Volcanic Eruption Types
Why do some volcanoes to explode with huge eruptions? Why do other volcanoes pour their lava out with no explosion? It turns out, there are many different volcanic eruption types.
Terrifying Explosions Versus Calm Eruptions
Chemistry! Chemistry is what determines what kind of eruption a volcano will have. The substances found in the magma tell us what will happen. The key ingredient is a mineral called silica. Magma with a high amount of silica explodes with more energy. Whereas magma with little to no silica does not explode very much at all. Instead, they simply release rivers of lava across the landscape. Volcanoes do not typically change their eruption type. Volcanoes that explode will always explode. Meanwhile, those that release their lava in calm flows, will always do so.
Types of Eruptions
Hawaiian eruptions are sometimes called fire fountains. That’s because the explosion can last for hours and days. In this kind of eruption, fluid basaltic lava flies into the air in streams, from vents. This lava is very fluid. It can travel for miles away from the eruption site before cooling and hardening. When it does cool, it forms igneous rock.
Volcanoes in Hawaii are known for these kinds of eruptions, thus the name. The Kilauea volcano, a shield volcano on the Big Island is particularly known for these eruptions.
Picture of Kilauea eruption in Hawaii.
Strombolian eruptions were named for the volcano on the island Stromboli. These kinds of eruptions are usually associated with small lava lakes that build up in the conduits of volcanoes. Although still dangerous, these eruptions are one of the least explosive.
These kinds of eruptions have distinct bursts of lava from the mouth of a magma-filled conduit. Explosions occur every few minutes at regular or irregular intervals. These explosions happen because of the popping of large bubbles of gas that reach the surface. They can reach several hundred meters in height.
This is a strombolian eruption.
Like the Strombolian, the Vulcanian eruptions are named for the Italian island, Vulcano. On this island, there is a small volcano that has this kind of eruption. The Italians used to believe that the vent was above the forge of the Roman smith god Vulcan.
Vulcanian eruptions happen two different ways. One is when a plug of lava in the volcanic conduit falls apart and explodes. The other is when there is a rupture of a lava dome. These eruptions are short and small but the magma is very explosive.
These kinds of explosions are powerful. Material from these explosions travels faster than 800mph. It can rise several kilometers into the air. They result in tephra, ash clouds, and pyroclastic density currents. Vulcanian eruptions can be repetitive and go on for days, months, or even years!
Vulcanian eruption from the Tungurahua Volcano.
Plinian eruptions are the largest and most violent type. The eruption columns are often shaped like a mushroom cloud or an Italian pine tree. Pliny the Younger, a Roman historian, observed these similarities when he saw the eruption of Mount Vesuvius in 79 AD. Thus, the name.
Plinian eruptions happen after the breaking down of gassy magma. They can produce falls of ash, scoria and lava bombs that end up miles away from the volcano. The pyroclastic density currents can destroy entire forests and anything else in its path. The eruption of Mount St.Helens, a composite cone volcano, was such an eruption in 1980. This kind of eruption will empty the magma chamber of a volcano. This leaves a volcano inactive for an indefinite period of time.
Surtseyan eruptions occur when magma or lava interacts explosively with water. They occur when an underwater volcano grows large enough to break the surface. In these eruptions, when water touches hot lava it explodes and creates clouds of ash and steam.
One instance of these eruptions was on the volcanic landform island of Surtsey. This volcano erupted off the south coast of Iceland between 1963 and 1965.
This is a volcanic eruption with a lava flow.
These eruptions often have explosions that create pyroclastic flows. Pelean eruptions are named for the eruption of Mount Pelee in 1902 on the Caribbean island of Martinique. The fluid-like mixture from these eruptions is heavier than air, pouring down slopes at high speeds. They are extremely destructive.