1. Sedimentary Rocks 2006 Prentice Hall Science Explorer- Earth Science Liz LaRosa http://www.middleschoolscience.com 2009http://www.middleschoolscience.com Images from Geology.com unless otherwise noted

2.  Most sedimentary rocks are formed through a series of processes: erosion, deposition, compaction and cementation.

3.  Destructive forces are constantly breaking up and wearing away all the rocks on Earth’s surface.  These forces include heat and cold, rain, waves, and grinding ice. These forces of erosion form sediment which are small solid pieces of material that come from rocks or living things.  In erosion, running water, wind, or ice loosen and carry away fragments of rock.

4.  Eventually, the moving water, wind or ice slows and deposits the sediment in layers.  Deposition is the process by which sediment settles out of water or wind carrying it.

5.  The process that presses sediments together is compaction. Thick layers of sediment build up gradually over millions of years. These heavy layers press down on the layers beneath them. The weight of new layers further compacts the sediments, squeezing them tightly together. The layers often remain visible in sedimentary rock.

6.  While compaction is taking place, the minerals in the rock slowly dissolve in the water.  Cementation is the process in which dissolved minerals crystallize and glue particles of sediment together. In cementation, dissolved minerals seep into the spaces between particles and then harden.

7.  Sedimentary Rocks are formed at or near the Earth’s surface.  No heat and pressure involved  Strata – layers of rock  Stratification – the process in which sedimentary rocks are arranged in layers Stratification

8. http://www.fi.edu/fellows/payton/rocks/create/sediment.htm  Sedimentary rock is formed by erosion  Sediments are moved from one place to another  Sediments are deposited in layers, with the older ones on the bottom  The layers become compacted and cemented together Summary: Formation of Sedimentary Rock

9.  Geologist classify sedimentary rocks according to the type of sediments that make up the rock.  There are three major groups of sedimentary rocks: clastic rocks, organic rocks, and chemical rocks.

10. A clastic rock is a sedimentary rock that forms when rock fragments are squeezed together. Breccia is a term most often used for clastic sedimentary rocks that are composed of large angular fragments (over two millimeters in diameter). The spaces between the large angular fragments can be filled with a matrix of smaller particles or a mineral cement that binds the rock together. Conglomerate- is a term used for clastic rocks with rounded edges. Breccia is a term most often used for clastic sedimentary rocks that are composed of large angular fragments (over two millimeters in diameter). The spaces between the large angular fragments can be filled with a matrix of smaller particles or a mineral cement that binds the rock together. Conglomerate- is a term used for clastic rocks with rounded edges.

11. An organic rock forms where the remains of plants and animals are deposited in thick layers. Coal is an organic sedimentary rock that forms from the accumulation and preservation of plant materials, usually in a swamp environment. Coal is a combustible rock and along with oil and natural gas it is one of the three most important fossil fuels. Coal is an organic sedimentary rock that forms from the accumulation and preservation of plant materials, usually in a swamp environment. Coal is a combustible rock and along with oil and natural gas it is one of the three most important fossil fuels.

12. Chemical rock is formed when minerals that are dissolved in a solution crystallize. Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO 3 ) in the form of the mineral calcite. It most commonly forms in clear, warm, shallow marine waters. It is usually an organic sedimentary rock that forms from the accumulation of shell, coral, algal and fecal debris. Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO 3 ) in the form of the mineral calcite. It most commonly forms in clear, warm, shallow marine waters. It is usually an organic sedimentary rock that forms from the accumulation of shell, coral, algal and fecal debris.

13.  People have used sedimentary rock throughout history for many different purposes, including building materials and tools. Examples  Arrowheads  Sandstone and Limestone used in building materials  Limestone is also used in making cement and steel.