Various factors trigger a volcanic eruption. The three predominant factors are the magma's buoyancy, the pressure from the gases that separate in the magma and the merger of a new batch of magma with a chamber already filled with magma.
The melting of rock inside the earth produces a melt with more volume than the rock but the same mass. This melt is less dense than the rock that surrounds it. The lighter magma moves upward because of its buoyancy, and if the density between the surface and zone of its generation is less than the overlying and surrounding rocks, it erupts.
A few magma compositions contain dissolved volatiles such as water and carbon dioxide. The amount of gases dissolved in the magma is zero at atmospheric pressure, but it increases with an increase in pressure. In andesitic magma, which is saturated with water, the solubility of water decreases as the magma moves upward, and the water separates from it in the form of bubbles. When the volume of bubbles in the magma reaches about 75 percent, disintegration of magma into partially solid and molten fragments happens, along with an explosive eruption. Injection of more magma inside an already filled magma chamber forces some of the magma to move toward the surface, causing an eruption..Learn More
Volcanic eruptions mainly produce steam (H2 0 ), sulfur dioxide (SO 2 ) and carbon dioxide (CO 2 ). They do release other gases in lesser amounts, such as carbon monoxide (CO), helium (He), hydrogen (H 2 ), hydrogen chloride (HCL), hydrogen fluoride (HF) and hydrogen sulfide (H 2 S).Full Answer >
Volcanic eruptions occur when magma builds up beneath the Earth's crust and forces its way to the surface. Natural vents in the crust allow magma passage to the surface, and eruptions occur when the magma that forms is less dense than the material above it, causing it to flow upward. In some cases, this flow is slow and steady, but it can also be rapid and violent.Full Answer >
According to the Oregon State University Department of Geosciences, a volcanic eruption may become violent if pressure builds up inside the volcano for any reason. An explosive eruption is much more dangerous than a steady flow of magma and can spread ash and pyroclastic material over a wide area. The eruption of Mount Saint Helens in 1980 was a textbook example of a violent, explosive volcanic eruption.Full Answer >
The nature of a volcanic eruption is determined by the temperature, viscosity and the amount of dissolved gases in the magma, according to San Diego State University. These factors determine whether an eruption is calm and nonviolent or explosive.Full Answer >