To get you thinking Explain how these different layers of rock formed? Why are these layers different colors? Sedimentary Rocks
Bryce Canyon, Utah
Badlands, South Dakota
Weathering Whenever rock is exposed at earth s surface, it is continuously being broken down by weathering. Weathering a set of physical and chemical processes that breaks rock into smaller pieces Sediments small pieces of rock that are moved and deposited by water, wind, glaciers and gravity Sediments range in size from huge boulders to microscopic particles
Weathering Physical weathering occurs when rocks are physically broken down into smaller pieces
Weathering Chemical weathering occurs when minerals in rock are dissolved or chemically changed
Erosion Erosion the removal and transport of sediment There are four main agents of erosion Wind Moving Water Gravity Glaciers
Deposition Deposition occurs when sediments are deposited on the ground or sink to the bottom of a body of water As particles of sediment are being carried by water eventually settle out, layers of sediment will form at the bottom according to size Larger particles will settle to the bottom first, followed by progressively finer particles on the top
Deposition Sediment deposited by wind usually consists of finegrained sand Sediment deposited by glaciers usually consists of materials that vary in size
Lithification Lithification the physical and chemical processes that transform sediments into sedimentary rocks There are two processes that convert loose sediment to sedimentary rock compaction and cementation. Compaction the process in which the volume and porosity of a sediment is decreased by the weight of overlying sediments as a result of burial beneath other sediments
The high water content and flat shape of particles in mud cause it to compact greatly when subjected to the weight of overlying sediments.
Lithification Cementation the process in which minerals precipitate into pore spaces between sediment grains and bind sediments together to form rock
Sedimentary Rock rocks made up of a combination of different types of sediment
Clastic Sedimentary Rocks Clastic sedimentary rocks formed from deposits of loose sediments that accumulate on Earth s surface Classified according to the sizes of their particles Coarse-grained (>2 mm) Medium-grained (1/16 mm to 2 mm) Fine-grained (1/256 mm 1/16 mm)
Coarse-grained rocks Conglomerate rock that is composed of rounded fragments ranging in size from fine mud to boulders
Coarse-grained rocks Breccia a type of conglomerate that is composed of fragments that are angular and have sharp corners
Medium-grained rocks Sandstone rock that is composed of sand sized particles that have been cemented together Porosity the percentage of open spaces between grains in a rock Sandstone can have a porosity as high as 30% Valuable layer as underground reservoirs of oil, natural gas, and groundwater
Fine-grained rocks Shale rock that is composed of clay sized particles that are cemented and compacted together Has low porosity and forms barriers that hinder the movement of groundwater and oil
Shale
Chemical sedimentary rocks Chemical sedimentary rock sedimentary rock that forms when minerals precipitate from a solution or settle from suspension When water evaporates, the minerals that were dissolved in the water are left behind. The minerals left behind form rocks called evaporates.
Chemical sedimentary rocks
Halite
Gypsum
Biochemical sedimentary rocks Biochemical sedimentary rock sedimentary rock that forms from the remains of once-living plants or animals Limestone is the most abundant of these rocks Composed primarily of calcite Coal is also a biochemical rock that formed when ancient fern-like plants that grew in swampy areas Composed primarily of carbon
Coal Fossiliferous Limestone
End of Sedimentary Rocks