igneous rocks. formation of igneous rocks igneous comes from the latin word ignis, which means...
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Formation of Igneous Rocks Igneous comes from the
Latin word ignis, which means fire
Intrusive igneous rocks are formed when magma hardens beneath Earth’s surface
Extrusive igneous rocks are formed when lava hardens on Earth’s surface
Classification of Igneous Rocks
Texture and composition are two characteristics used to classify igneous rocks
Texture describes the appearance of an igneous rock based on its size, shape, and arrangement of its interlocking crystals
Composition of igneous rocks are based on the proportions of light and dark minerals in the rock
Texture
Coarse-grained texture is caused by slow cooling resulting in larger crystals
Fine-grained texture is caused by rapid cooling resulting in smaller, interconnected mineral grains
Gabbro
Andesite
Texture continued
Glassy texture is caused by very rapid cooling
Porphyritic texture is caused by different rates of cooling resulting in varied sized minerals
Obsidian (compact glass)
Classification of Igneous Rocks
Composition of igneous rocks are based on the proportions of light and dark minerals in the rock
There are four types of composition Granitic Andesitic Basaltic Ultramafic
Igneous Rock Summary
Igneous rocks form when magma or lava cools and hardens
Intrusive rocks form from magma deep within Earth
Extrusive rocks form from lava at Earth’s surface
Igneous rocks can be classified according to texture and composition
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