S E D I M E N T A R Y R O C K From Sediment to Rock Sedimentary rock forms from particles deposited by water, wind, and ice. Sediment is small, solid pieces of material that comes from rocks or living things. Water, wind, and ice can carry sediment and deposit it in layers. • But what turns these sediments into solid rock? Let’s see…… What turns sediments into solid rock? • Step 1 - Erosion • Step 2 - Deposition • Step 3 - Compaction • Step 4 - Cementation Erosion • Step 1 - Erosion Erosion occurs when running water or wind loosen and carry away the fragments of rock. What turns sediments into solid rock? • Step 2 - Deposition • Eventually, the moving water or wind slows and deposits the sediment. Deposition is the process by which sediment settles out of the water or wind carrying it. What turns sediments into solid rock? • Step 3 - Compaction • Gradually, over millions of years, thick layers of sediment build up. These layers are heavy and press down on the layers beneath them. Compaction is the process that presses sediments together. What turns sediments into solid rock? • Step 4 - Cementation Cementation is the process in which dissolved minerals 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. What turns sediments into solid rock? Types of Sedimentary Rock There are three major groups of sedimentary rocks: 1. Clastic rocks - rock fragments are squeezed together. Clastic – made of fragments of rock cemented together with calcite or quartz 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. Types of Sedimentary Rock There are three major groups of sedimentary rocks: 2. Organic rocks - remains of plants and animals are deposited in thick layers. • 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. Organic sedimentary – remains of plants and animals 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. Types of Sedimentary Rock There are three major groups of sedimentary rocks: 3. Chemical rocks - when minerals that are dissolved in a solution crystallize. Chemical sedimentary – minerals crystallize out of solution to become rock Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO3) 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. Uses of Sedimentary Rocks • You may be surprised to learn that the White House in Washington, D.C., is built of sandstone. • Limestone also has many industrial uses. • Limestone is also used in making cement.