In this type of eruption, the magma blasts into the air and breaks apart into pieces called tephra. A good example is the eruption of Washington’s Mount St. Pressure builds up until the gases escape violently and explode. If magma is thick and sticky, gases cannot escape easily. Lava flows rarely kill people because they move slowly enough for people to get out of their way.

A good example is the eruptions at Hawaii’s volcanoes. When this type of magma erupts, it flows out of the volcano. If magma is thin and runny, gases can escape easily from it. Some volcanic eruptions are explosive and others are not. The explosivity of an eruption depends on the composition of the magma. Eventually, some of the magma pushes through vents and fissures to the Earth's surface.

Since it is lighter than the solid rock around it, magma rises and collects in magma chambers. Deep within the Earth it is so hot that some rocks slowly melt and become a thick flowing substance called magma.