Geology Rocks: Igneous Rocks

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Rocks tell us about the past and are an important resource used in the construction of homes and businesses.

There are three classifications of rocks.

1. igneous
2. metamorphic
3. sedimentary

In this lesson, you will learn about the characteristics and formation of igneous rocks.

Some say igneous rocks have the most exciting formation process because igneous rocks are formed from magma.

Magma is a hot, molten liquid that resides below the earth’s surface. When magma appears outside the earth, it is called lava.

The earth's inside can reach up to 13,000 degrees Fahrenheit! The temperature is so hot that it causes rocks and other materials inside the earth to melt. This melted liquid is magma.

Magma that cools inside the earth is referred to as intrusive igneous rocks. Intrusive igneous rocks, such as granite, have large crystals.

When lava cools and hardens above the earth’s surface, it is called extrusive igneous rock. The crystals in extrusive igneous rocks are much smaller than those in intrusive igneous rocks.

When magma or lava cools, it becomes igneous rock.

Igneous rocks make up most of the earth’s crust. They are characterized as having crystals and being porous. Sometimes, the pores in igneous rocks are large enough to appear as tiny bubbles in the stone.

Extrusive igneous rocks typically have a glassy surface. Examples of igneous rocks include granite, pumice, obsidian, and basalt.

• Have you seen or heard of any of these types of rocks before?

To learn more about how igneous rocks are formed, watch the video below.

Visit Igneous Rocks and click on the green Slide Show button to see examples of igneous rocks.

Now that you know more about igneous rocks, answer the original question in your own words.

• What do rocks have to do with exploding volcanoes and hot lava?

Keep showing off what you have learned in the Got It? section!