Volcanic eruption

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Volcanic eruptions.

A volcanic eruption occurs when hot materials are thrown out of a volcano. Lava, rocks, dust, ash and gas compounds are some of the materials.

Eruptions can come from side branches or from the top of the volcano. Some eruptions are terrible explosions that throw out huge amounts of rock and ash and kill many people. Some are quiet outflows of hot lava. Several more complex types of volcanic eruptions have been described by volcanologists. These are often named after famous volcanoes where that type of eruption has been seen. Some volcanoes may show only one type of eruption during a period of activity, while others may show a range of types in a series.

Volcano explosivity index[change | change source]

The volcanic explosivity index (commonly shortened VEI) is a scale, from 0 to 8, for measuring the strength of eruptions. It is used by the Smithsonian Institution's Global Volcanism Program in assessing the impact of historic and prehistoric lava flows. It operates in a way similar to the Richter scale for earthquakes, in that each interval in value represents a tenfold increasing in magnitude (it is logarithmic). Most volcanic eruptions are of VEIs between 0 and 2.

Volcanic eruptions by VEI index

VEI Plume height Eruptive volume * Eruption type Frequency ** Example
0 <100 m (330 ft) 1,000 m3 (35,300 cu ft) Hawaiian Continuous Kilauea
1 100–1,000 m (300–3,300 ft) 10,000 m3 (353,000 cu ft) Hawaiian/Strombolian Months Stromboli
2 1–5 km (1–3 mi) 1,000,000 m3 (35,300,000 cu ft) Strombolian/Vulcanian Months Galeras (1992)
3 3–15 km (2–9 mi) 10,000,000 m3 (353,000,000 cu ft) Vulcanian Yearly Nevado del Ruiz (1985)
4 10–25 km (6–16 mi) 100,000,000 m3 (0.024 cu mi) Vulcanian/Peléan Few years Eyjafjallajökull (2010)
5 >25 km (16 mi) 1 km3 (0.24 cu mi) Plinian 5–10 years Mount St. Helens (1980)
6 >25 km (16 mi) 10 km3 (2 cu mi) Plinian/Ultra Plinian 1,000 years Krakatoa (1883)
7 >25 km (16 mi) 100 km3 (20 cu mi) Ultra Plinian 10,000 years Tambora (1815)
8 >25 km (16 mi) 1,000 km3 (200 cu mi) Supervolcanic 100,000 years Lake Toba (74 ka)
* This is the minimum eruptive volume necessary for the eruption to be considered within the category.
** Values are a rough estimate. Exceptions occur.
There is a discontinuity between the 2nd and 3rd VEI level; instead of increasing by a magnitude of 10, the value increases by a magnitude of 100 (from 10,000 to 1,000,000).

Types of volcanic eruptions

Related pages[change | change source]