The Sierra Nevada mountains are made from: A) Mafic igneous intrusive rock B) Felsic igneous extrusive rock C) Felsic igneous intrusive rock D) Mafic igneous extrusive rock

Answer: C) Felsic igneous intrusive rock

The Sierra Nevada mountains are primarily composed of felsic igneous intrusive rocks, such as granite. These types of rocks are formed when magma cools and solidifies slowly beneath the Earth's surface, which allows for the growth of large crystals. The granite in the Sierra Nevada is known for its large crystals of feldspar, quartz, and mica, which is characteristic of felsic igneous intrusive rocks.

Extra: The composition of igneous rocks is categorized based on the amount of silica content. Mafic rocks are rich in magnesium and iron and have lower silica content, while felsic rocks are rich in elements like silicon and oxygen which contribute to higher silica content. The term "felsic" is a combination of "feldspar" and "silica," indicating the high percentage of these components.

Intrusive rocks, also known as plutonic rocks, form underground at greater depths. This allows them to cool slowly over time, which results in the formation of large, visible crystals. Granite is a classic example of a felsic intrusive igneous rock and is widespread in continental crust, which forms much of the mountain ranges such as the Sierra Nevada.

Extrusive rocks, on the other hand, are formed from magma that erupts onto the surface where it cools rapidly. This fast cooling does not allow for large crystal growth, so extrusive rocks usually have a much finer-grained texture. Examples of extrusive rocks include basalt (mafic) and rhyolite (felsic).

In the case of the Sierra Nevada mountains, the granitic plutons that make up the core of the range were emplaced during the Jurassic to Cretaceous periods, and they represent the cooled, solidified roots of ancient volcanic mountains that have long since eroded away.