Q:

How do rocks form?

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Quick Answer

Rocks are formed in three primary ways, and each method produces rocks with different characteristics. Rocks are either classified as sedimentary, igneous or metamorphic, depending on the manner in which they were formed. Most rocks encountered in everyday life are sedimentary, although some igneous rocks, such as granite, are also common.

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Sedimentary rocks are formed over thousands or millions of years as fine particles are compressed to form stones. As the layers accumulate, they impart incredible pressure on the bottom layers. Sandstone, limestone, shale and gypsum are all examples of sedimentary rocks. Sedimentary rocks often form in deltas and rivers because the constant flow of the river drags sediments from the river bed and deposits them in a confined area.

Igneous rocks are formed when molten rocks cool. Magma and lava spewing from volcanoes are the two most common source for igneous rocks. Granite, pumice, obsidian and scoria are all examples of igneous rocks.

Metamorphic rocks begin as either sedimentary or igneous rocks. Sometimes such rocks end up being moved into the deep parts of the Earth’s crust, where temperatures are high and pressures are extreme. These unusual conditions serve to heat and change the rocks. Marble, slate and gneiss are examples of metamorphic rocks.

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Related Questions

  • Q:

    How are metamorphic rocks classified?

    A:

    Metamorphic rocks are primarily classified according to mineral composition and texture, similar to how igneous or sedimentary rocks are classified. However, the forces that form metamorphic rocks, namely pressure, heat and chemically active fluids, can produce a wide range of different substances, which makes classifying these rocks much more difficult.

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  • Q:

    Where can metamorphic rocks be found?

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    Metamorphic rocks are most often found in mountainous regions though they can be seen wherever there are signs of geological upheaval in an area. This type of rock is formed by the transformation of another rock type, a change that is usually triggered by tremendous heat, pressure or other violent phenomena. The forces that cause metamorphic rocks to form are so great that they change not only the appearance but also the chemical composition of an existing rock.

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    What are all of the uses for granite?

    A:

    Granite is one of the strongest, most attractive rocks naturally produced, which makes it valuable to builders and homeowners for a number of interior and exterior applications. Granite is used in projects to provide elegance and quality.

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    What are four types of pyroclastic materials?

    A:

    Four types of pyroclastic materials include ash, lapilli, lava blocks and floating rocks. Pyroclastic materials are ejected during a volcano. Ash is the most common type of pyroclastic material.

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