History of Rock

Topics: Igneous rock, Plate tectonics, Magma Pages: 2 (552 words) Published: December 22, 2012
Write a 500- to 750-word explanation regarding the role of plate tectonics in the origin of igneous rocks.

To begin, igneous rocks come from magma, and magma is related to plate tectonics. Magmas differ in composition, temperature and viscosity. This is a major identifier of igneous rocks, is that they were once molten and magma Plate tectonics are the theory that the Earth’s lithosphere, which is the outer rigid shell is composed of several different pieces, or “plates” that float on a ductile mantle, kind of like floating on water. These plates collide, split apart and slide past each other. When this type of activity occurs it can cause volcanoes to erupt. There are different types of eruptions from volcanoes. The type of eruption depends on the magma that is located inside the Earth. There are Hawaain eruptions which consist of a runny lava that flows with ease from the volcano. There are Strombolian eruptions that eject lava and rocks into the air. There are Vulcanian eruptions which are very explosive. It all depends on the viscosity of the magma, and the amount of gas that will determine what type of eruption. Igneous rocks form when the magma or lava cool down. There are two types of igneous rocks. They are either intrusive or extrusive. Extrusive igneous rocks form when the lava cools on the Earth’s surface. Intrusive igneous rocks form when the lava cools beneath the Earth’s surface, in the core of it. There are 6 main types of igneous rocks. They are Rhyolite, Granite, Andesite, Diorite, Basalt and Gabbro. Although these are the most common, there are hundreds of other types. The reason that there are so many different types of igneous rocks is because of fractional crystallization, which is a sort of reversal of fractional melting. Any single magma source can differentiate into different types of magma during this process. During crystallization the last minerals to melt are the first ones to crystallize. The result of crystallization is a rock...
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