Q:

How are felsic, intermediate and mafic igneous rocks different?

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Quick Answer

Felsic, intermediate and mafic igneous rocks differ in their mineral composition. Felsic rocks are light in color and are composed of feldspars and silicates. Mafic rocks are darker and are composed of magnesium and iron. Intermediate rocks are composed of the minerals amphibole and feldspar and contain a combination of light and dark minerals.

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Full Answer

Igneous rocks are formed by the cooling and crystallization of magma. The temperature of cooling determines which types of minerals are found in the rock and helps scientists classify the rock as felsic, intermediate or mafic. Rocks that begin their cooling at low temperatures are rich in minerals containing silicon, potassium and aluminum. High temperature igneous rocks contain minerals higher in calcium, sodium, iron and magnesium. Ultramafic rocks are a fourth classification of igneous rock. These rocks are rare on the Earth's surface and contain low amounts of silica the minerals olivine, plagioclase feldspars and pyroxene.

The temperature of cooling igneous rock creates a difference in the texture of the rock. A gradual cooling of magma creates large crystals. Magma that cools fast produces smaller crystals. If volcanic magma cools very quickly on the Earth's surface, obsidian glass is the result. Obsidian glass contains no crystalline structures.

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Related Questions

  • Q:

    What type of igneous rock is rich in iron and magnesium?

    A:

    Mafic, or basaltic, igneous rocks contain a greater portion of iron and magnesium than silica, and they are often much darker in color, typically black, dark brown or dark gray, compared to the lighter-colored igneous rocks which contain a high silica content. Mafic igneous rocks include basalt, gabbro, scoria, dolerite and tachylite. Like all igneous rocks, mafic rocks are formed from magma.

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    What are some facts about igneous rocks?

    A:

    Some facts about igneous rocks include that they are glassy in nature, that pumice igneous rock is the lightest type of rock on Earth, and that the moon is made of igneous rocks. Igneous rocks come from molten magma and have two main versions: basalt and pumice.

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    Why does land heat and cool faster than water?

    A:

    Because of water's fluid molecular composition, it takes longer to heat and cool than land, which has a molecular structure that is more static and dense. Convective movements and the thermal capacities of bodies of water cause them to have a longer heat and cool time than land. Additionally the typically darker color of land gives it a higher propensity to trapping heat.

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    What is Earth's atmosphere made of?

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    Earth's atmosphere, which is around 300 miles thick, is mainly made of nitrogen and oxygen, although there are many other trace substances in its composition. Trace substances make up only 1 percent of the bulk of the atmosphere while nitrogen (78 percent), oxygen (21 percent) and argon (1 percent) make up the rest.

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