These earthquakes are called intraplate earthquakes, which are sometimes devastating but are infrequent. Volcanic Earthquakes Volcanic earthquakes are defined as earthquakes that occur, or are connected, with volcanic activity. These earthquakes occur in two ways. First, often before an eruption minor seismic activity increases in the vicinity of the volcano. Some kilometres below the volcanic vent, very hot viscous magma moves sluggishly under high steam pressure through a network of veins and arteries from one storage chamber to another. Due to this motion, various parts of the surrounding rock become hotter and more strained as the magma puts them under pressure. These forces fracture the neighbouring rocks, and small or moderate earthquakes relieve the strain. Second, sometimes fault rupture precedes the motion of magma and eruption of lava. The earthquake waves from the rupturing fault may shake up the molten material in the storage reservoir beneath the volcano. This, in turn, disturbs the unstable equilibrium of the magma below the vent, and stimulates local volcanic earthquakes. Induced Earthquakes Some earthquakes are induced; this means that they are triggered by human activity. Examples include: