Sedimentary Rock

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Sedimentary Rocks : 

Sedimentary Rocks

From Sediment to Rock : 

From Sediment to Rock Sedimentary Rocks form from particles deposited by water and wind. Sediment – small, solid pieces of material that come from rocks or living things. Water, wind, and ice can carry sediment and deposit it in layers.

Erosion : 

Erosion Destructive forces are constantly breaking up and wearing away rocks Heat, cold, rain, waves and ice Erosion – occurs when running water or wind loosen and carry away the fragments of rock

Deposition : 

Deposition Process by which sediment settles out of the water or wind carrying it After sediment has been deposited, the processes of compaction and cementation change the sediment into sedimentary rock Sediments include shells, bones, leaves, stems etc  fossils

Compaction : 

Compaction Process that presses sediments together Weight of layers compacts sediments, squeezing them tightly together. Layers are often visible in sedimentary rocks

Cementation : 

Cementation While compaction happens, minerals in the rock slowly dissolve in the water. The dissolved minerals seep into the spaces between particles of sediment Cementation is the process in which dissolved minerals crystallize and glue particles of sediment together Takes MILLIONS of years

Formation of Sedimentary Rocks : 

Formation of Sedimentary Rocks Geologists classify sedimentary rocks according to the sediments that make up the rocks. There are 3 major groups:

1. Clastic Rocks : 

1. Clastic Rocks Most sedimentary rocks are made up of broken pieces of other rocks A clastic rock is a sedimentary rock that forms when rock fragments are squeezed together Grouped by size of rock fragments, or particles.

1. Clastic Rocks : 

1. Clastic Rocks Ex 1) Shale – forms from tiny particles of clay. For shale to form, water must deposit clay particles in very thin, flat layers, one on top the other. Shale feels smooth and splits into flat pieces

1. Clastic Rocks : 

1. Clastic Rocks Ex 2) Sandstone – forms from sand on beaches, on the ocean floor, in riverbeds, and in sand dunes. Compaction & cementation of sand particles. Most sand particles consist of quartz. Sandstone contains many small holes and can absorb water through these holes.

1. Clastic Rocks : 

1. Clastic Rocks Ex 3) Conglomerate & Breccia – mixtures of rock fragments of different sizes

2. Organic Rocks : 

2. Organic Rocks Forms where the remains of plants & animals are deposited in thick layers. Ex 1) Coal–from swamp plants buried in water Ex 2) Limestone – hard shells of some living things produce some kinds of limestone. Corals, clams, oysters and snails have shells made of calcite.  Chalk

3. Chemical Rocks : 

3. Chemical Rocks Form when minerals that are dissolved in a solution crystallize.

Uses of Sedimentary Rock : 

Uses of Sedimentary Rock Used as building materials – soft enough to be cut into slabs or blocks. The White House is made of sandstone