimentary rocks form? • What are the three types of sedimentary rocks? Sedimentary Rocks • compaction • clast • cementation • chemical rock • clastic rock • biochemical rock Sedimentary Rock Formation • Mineral and rock fragments can be transported by water, glacial ice, gravity, or wind. • The sediments eventually are deposited, or laid down, where they can them accumulate in layers. Sedimentary Rock Formation (cont.) • The weight from the layers of sediment forces out fluids and decreases the space between grains during a process called compaction. • Compaction can lead to a process called cementation. Sedimentary Rock Formation (cont.) • When minerals dissolved in water crystallize between sediment grains, the process is called cementation. • Mineral cement holds the grains together. Sedimentary Rock Formation (cont.) What is the difference between compaction and cementation? Sedimentary Rock Identification • Sedimentary rocks that are made up of broken pieces of minerals and rock fragments are known as clastic rocks. • The broken pieces and fragments are called clasts. • Sediment size alone cannot be used to determine the environment where a clastic rock formed. Sedimentary Rock Identification (cont.) clastic from Greek klastos, means “broken” Sedimentary Rock Identification (cont.) • When water becomes saturated with dissolved minerals, particles can crystallize out of the water and form minerals. • Chemical rocks form when minerals crystallize directly from water. The water that once filled this lake bed was saturated with dissolved halite. The water evaporated and crystalline rock salt formed. National Geographic/Getty Images Sedimentary Rock Identification (cont.) • Biochemical rock is a sedimentary rock that was formed by organisms or contains the remains of organisms. • Sometimes the remains or traces of organisms are preserved as fossils in biochemical rock. Sedimentary Rock Identification (cont.) Chemical and biochemical sedimentary rocks are common on Earth’s surface. Sedimentary Rock Identification (cont.) How do chemical and biochemical sedimentary rocks form? • A clastic sedimentary rock is made of clasts of minerals or rock fragments. • When minerals crystallize directly from water, a chemical sedimentary rock results. • A biochemical sedimentary rock contains the remains of living organisms or was formed by organisms. National Geographic/Getty Images During which process does the weight from layers of sediment force out fluids and decrease the space between grains? A. cementation B. crystallization C. compaction D. evaporation Which types of rocks are sedimentary rocks made up of broken pieces of minerals and rock fragments? A. chemical C. fragmented B. biochemical D. clastic Chemical rocks form when minerals crystallize directly from which of these? A. gas B. water C. sediment D. magma Do you agree or disagree? 5. Water can dissolve rock. 6. All sedimentary rocks on earth formed from the remains of organisms that lived in oceans.