Volcanoes and Earthquakes

A restless planet

The ground under your feet feels solid and still, but deep inside, the Earth is hot and restless. The Earth's hard outer shell, called the crust, is not one solid piece. It is cracked into giant slabs called tectonic plates, like a cracked eggshell. These plates float on top of soft, super-hot rock and move very, very slowly — only a few centimetres each year. When they push, pull or slip against one another, we get volcanoes and earthquakes.

What is a volcano? 🌋

Deep underground, it is so hot that rock melts into a thick, gloopy liquid called magma. Sometimes this magma rises up through a crack in the crust. When it bursts out at the surface, the volcano erupts. The melted rock that flows out is now called lava.

Volcanoes can also throw out ash, hot gases and rocks. When the lava cools, it turns hard and forms new rock. Over many eruptions, this builds up into a tall, cone-shaped mountain. Some volcanoes are active (they can erupt), some are dormant (sleeping), and some are extinct (they will never erupt again).

What is an earthquake?

The tectonic plates do not slide smoothly. Their rough edges get stuck against each other as they push. Pressure builds up and up, like bending a stick. Then suddenly the plates slip and release all that energy at once. The ground shakes — that is an earthquake.

The shaking travels out as waves. A big earthquake can crack roads and damage buildings. Scientists use a tool called a seismometer to detect and measure the waves. This helps them learn how strong an earthquake was.

The Ring of Fire 🔥

Most volcanoes and earthquakes happen at the edges of the plates, where they meet. A huge horseshoe-shaped area around the Pacific Ocean has so many of them that it is nicknamed the "Ring of Fire." Countries like Japan, Indonesia and parts of the USA sit along it.

Are they all bad?

Volcanoes and earthquakes can be dangerous, but they are also part of how our planet works. Volcanic ash makes soil very rich, so crops grow well near old volcanoes. Volcanoes even helped create new land and islands over millions of years. People who live in these areas practise safety drills so they know what to do.

Be an Earth scientist

You can model how an eruption works! With a grown-up, put a small amount of baking soda in a cup, then pour in vinegar with a drop of red food colouring. Watch it fizz and bubble up and over the top — just like frothy lava escaping a volcano. (This is a chemical reaction making gas, not real heat.) You can also feel plate movement by pushing two chocolate bars or sponges together and watching the edges crumple or slip.

To see how volcanoes can build new land for living things, read about Food Chains and Ecosystems. And to learn how rain and rivers slowly shape that land over time, read The Water Cycle Explained.