Volcanoes are openings in the Earth's crust.
When they erupt they let out gas, ash and melted rock.
The melted rock is called lava.
There are different kinds of volcanoes.
They are usually found where tectonic plates meet.
Hot lava flowing down the side of an erupting volcano. Getty Images
Liquid magma is called lava when it pours out of a volcano. Getty Images
When a volcano erupts
An exploding volcano throws lava, gas and ash into the air. The liquid magma, which is melted rock, starts its journey upwards through the volcano from a magma chamber, or lake, deep inside the earth.
Magma is hot fluid melted rock below the earth's crust.
Magma reaches the surface through the vertical main pipe of a volcano. It is forced up by pressure from deep inside the earth. When it comes out of the earth's surface it is called lava.
The lava pours out of the hole or vent, at the surface of the volcano. A vent can be at the top or sides of a volcano.
Diagram of inside an erupting volcano. ©Jupiter
Different kinds of volcano
Mayon volcano in the Philippines is a cone volcano
Cone volcano
A cone volcano is made up of layers of hardened lava and ash, built up each time the volcano erupts.
Cone volcanoes are triangle-shaped and most have one crater at the top.
Taal volcano in the Philippines is a crater volcano
Crater volcano
A crater volcano is formed when a cone volcano collapses into the magma chamber, forming a caldera. When the volcano next erupts a new cone is formed, in the middle of the caldera. Sometimes, the caldera fills with water, forming a caldera lake.
Shield volcano
Erta Ale is a shield volcano in Ethiopia (Africa) Getty Images
Another kind of volcano is a shield volcano, which is built almost entirely of fluid lava flows. Flow after flow pours out of the volcano's vent or vents in all directions, to build a broad, gently sloping cone.
From the side the volcano looks like a warrior's shield, which is how it got the name.
Other interesting facts
There are volcanoes under the ocean and under the icecaps.
They can also form in hotspots on Earth. Hawaii is an example of a hotspot.
Watch a video:
Explore geography games on volcanoes at NeoK12
It is always a good idea to use more than one source of information, so here are some others for you to investigate
Read more about different kinds of volcano:
http://pubs.usgs.gov/gip/volc/types.html
Read a list of the world's volcanoes arranged in height from tallest to smallest
https://en.wikipedia.org/wiki/List_of_volcanoes_by_elevation
