How Do Volcanoes Erupt?

A volcano is a mountain with a hole at the top, and hot melted rock sometimes comes out of it.

This is called an eruption.

Deep under the ground, the rock is so hot that it melts.

The melted rock is called magma, and it is lighter than the solid rock around it.

Because of this, it slowly rises toward the surface.

Gas is also trapped in the magma.

It works like the gas in a bottle of soda.

When the magma rises, the pressure goes down, and the gas expands and pushes the magma out of the volcano.

When magma reaches the surface, we call it lava.

Some volcanoes erupt quietly, and the lava flows slowly down the mountain.

Others explode with a loud noise and send ash high into the sky.

Scientists watch active volcanoes carefully, so they can warn people before an eruption.