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Magma is molten rock that is deep underground within the Earth's mantle and portions on the crust called magma chambers.
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Courtesy of Boise National Forest


If you could travel to the center of the Earth, you would find that it gets hotter and hotter as you travel deeper. The heat is naturally produced by decay of radioactive elements. Within the Earth’s mantle layer it is hot enough that much of the rock is molten. The molten rock is called magma. Magma is so hot that it glows white and is so bright that you’d need sunglasses to look at it! If it flows into an area underground that is less hot, it cools, becomes yellow, and then increasingly deeper shades of red. As it cools slowly, minerals crystallize from the melt forming intrusive igneous rocks like granite.

If magma finds a crack in the Earth and comes to the surface, it is called lava and cools to form extrusive igneous rocks like basalt.

Magmas can be different depending on their chemical composition. Magma is a mixture of elements such as silica, oxygen, iron, sodium, and potassium and not all magmas have the same amounts of each element. As the molten material cools, elements combine to form the common types of silicate minerals, which are the building blocks of igneous rocks. Rocks that form from different types of magma are often made of different minerals.

Last modified June 17, 2003 by Lisa Gardiner.

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The Fall 2010 issue of The Earth Scientist, focuses on rocks and minerals, including articles on minerals and mining, the use of minerals in society, and rare earth minerals, and includes 3 posters!

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