What is meant by extrusive rocks?

Extrusive rocks are formed on the surface of the Earth from lava, which is magma that has emerged from underground. Intrusive rocks are formed from magma that cools and solidifies within the crust of the planet. If lava cools almost instantly, the rocks that form are glassy with no individual crystals, like obsidian.

What are 4 extrusive rocks?

Extrusive igneous rocks erupt onto the surface, where they cool quickly to form small crystals. Some cool so quickly that they form an amorphous glass. These rocks include: andesite, basalt, dacite, obsidian, pumice, rhyolite, scoria, and tuff.

What are extrusive rocks for kids?

Extrusive rocks are formed when magma rises to the surface of the Earth and hardens, which forms extrusive igneous rocks. But with intrusive igneous rocks, they are formed when the magma cools and hardens below the Earth’s surface.

What is an example of extrusive igneous rocks?

Extrusive igneous rocks are rocks that erupt onto the surface resulting in small crystals as the cooling takes place quickly. Basalt, tuff, pumice are examples of extrusive igneous rock.

What is extrusive form?

Extrusive rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff.

What are the properties of extrusive rocks?

Extrusive Rocks. Igneous rocks which form by the crystallization of magma at the surface of the Earth are calledextrusive rocks. They are characterized by fine-grained textures because their rapid cooling at or near the surface did not provide enough time for large crystals to grow.

What are three facts about intrusive igneous rocks?

Because the process of the formation of intrusive igneous rock occurs slowly, these rocks tend to have a grainy texture. Examples of intrusive igneous rock include granite and gabbro. Granite is an intrusive igneous rock used as for making gravestones, statues, and countertops because it is very durable.

What is a fun fact about igneous rocks?

Quick Facts: – About 95\% part of earth’s crust is made up of igneous rock. Even earth’s moon is made up of igneous rock. The lightest rock on the earth, Pumice rock is also an igneous rock. Igneous rocks are helpful in the growth of plants because they contain many minerals which can help a plant to grow.

Is pumice an extrusive igneous rock?

Pumice is composed of highly microvesicular glass pyroclastic with very thin, translucent bubble walls of extrusive igneous rock.

Is andesite an extrusive rock?

Andesite is an extrusive rock intermediate in composition between rhyolite and basalt. Andesite lava is of moderate viscosity and forms thick lava flows and domes. The word andesite is derived from the Andes Mountains in South America, where andesite is common. Andesite is the volcanic equivalent of diorite.

How do you know if a rock is extrusive?

Crystal Size and Texture The most obvious difference between extrusive rocks and intrusive rocks is crystal size. Because extrusive rocks cool quickly, they only have time to form very small crystals such as basalt or none at all. On the other hand, intrusive rocks grow larger crystals because they take longer to cool.

What are extrusive rocks used for?

Explanation: Extrusive igneous rocks form when magma hardens above the earth’s surface. Examples of these include pumice and basalt. Pumice is used in toothpaste and cosmetic products, while basalt is used in the construction of statues and buildings.