This is a type of volcano called a stratovolcano. You can see how this very tall volcano has been built up by layers of ash and lava from previous eruptions.
The volcano is currently dormant. But it is about to re-awaken!
Because it is lighter than solid rock, magma (molten rock) has been rising to form a huge pool, called a magma chamber, beneath the volcano.
The volcano will erupt when gases held within the magma burst out explosively, now that they are under less pressure than when the magma was deeper within the earth.