Types of Igneous Rocks
Igneous rocks are formed when molten rock material lava and magma cools down and solidifies. The word igneous has been derived from the Latin word ignis that means fire. The name is given because these rocks are born of fire. These rocks can be identified by small or large crystals randomly arranged on the surface of the rock. On the basis of cooling rate, there are two different types of igneous rocks. Volcanic Rocks are those that cool quickly and form on the earth’s surface around volcanoes. Plutonic rocks are formed when magma cools down very slowly and these rocks are formed within the crust of the earth.
Quick Facts: –
- There are approximately more than 700 different types of igneous rocks. About 95% of the earth’s crust is made of these rocks.
- There are many mountains that are made out of igneous rocks.
- Obsidian is an extrusive igneous rock. It has a glassy structure with black color.
- Pumice is also a type of these rocks. It is the lightest rock on the earth.
- The rate of cooling determines the texture of a rock. The slower the cooling is, the larger the crystals are.
- Basalt is the most common rock of all the extrusive igneous rocks.
- When magma starts to cool down slowly but then finishes the process quite rapidly, the rock will have large crystals surrounded by a fine grainy mass.
- The resultant rock will have a different type of texture known as the porphyritic texture.
- Most of the igneous rocks have two or more minerals. This is the reason why these rocks have more than two colors.
- Earth’s moon is also made out of igneous rocks.
- These rocks are the source of many important minerals, metals and other building materials.