A volcano kind of breaks into pieces every time it has an explosive eruption, since the magma and gases escape with so much force that they blow apart the top of the volcano. Most of the time this just leaves a crater (like a hole) at the top, but sometimes the force of the eruption blasts apart the side of a volcano. The eruption of Mt. St. Helens volcano in the United States in 1980 produced such a ‘lateral blast’. The largest eruptions in the world (‘super eruptions’) eject so much magma that the whole ground collapses, leaving behind a crater that looks like a circular depression in the ground (no mountain is left!). An example of this is the eruption of Toba volcano in Indonesia 74 000 years ago which ejected 2800 cubic kilometres of magma. To give you an idea of how incredibly large that was – 1 cubic kilometre is about 400 times the size of the Great Pyramid of Giza in Egypt!