Igneous rocks are rocks that are formed by magma.
When magma cools down, it becomes a solid. This can happen below the surface of the Earth or on the surface of the Earth.
The word igneous comes from a word in Latin that means fire.
This word is “ignis.” The reason that the word ignis means fire is because igneous rocks are formed by lava that gets hard and cools down and turns into magma.
Magma is lava that comes out of a volcano. When the lava is in a volcano, it is called lava, but as soon as it leaves the opening of the volcano, it is called magma.
Magma can go into rocks and can cover the surface of an area. Magma has temperatures that get as hot as 700 degrees Celsius to 1300 degrees Celsius.
Magma is made up of different molecules and different atoms that of minerals that have been melted.
When the magma cools down, the atoms and molecules change from a liquid state to a mineral and the mineral grows together forming the magma rock.
The Earth’s crust is made up of a lot of igneous rock. Some scientists believe that the crust is 95% igneous rock.
Since lava can form above or below the surface of the Earth, the crust is made of igneous rock from lava forming below the surface.
When rocks start below the surface, these are called intrusive rocks.
When a rock becomes cooled on the surface of the Earth, it is called an extrusive rock.
When lava is a liquid and it cools into a solid, it is also known as crystallization. The minerals of these rocks get bigger and the crystals grow until they hit into other crystals.
When there is enough crystals that are formed together, they cannot be removed form one another and they form intrusive igneous rocks.
These rocks are coarse-grained crystals which means that they have mineral crystals that help them to form. Sometimes, when people look at intrusive igneous rocks, they can see crystals that have formed. Some of these are different colors such as:
If you look at a rock and you see crystals on it, you are studying a rock that is an intrusive igneous rock.
When lava is hot and it cools down, we know it turns into a solid. When an intrusive igneous rock is formed, the lava cools down very slowly, but with an extrusive igneous rock, the cooling happens very fast.
When you look at an extrusive igneous rock, you do not see any crystals because they are very small. The type of igneous rock that is formed depends on how fast or how slow the lava cooled down.
There are many minerals that help to make up igneous rocks. Some of them include:
There are more than 700 different igneous rocks. Some of these include:
Basalt is a type of igneous rock. When basalt has a lot of heat and a lot of pressure on it, it changes from an igneous rock to a metamorphic rock. When this happens, it is called metamorphism.
Tuff is another form of igneous rock. Tuff is formed when volcanic ash turns to rock.
Granite is an igneous rock that has quartz in it. This kind of rock is very strong, and people use it to help build things.
Pumice is a type of igneous rock that is not very strong. It is formed when molten rock is blown quickly out of a volcano and bubbles are formed.
These bubbles cool down quickly and have hardly any pressure. When this happens, it forms pumice. When you look at pumice, it looks like it has bubbles in it, and it is a rock that is very easy to break.
Obsidian is an igneous rock that is made from volcanic rock that forms quickly and crystals grow on it making it very sharp.
This is also called volcanic glass because it is shiny and looks like glass. This type of rock can be used to make weapons because of how sharp it is.
There are two classifications for igneous rocks that are based on what the rocks are made up of:
Why Are Igneous Rocks Important?
Igneous rocks are important because they help to tell the age of the world. Also, many of the tectonic plates that move are made up of igneous rocks.
Another reason that igneous rocks are important is because many of them have important mineral ores. Some of the mineral ores that are found in igneous rocks include: