Igneous Rock Facts

Do you know what igneous rocks are?

Read on, and we’ll tell you everything you need to know about them.

Perhaps you’ll be the next Geography superstar!

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Igneous Rock Facts for Kids

  • Scientists have identified over 700 different types of igneous rocks.
  • People who study rocks are called geologists.
  • Ninety-five percent of the Earth’s crust is made of igneous rock.
  • They normally contain no fossils.
  • Usually made of two or more minerals
  • They are also known as magmatic rocks.
  • Basalt is an example of a basic extrusive igneous rock.
  • Gabbro is an example of intrusive igneous rock.
  • Scientists can tell the age of igneous rocks by using something called radiometric dating.
  • When magma (lava) rises to the surface cools quickly, it forms extrusive igneous rock.
  • When magma cools and hardens below the Earth’s surface, an intrusive igneous rock forms.
  • The ocean floor is normally made out of basalt rock, which is hard and black, and an extrusive rock of course.
  • The batholiths that we spoke about can be as large as about 97 km across.

What is an igneous rock?

There are three main types of rocks Igneous rock, sedimentary rock, and metamorphic rock.

Igneous rock is formed after it cools down and crystallizes.

The rock comes from magma and is found in volcanos.

Depending on how quickly it cools down, it can form either rhyolite or granite.

How is Igneous Rock Formed?

Granite Rock

Magma (lava) comes out onto the surface of the Earth from volcanoes.

We get Igneous rock when magma cools down and becomes a solid.

The rock can form either above ground or below the surface.

Above the ground – magma cools down quickly and we get rock such as Tuff and Basalt.

Below the ground – magma cools down slowly and we get rock such as Granite

What types of Igneous Rocks are there?

Tuff Rock

Igneous Rock is categorized by how it actually formed.

As we know already, igneous rocks form when it cools and hardens, this can happen underground or on the surface.

The exact location of where the rock forms, determines what type of igneous rock it is.

Get ready to find out about different igneous rocks.

Common types of igneous rocks are:

  • Andesite
  • Basalt
  • Dacite
  • Dolerite
  • Diorite
  • Gabbro
  • Peridotite
  • Nepheline
  • Obsidian
  • Scoria
  • Tuff
  • Volcanic bomb

Why are igneous rocks important?

Scientists can learn so much from studying igneous rocks, which makes them really important. They can learn about the chemical makeup of each rock by studying its composition.

This then allows them to understand the types of temperature and pressure that exist deep in the Earth’s mantle.

Are igneous rocks soft or hard?

Igneous rocks are made from magma and come from deep within the inside of the Earth’s crust. Once it cools down and crystallizes, it is usually very hard and difficult to break.

Extrusive Igneous Rocks

Basalt Rock

When magma rises up to the surface of the Earth and then hardens, we get something called extrusive igneous rock.

This type of rock is almost a bit glassy in texture as they form very, very quickly.

Types of extrusive igneous rocks are pumice and basalt.

Pumice is used in heaps of things like toothpaste, cement, and cosmetic products.

What a strange combination!

Basalt however is used in buildings and statues.

Sometimes extrusive rocks are called volcanic rocks as volcanoes are obviously very important in how they form.

Intrusive Igneous Rocks

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.

These rocks take a long, long time to form because of the way that they are made. They feel very grainy when you touch them.

Intrusive igneous rocks are granite and gabbro. Ever heard of gabbro? If not read on to find out.

Granite is used for making gravestones, statues, and countertops too. Do you have a granite countertop at home? It’s very durable, which means it can take a lot of pressure and wears very well.

Gabbro is an interesting rock that you might like to dig around for! It’s often got lots of gold, chromium, and silver in it. You could sell it to make some pocket money!

Then there are things called Plutons and these are like bodies of intrusive rock that mostly have granite in them.

When intrusive rocks form huge bodies, like those found inside of mountains they are called batholiths.

What are igneous rocks used for?

Igneous rocks are used in many different ways. The stonework in many buildings and statues that you see every day is made from Igneous rocks.

In ancient times Diorite was used for making vases that were then decorated. You can still see many of these amazing designs in museums.

Granite is used in many modern buildings, and maybe in your kitchen, you have a granite worktop—many sculptures like using granite for making statues.

The Giant’s Causeway

The Giant’s Causeway, in Ireland, was made from a lava flow that erupted over 55 million years ago.

The lava cooled, and as it did this it split and formed about 40,000 basalt pillars, which look like humongous stepping stones that reach out into the ocean.

So ace that next Geography test with all this cool information about igneous rocks!

You can do it!