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Where do igneous rocks originate?

Where do igneous rocks originate? How are they formed? What are the two categories of igneous rocks? What are the distinguishing characteristics between the two categories of rocks? Basically, igneous rocks are formed after the cooling and solidification of molten rock or magma. Their formation may or may not involve crystallization. Generally, igneous rocks are represented by an interconnecting group of minerals that are silicate in nature. There are two categories of igneous rocks: intrusive and extrusive.

Intrusive igneous rocks originate from magma that is cooled and solidified within the earth or beneath the earth’s surface. Basically, the magma below the earth’s surface is surrounded by country rocks, which are already pre-existing. The cooling of the magma then makes the rocks coarse-grained. Some examples of intrusive igneous rock formations are batholiths and laccoliths, among others. On the other hand, extrusive igneous rocks are rocks that are formed on the surface of the earth and result from the rocks’ partial melting inside the crust and the mantle.

The melted material, which may or may not have gas bubbles and floating crystals, is termed magma. The reason the magma shoots upwards is because it generally less dense than rock from which it originated. After the magma reaches the surface, it may then extrude below the surface of water or air and at this point, it is then called lava. Certain examples of extrusive igneous rocks include basalt and rhyolite, among several others.

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