A volcano erupts through the build-up and release of pressure, whether that pressure is of its underlying magma, water or both. This release can be explosive, as it was in the famous eruption of Mt. Vesuvius that destroyed Pompeii, or it can be slow and effusive, as it is in the ongoing formation of the Hawaiian islands.
An eruption that is caused solely by pressures underneath the Earth is a magmatic eruption. In a phreatic eruption, underground water heated by magma forms compressed steam, fracturing and weakening the surrounding rock and ultimately resulting in an violent explosive eruption. A phreatomagmatic eruption is caused by the interaction of magma and water; as the water cools the magma, the resulting stress fractures destabilize the volcano, leading to an eruption.
Explosive eruptions are marked by the violent release of compressed gas, including steam and sulfuric compounds. An effusive eruption, on the other hand, contains little compressed gas and is marked by the gradual flow of lava to the surface. These are two extremes of a sliding scale, with rare Plinian and Ultra Plinian eruptions as the most explosive and continuous Hawaiian eruptions as the least. In general, the more frequent a volcanic eruption is, the less violent and explosive it is.Learn More
Montserrat's Soufriere Hills volcano erupted because the underlying pressures beneath the rock grew too high and exploded. A pyroclastic surge was observed, which is a mixture of hot gas and rock that flows at high speeds down the sides of the blown volcano. The presence of this flow means Montserrat experienced a thick lava flow that was impeded, built up and collapsed into a fast-moving pyroclastic surge.Full Answer >
A volcano is a place where molten rock seeps or erupts from beneath the crust. Most volcanoes develop in the oceans, but some occur on land. When the molten rock, which is called lava, erupts with force, large, cone-shaped mountains form, which are also called volcanoes.Full Answer >
A volcano that has recently erupted and may erupt again soon is categorized as an active volcano. Dormant and extinct are also categories of volcanoes.Full Answer >
The lava from a volcano ranges in temperature from 570 to 2,120 degrees Fahrenheit. In comparison, water boils at 212 F, and a pizza oven is generally 500 to 600 F.Full Answer >