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The inside of the Earth is very, very hot. Because it is very hot, the rock has melted like ice. It has become liquid, like water. It is always boiling, like water in a kettle. If you have seen the kettle boiling you know that the steam and boiling water try to get out. The very hot melted rock inside the earth also tries to get out. Usually it cannot because the outside of the earth is too thick and strong. But in some places the outside of the earth is thin and weak. Sometimes a crack appears. The hot melted rock pushes up through the crack and bursts through. Steam and gas shoot up into the air and the hot melted lava pours out. Big pieces of rock may be thrown high into the air. After a while the volcano becomes quiet again. The melted lava becomes hard again. Later the same thing happens again and again.
A Crack
The Earth
Melted Rock
Volcanoes
