What causes a violent volcanic eruption?

What causes a violent volcanic eruption?

The explosiveness of a volcano is determined by the nature of the magma (molten rock) and the ease with which gas may escape from it. As magma rises and pressure is released, gas bubbles (mostly of water vapor and carbon dioxide) develop and rapidly expand, resulting in explosions. The energy released by these blasts can move rocks large distances.

Volcanoes can be divided into two main types: stratovolcano and lahars. A stratovolcano is a tall, steep-sided mountain with a permanent or nearly permanent ice cap at its top. It can be either dormant or active volcanoes. Dormant volcanoes show no signs of activity and have not produced lava in recent memory. Active volcanoes are still producing lava and steam emissions but do not have an active crater lake like those found on some cinder cones. Stratovolcanoes are characterized by relatively thin layers of hardened lava flows called tephra that cover most of their surface. Lava flows are thick deposits of very fluid rock that covers much of a volcano's area when it erupts.

Stratovolcanoes are usually found in areas where there is little room to spread out so they tend to build up around them. This is because gas bubbles rise to the top as molten rock flows down the side of the volcano. Without enough space, this leads to a buildup of gas over time until an explosion is likely.

What causes the most violent eruptions?

An explosive eruption is the most intense form of volcanic explosion, according to volcanology. When pressure is quickly reduced at the vent, enough gas has dissolved under pressure within a viscous magma, causing released lava to aggressively froth into volcanic ash. Explosions can be either sub-aerial or underground.

Sub-aerial explosions create pyroclastic flows that are fast-moving masses of hot gas, rock fragments, and dust that can destroy everything in their path. Underground explosions create volcanic bombs that may fall like rocks, but are typically less destructive than pyroclastic flows. Both types of explosions can also trigger lahars - volcanic mudflows that can carry large trees and even whole buildings with them.

The most violent eruptions occur on islands where the impact of losing the heat from the molten rock beneath the surface of the island is greatly increased. Without this escape route, much of the energy from the volcano would be stored as thermal stress until it was released in an explosion.

On islands, especially small ones, the location of these explosions can often be predicted based on the position of tectonic plates. Islands sit atop major continental plates or smaller microplates, and when they begin to slide toward each other due to the force of gravity, they will eventually reach a point where they touch and stop moving apart.

Which factor determines whether a volcano will have an explosive, violent eruption?

The explosive or effusive nature of the explosion is determined by the viscosity, temperature, and composition of the magma. Silica has an impact on the viscosity of lava as well as the overall morphology of the volcano. Silica molecules make a tight connection, allowing volcanic gases to be trapped and promoting catastrophic volcanic eruptions. Lava that is rich in silica tends to be more viscous and require less heat to become fluid.

Volcanoes with high-silica lavas often experience intense surface explosions called "bombs" that can destroy nearby buildings and kill people hundreds of miles away. These bombs are caused by bubbles of gas that rise to the surface of the lava like bubbles in water. When they reach the top, they expand rapidly, causing the surface of the lava to fracture into small particles that are blown away from the volcano.

Volcanoes that produce low-silica lavas tend to have more moderate explosions that cause much less damage. The difference between these two types of volcanoes can be seen at Vesuvius where explosions are strong but rarely deadly because much of the lava that is ejected does not contain any glass molecules. At St. Helens, explosions are rare but devastating because the lava that is erupted is very viscous and results in large rocks being thrown into the air.

Volcanoes that use carbon dioxide gas as their fuel source do not need lava for an explosion.

About Article Author

Paul Goodman

Paul Goodman is a nature enthusiast and environmentalist. He has a degree in biology and is interested in the field of ecology. Paul loves reading about new discoveries in the field of biology, as well as learning about other environmental topics.

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