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3.3 Sedimentary rocks form from earlier rocks Sedimentary Rock It comes from the word sediment which means something that settles out of water or air. It develops from layers of sediments that build up on land or underwater. A sandy beach or a muddy lake bottom consist mainly of rock particles. 3 Types of Sedimentary rocks are formed from: Rock particles Plants or shells Re-formation of dissolved minerals from water Rocks form from Rock Particles Rainwater washes away rock particles that are carried to lakes. Strong winds pickup rock dust and send them to distant places. As winds or water currents slow down, the rock particles form layers which forms a rock once they are pressed together like the sandstone. Classwork Answer number 1 and 2 p.95 Forming loose sediment into Rocks By pressing layers of sediments together. Or by holding the particles together by minerals acting as a cement. Rocks form from Shells or Plants The fossil which is the remain of an organism from long ago also produce rocks. Coal forms from plants instead of earlier rocks. Shells and skeletons of ocean organisms form limestone once pressed together. Rocks form from Re-formation of dissolved minerals from water Rock salt and gypsum are formed when minerals forms layers of sedimentary rock at the edge of lakes where the climate is dry. Sedimentary Rocks & Past Conditions Fossils of fish or shells in a layer of rock show that the area was covered by a lake or an ocean long ago. How do sedimentary rocks form in layers? The formation of layers depend on the movement of water Fast water carries big particles Slow A water carries small particles flood carries big particles and small particles CLASSWORK 1- How does the movement of water form layer of rock? 2- How can we know that lakes were present in past conditions?