Volcanic Explosivity Index
Encyclopedia
The Volcanic Explosivity Index (VEI) was devised by Chris Newhall
Christopher G. Newhall
Christopher G. Newhall is a world renowned volcanologist, formerly with the U.S. Geological Survey and since 2008 at the . He is the co-creator of the Volcanic explosivity index and is considered among the worlds leading experts in volcanic prediction.-Life:...

 of the U.S. Geological Survey and Stephen Self at the University of Hawaii
University of Hawaii at Manoa
The University of Hawaii at Mānoa is a public, co-educational university and is the flagship campus of the greater University of Hawaii system...

 in 1982 to provide a relative measure of the explosiveness of volcanic
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

 eruptions.

Volume of products, eruption cloud height, and qualitative observations (using terms ranging from "gentle" to "mega-colossal") are used to determine the explosivity value. The scale is open-ended with the largest volcanoes in history given magnitude 8. A value of 0 is given for non-explosive eruptions, defined as less than 10000 m³ (353,146.7 cu ft) of tephra
Tephra
200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....

 ejected; and 8 representing a mega-colossal explosive eruption that can eject 1000000000000 m³ (35,314,666,212,661.3 cu ft) of tephra
Tephra
200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....

 and have a cloud column height of over 50 km (31.1 mi). The scale is logarithmic, with each interval on the scale representing a tenfold increase in observed eruption criteria (exception: between VEI 0 and VEI 1).

Note that ash
Volcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...

, volcanic bomb
Volcanic bomb
A volcanic bomb is a mass of molten rock larger than 65 mm in diameter, formed when a volcano ejects viscous fragments of lava during an eruption. They cool into solid fragments before they reach the ground. Because volcanic bombs cool after they leave the volcano, they do not have grains...

s, and ignimbrite
Ignimbrite
An ignimbrite is the deposit of a pyroclastic density current, or pyroclastic flow, a hot suspension of particles and gases that flows rapidly from a volcano, driven by a greater density than the surrounding atmosphere....

 are all treated alike. Density and vesicularity (gas bubbling) of the volcanic products in question is not taken into account. In contrast, the DRE (Dense-Rock Equivalent
Dense-rock equivalent
Dense-rock equivalent is a volcanologic calculation used to estimate volcanic eruption volume. One of the widely accepted measures of the size of a historic or prehistoric eruption is the volume of magma ejected as pumice and volcanic ash, known as tephra during an explosive phase of the eruption,...

) is sometimes calculated to give the actual amount of magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...

 erupted. Another weakness of the VEI is that it does not take into account the power output of an eruption, which makes it extremely difficult to determine with prehistoric or unobserved eruptions.

Classification

Scientists indicate how powerful volcanic eruptions are using the VEI. It records how much volcanic material is thrown out, to what height, and how long the eruption lasts; the scale goes from 0 to 8. The scale is logarithmic; an increase of 1 indicates an eruption that is 10 times more powerful.

Note: There is a discontinuity in the definition of the VEI between indices 1 and 2. The lower border of the volume of ejecta jumps by a factor of 100 from 10000 to 1000000 m³ (353,146.7 to 35,314,666.2 cuft) while the factor is 10 between all higher indices.
VEI Ejecta volume Classification Description Plume Frequency Examples Occurrences in last 10,000 years*
0 < 10,000 m³ Hawaiian
Hawaiian eruption
A Hawaiian eruption is a type of volcanic eruption where lava flows from the vent in a relative gentle, low level eruption, so called because it is characteristic of Hawaiian volcanoes. Typically they are effusive eruptions, with basaltic magmas of low viscosity, low content of gases, and high...

 
effusive < 100 m constant Kilauea
Kilauea
Kīlauea is a volcano in the Hawaiian Islands, and one of five shield volcanoes that together form the island of Hawaii. Kīlauea means "spewing" or "much spreading" in the Hawaiian language, referring to its frequent outpouring of lava. The Puu Ōō cone has been continuously erupting in the eastern...

, Piton de la Fournaise
Piton de la Fournaise
Piton de la Fournaise : "Peak of the Furnace" is a shield volcano on the eastern side of Réunion island in the Indian Ocean. It is currently one of the most active volcanoes in the world, along with Kīlauea in the Hawaiian Islands , Stromboli, Etna and Mount Erebus in Antarctica...

 
many
1 > 10,000 m³ Hawaiian/Strombolian
Strombolian eruption
Strombolian eruptions are relatively low-level volcanic eruptions, named after the Italian volcano Stromboli, where such eruptions consist of ejection of incandescent cinder, lapilli and lava bombs to altitudes of tens to hundreds of meters...

 
gentle 100–1000 m daily Stromboli
Stromboli
Stromboli is a small island in the Tyrrhenian Sea, off the north coast of Sicily, containing one of the three active volcanoes in Italy. It is one of the eight Aeolian Islands, a volcanic arc north of Sicily. This name is a corruption of the Ancient Greek name Strongulē which was given to it...

, Nyiragongo (2002)
many
2 > 1,000,000 m³ Strombolian/Vulcanian
Vulcanian eruption
The term Vulcanian was first used by Giuseppe Mercalli, witnessing the 1888-1890 eruptions on the island of Vulcano. His description of the eruption style is now used all over the world for eruptions characterised by a dense cloud of ash-laden gas exploding from the crater and rising high above the...

 
explosive 1–5 km weekly Galeras
Galeras
Galeras is an Andean stratovolcano in the Colombian department of Nariño, near the departmental capital Pasto. Its summit rises above sea level. It has erupted frequently since the Spanish conquest, with its first historical eruption being recorded on December 7, 1580...

