Chapter 25, Problem 12RQ

What are the most common igneous rocks, and where do they generally occur?

To determine

The most common igneous rocks and where do they generally occur.

Answer to Problem 12RQ

The most common igneous rocks are andesite and granite and they are generally formed on or below Earth’s surface.

Explanation of Solution

Magma is made from the rocks and minerals that are melted and the quality or types can be classified on the basis of the presence of silica in it. All magma forms through melting of pre-existing rock. It occurs in three basic types that are basaltic, andesitic and granitic.

When andesitic magma solidifies, it is known as andesite rock. And when granitic magma cools and solidifies it is known as granite rock. They are formed at a place where the magma cools which can be on or below the Earth’s surface.

Conclusion:

Therefore, the most common igneous rocks are andesite and granite and they are generally formed on or below Earth’s surface.