1. Mrs. Hutson

2.   Sand is a product of weathering, which breaks rock into pieces.  Over time, sand grains may be compacted, or compressed, and then cemented together to form a rock called sandstone.  Sandstone is just one of many types of sedimentary rock. Where does Sand come from?

3.   Wind, water, ice, sunlight, and gravity all cause rock to physically weather into fragments.  Through the process of erosion, these rock and mineral fragments, called sediment, are moved from one place to another.  Eventually, the sediment is deposited in layers. As new layers of sediment are deposited, they cover older layers. Older layers become compacted. Origins of Sedimentary Rock

4.   Sedimentary rock forms at or near the Earth’s surface.  It forms without the heat and pressure that are involved in the formation of igneous and metamorphic rocks. Origins of Sedimentary Rock

5.   The most noticeable feature of sedimentary rock is its layers, or strata.  A single, horizontal layer of rock is sometimes visible for many miles. Road cuts are good places to observe strata.  Figure 1 shows the spectacular views that sedimentary rock formations carved by erosion can provide.

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7.   Sedimentary rock is classified by the way it forms.  Clastic sedimentary rock forms when rock or mineral fragments, called clasts, are cemented together.  Chemical sedimentary rock forms when minerals crystallize out of a solution, such as sea water, to become rock.  Organic sedimentary rock forms from the remains of once-living plants and animals. Composition of Sedimentary Rock

8.   Clastic sedimentary rock is made of fragments of rocks cemented together by a mineral such as calcite or quartz.  Figure 2 shows how clastic sedimentary rock is classified according to the size of the fragments from which the rock is made.  Clastic sedimentary rocks can have coarse-grained, medium-grained, or fine-grained textures. Clastic Sedimentary Rock

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10.   Chemical sedimentary rock forms from solutions of dissolved minerals and water.  As rainwater slowly makes its way to the ocean, it dissolves some of the rock material it passes through.  Some of this dissolved material eventually crystallizes and forms the minerals that make up chemical sedimentary rock. Chemical Sedimentary Rock

11.   Most limestone forms from the remains, or fossils, of animals that once lived in the ocean.  For example, some limestone is made of the skeletons of tiny organisms called coral. Organic Sedimentary Rock

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13.   Another type of organic sedimentary rock is coal.  Coal forms underground when partially decomposed plant material is buried beneath sediment and is changed into coal by increasing heat and pressure.  This process occurs over millions of years. Coal

14.   Many features can tell you about the way sedimentary rock formed.  The most important feature of sedimentary rock is stratification.  Stratification is the process in which sedimentary rocks are arranged in layers.  Strata differ from one another depending on the kind, size, and color of their sediment. Sedimentary Rock Structures

15.   Sedimentary rocks sometimes record the motion of wind and water waves on lakes, oceans, rivers, and sand dunes in features called ripple marks, as shown in Figure 5.

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