Rock Cycle.

... (www.canadianrockhound.com/ junior/rock_cycle.html) Liana Herzig Geology 3/7/04 Rocks are composed primarily of minerals and can be an combination of different minerals or can be composed of one mineral. Over 3500 minerals have been identified; most of these can be found in the earth's crust. Some of the earth's minerals are exceedingly popular - fewer than 20 minerals compose more than 95% of the earth's crust. There are three different ways rock can be created on earth and therefore there are three main classifications of rock, based on the three processes - igneous, sedimentary, and metamorphic. Igneous rocks are formed from the molten liquid minerals that lie below the earth's crust. They're formed from magma that cools beneath the earth's surface or from lava that cools upon the earth's surface. These two methods of igneous rock formation are known as intrusive and extrusive, respectively.

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