Questions
What do all volcanoes have in common?
Where does magma come from?
What is a volcanologist?
What Causes Volcanoes
Volcanoes come in many different shapes and sizes, but they all have one thing in common. All volcanoes are formed by hot molten rock called magma. Without magma, there would be no volcanoes.A volcano needs magma to erupt.
Magma forms in Earth's mantle, or middle layer. Gas is often mixed in with the magma. After the gas and magma form, they rise up through the crust.
As molten magma pours up through the crust to the surface, it becomes a volcano. When the magma gets near the surface of Earth, it collects in chambers inside the crust. As more and more magma and gas pour into a chamber, the pressure in the chamber grows because the magma and gas are pressing against the walls of the chamber, trying to get out.
As magma builds up in the chamber inside Earth's crust, the magma and gas get ready to break out and spray.
When the pressure gets too high, the chamber can no longer hold back the magma and gas. They begin to squeeze up through the crust, forcing their way out through weak spots in the crust until they reach the surface. When the magma comes out on the surface, volcanologists give it a different name: lava. As the lava builds up on the surface, the volcano begins to grow.