The Earth is made up of four parts:
The atmosphere: the part that surrounds the globe.
The crust: the continents and the seas.
The mantle: light elements, rocks at very high temperatures.
The core: the middle of the earth where the temperature is too high.
How does a volcano start?
Because of the high temperature, the rock lying in the bottom. The rock that became liquid is called magma. It’ll make its way.
The magma will pass through the mantle, reach the magma chamber, then pass through the chimney to reach the surface and propel itself through a crater. This is the volcano.