A volcano is a large rocky structure on the surface of the Earth. Volcanoes look like hills or mountains but they can be quite dangerous because sometimes hot rocks and gases come spilling out from them. When volcanoes ‘erupt’ like this, they can cause lots of damage to things that are nearby.
But why do volcanoes erupt? And how are they made? If we want to understand how volcanoes work, we need to find out more about the structure of our planet, Earth…
Earth, the planet we live on, is shaped like a ball. The outside part, called the crust, is the bit that we live on. The crust is a bit like a shell made of solid rock. Underneath the crust is a thick layer of melted rocks and gas. This part of our planet is called the mantle and the mixture of melted rocks and gas is called magma. And in the very centre of the Earth is the core, which is made of two super-hot metals – iron and nickel. You can find out more about the structure of the Earth and its layers here.
In some places on the Earth’s crust, there are holes or openings, which go all the way down to the mantle below. A volcano is a hill or mountain with one of these holes inside it. And if you want to see how a volcano is ‘born’, check out this video about Mount St Helens in the United States of America.
As the hot gases and liquid rocks that make up magma bubble about in the mantle, there is a build up of temperature and pressure underneath the Earth’s crust. When the heat and pressure get too high, the magma pushes up through the holes inside volcanoes and come spilling out of the top. We call this a ‘volcanic eruption‘ and we call the magma that comes up to the Earth’s surface ‘lava’.
Volcanoes can be found on land or under the sea. There are about 1,500 active volcanoes on Earth – this means that they sometimes erupt lava. If a volcano doesn’t erupt for 2,000 years, we say it is ‘dormant’ (or sleeping) and not very likely to erupt. If a volcano has been dormant for a long time and is not going to erupt again, we say it is ‘extinct’.
My 7-year-old and I love this cute little cartoon film about volcanoes. And if you enjoyed this post, you might like to read these interesting facts about volcanoes or even have a go at making your own volcano experiment!