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In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens . Such eruptions result when sufficient gas has dissolved under pressure within a viscous magma such that expelled lava violently froths into volcanic ash when pressure is suddenly lowered at the vent.
The volcano built itself up from depth and emerged above the Atlantic Ocean off the coast of Iceland in 1963. Initial hydrovolcanics were highly explosive, but as the volcano grew, rising lava interacted less with water and more with air, until finally Surtseyan activity waned and became more Strombolian. [50]
The Grímsvötn volcano in Iceland is a sub-glacial volcano, located beneath the Vatnajökull ice cap. For a typical sub-glacial eruption, overlying glacial ice is melted by the heat of the volcano below, and the subsequent introduction of meltwater to the volcanic system results in a phreatomagmatic explosion. [12]
Mount Ruang spewed lava and and ash on April 17, seen from Sitaro, North Sulawesi. It also triggered lightning in the ash cloud -- a common phenomenon in powerful volcano eruptions.
A volcano needs a reservoir of molten magma (e.g. a magma chamber), a conduit to allow magma to rise through the crust, and a vent to allow the magma to escape above the surface as lava. The erupted volcanic material (lava and tephra) that is deposited around the vent is known as a volcanic edifice, typically a volcanic cone or mountain. [2] [22]
Effusive eruption of basaltic ʻaʻā lava at Mauna Loa in 1984. There are two major groupings of eruptions: effusive and explosive. [1] Effusive eruption differs from explosive eruption, wherein magma is violently fragmented and rapidly expelled from a volcano.
For an explosion to occur, there must be a rapid, forceful expansion of matter. There are numerous ways this can happen, both naturally and artificially, such as volcanic eruptions, or two objects striking each other at very high speeds, as in an impact event. Explosive volcanic eruptions occur when magma rises from below, it has dissolved gas ...
The volcano was dormant for about half of last century, but rumbled back to life with a series of relatively small eruptions beginning in the 1990s. The government ordered evacuations then, and ...