The Three Basic Types of Rocks
A special education science teacher and administrator, Gregory Gerkens most recently served as assistant principal of Eastern Suffolk BOCES in Centereach, New York. In a previous position, Greg Gerkens is a special education earth science teacher. He enjoys teaching children about the many forms of rocks. 

There are three basic types of rocks: igneous, metamorphic, and sedimentary. Igneous rocks form when the molten rock in the earth’s crust cools and crystallizes. This cooling can take place deep within the earth or on the surface when volcanic eruptions eject molten rock. Igneous rocks are usually very hard. Examples include andesite, dacite, and nepheline.

Metamorphic rocks, as the name suggests, are created by some type of metamorphosis (change of state). They are formed deep within the earth's surface when igneous or sedimentary rocks are subjected to intense pressure and heat, which slowly causes them to become fundamentally different from the original rock. They often have a shiny appearance. Examples include marble and gneiss. 

Sedimentary rocks are formed when debris or sediments gather together and are compacted and cemented. These are rocks made from fragmented materials that accumulate and harden over the years. They are relatively soft and can be easily broken. Examples include limestone and conglomerate.
The Three Basic Types of Rocks
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The Three Basic Types of Rocks

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