The Rock Cycle

Topics: Igneous rock, Metamorphic rock, Sedimentary rock Pages: 2 (515 words) Published: October 16, 2012
The rock cycle involves of a chain of continual progressions through which earth materials change from one form to another over time. Some processes in the rock cycle happen over millions of years and others occur much more quickly. There is no real starting or completion to the rock cycle; however, it may be appropriate to begin investigating the rock cycle with magma (Bergman 2005). Magma, or molten rock, forms only at certain locations within the earth, mostly along plate boundaries. Magma crystallizes when it is permitted to cool. Most magma never makes it to the surface and it cools inside the earth’s crust. Igneous rocks are formed from cooled magma. If magma cools below the earth’s surface it forms intrusive igneous rocks (gabbro); if it cools above the surface it forms extrusive igneous rocks (basalt) (Armstrong n.d.). As soon as rocks are exposed at the earth’s surface, the eroding or weathering process begins. Physical and chemical reactions caused by contact with air, water, and organic entities cause the rocks to break down. Erosion occurs once rocks are broken down; wind, moving water, and glaciers carry pieces of the rocks away. Moving water is the most conventional vehicle of erosion; every year tons of sediment is carried by major rivers from the mountains to the oceans (Home Training Tools 2012 para.6). Under normal conditions, the force created by the mass of the newer deposits compresses the older, buried sediments. As groundwater moves through these sediments, minerals like calcite and silica precipitate out of the water and coat the sediment grains. These precipitants fill in the pore spaces between grains and act as adhesive, sticking individual particles together. Because of seasonal or annual buildup of sediments cycles layers are seen in exposed sedimentary rocks (Home Training Tools 2012 para.7). If sedimentary rocks or intrusive igneous rocks are not brought to the earth’s surface by uplift and erosion, they may experience even...
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