A common igneous rock that forms the Earth's crust is?
There are three types of rocks: igneous, sedimentary and metamorphic. Among these, igneous rocks are formed when magma (molten rock) from underneath the Earth rises up to the surface, cools down and solidifies. The interior of the Earth is very hot and temperatures are high enough to melt rocks. The surface temperature is very low in comparison and thus allows the molten rocks to cool down and solidify into igneous rocks. One of the most common igneous rocks formed on Earth's surface (and hence called extrusive rock) is basalt. It is a fine-grained rock and is very commonly found on the planet's surface. It makes up most of the oceanic crust and is also found in significant fractions in our continental crust. Some other extrusive rocks are andecite and pumice. If the rocks are formed under the surface of Earth, then they are called intrusive igneous rocks. Some examples of such rocks include granite and diorite.
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