Broad Analysis of Igneous Rocks in Earth’s Geology

Out of the three different types of rocks, igneous rocks are by far the most abundant rock on the earth’s surface. From the oceans to the mountains, you will find igneous rocks everywhere and it is easy to see why.

Igneous rocks are a result of solidified magma. Magma is found underneath the earth’s surface all over. Mountains are usually volcanoes; either extinct, dormant or active. Volcanoes contain magma. Magma is cooling all the time. This would mean that the rocks that form from lava spews, or pyroclastic debris would be igneous.

Since volcanoes are also found below sea level, oceans would also have igneous rocks in them. In the article “Mantle Plumes and Moutains” written by J. Brendan Murphy, Gary L. Oppliger, George G. Brimhall, Jr. and Andrew Hines, they talk about hot spots lying beneath the oceanic crust. When these erupt, the magma forms rocks on the ocean floor: these rocks are igneous. They also talk about continental crust overriding hot spots. This is why islands such as the chains in Hawaii have so many volcanoes. And anywhere volcanoes are - igneous rocks are.

Subduction is also a huge reason that igneous rocks are so abundant. The Sierra Nevada is apparently made up of large granitic bodies, placed there through the process of subduction. (Murphy, 1999) The article goes on to say that the subduction leads to the “deformation of rocks and igneous activity, which combine to form mountains.”

Possibly the biggest reason for the abundance of igneous rocks would be the theory of plate tectonics. This theory tells of the spanning of oceans from the tearing apart of continents. When the magma ascends from the asthenosphere, the cooled magma generates the new lithosphere. (Murphy, 1999) This creates oceans. Oceans make up a very large portion of the earth.

Igneous activity is very common also because in the rock cycle, extreme heat and pressure turns metamorphic and sedimentary rocks into magma which in turn cools and turns into igneous rocks. This is a common cycle and with the abundance of mountains and oceans, igneous rocks are very common. As long as the plates continue to move, magma will form and make new rocks, and as long as the rock cycle continues, there will be igneous rocks.

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