 (1993), Mount Sinabung (2010)
3477*
3 > 10,000,000 m³ Vulcanian/Peléan
Pelean eruption
Peléan eruptions are a type of volcanic eruption. They can occur when viscous magma, typically of rhyolitic or andesitic type, is involved, and share some similarities with Vulcanian eruptions. The most important characteristics of a Peléan eruption is the presence of a glowing avalanche of hot...

 
severe 3–15 km few months Nevado del Ruiz
Nevado del Ruiz
The Nevado del Ruiz, also known as La Mesa de Herveo or Kumanday in the language of the local pre-Columbian indigenous people, is a volcano located on the border of the departments of Caldas and Tolima in Colombia, about west of the capital city Bogotá. It is a stratovolcano, composed of many...

 (1985), Soufrière Hills
Soufrière Hills
The Soufrière Hills volcano is an active complex stratovolcano with many lava domes forming its summit on the Caribbean island of Montserrat. After a long period of dormancy, it became active in 1995, and has continued to erupt ever since...

 (1995)
868
4 > 0.1 km³ Peléan
Pelean eruption
Peléan eruptions are a type of volcanic eruption. They can occur when viscous magma, typically of rhyolitic or andesitic type, is involved, and share some similarities with Vulcanian eruptions. The most important characteristics of a Peléan eruption is the presence of a glowing avalanche of hot...

/Plinian
cataclysmic 10–25 km ≥ 1 yr Mount Pelée
Mount Pelée
Mount Pelée is an active volcano at the northern end of the island and French overseas department of Martinique in the Lesser Antilles island arc of the Caribbean. Its volcanic cone is composed of layers of volcanic ash and hardened lava....

 (1902), Eyjafjallajökull
Eyjafjallajökull
Eyjafjallajökull is one of the smaller ice caps of Iceland, situated to the north of Skógar and to the west of Mýrdalsjökull. The ice cap covers the caldera of a volcano with a summit elevation of . The volcano has erupted relatively frequently since the last glacial period, most recently in...

 (2010)
421
5 > 1 km³ Plinian
Plinian eruption
Plinian eruptions, also known as 'Vesuvian eruptions', are volcanic eruptions marked by their similarity to the eruption of Mount Vesuvius in AD 79 ....

 
paroxysmal 20–35 km ≥ 10 yrs Mount Vesuvius
Mount Vesuvius
Mount Vesuvius is a stratovolcano in the Gulf of Naples, Italy, about east of Naples and a short distance from the shore. It is the only volcano on the European mainland to have erupted within the last hundred years, although it is not currently erupting...

 (79 CE), Mount St. Helens
1980 eruption of Mount St. Helens
The 1980 eruption of Mount St. Helens, a stratovolcano located in Washington state, in the United States, was a major volcanic eruption. The eruption was the only significant one to occur in the contiguous 48 U.S. states since the 1915 eruption of Lassen Peak in California...

 (1980)
166
6 > 10 km³ Plinian/Ultra-Plinian colossal > 30 km ≥ 100 yrs Krakatoa
Krakatoa
Krakatoa is a volcanic island made of a'a lava in the Sunda Strait between the islands of Java and Sumatra in Indonesia. The name is used for the island group, the main island , and the volcano as a whole. The island exploded in 1883, killing approximately 40,000 people, although some estimates...

 (1883), Mount Pinatubo
Mount Pinatubo
Mount Pinatubo is an active stratovolcano located on the island of Luzon, near the tripoint of the Philippine provinces of Zambales, Tarlac, and Pampanga. It is located in the Tri-Cabusilan Mountain range separating the west coast of Luzon from the central plains, and is west of the dormant and...

 (1991)
51
7 > 100 km³ Ultra-Plinian super-colossal > 40 km ≥ 1,000 yrs Thera
Santorini
Santorini , officially Thira , is an island located in the southern Aegean Sea, about southeast from Greece's mainland. It is the largest island of a small, circular archipelago which bears the same name and is the remnant of a volcanic caldera...

 (Minoan Eruption), Tambora
Mount Tambora
Mount Tambora is an active stratovolcano, also known as a composite volcano, on the island of Sumbawa, Indonesia. Sumbawa is flanked both to the north and south by oceanic crust, and Tambora was formed by the active subduction zone beneath it. This raised Mount Tambora as high as , making it...

 (1815)
5 (+2 suspected)
8 > 1,000 km³ Supervolcanic mega-colossal > 50 km ≥ 10,000 yrs Yellowstone
Yellowstone Caldera
The Yellowstone Caldera is the volcanic caldera located in Yellowstone National Park in the United States, sometimes referred to as the Yellowstone Supervolcano. The caldera is located in the northwest corner of Wyoming, in which the vast majority of the park is contained. The major features of...

 (640,000 BP
Before Present
Before Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...

), Toba
Lake Toba
Lake Toba is a lake and supervolcano. The lake is 100 kilometres long and 30 kilometres wide, and 505 metres at its deepest point. Located in the middle of the northern part of the Indonesian island of Sumatra with a surface elevation of about , the lake stretches from to...

 (74,000 BP
Before Present
Before Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...

)
0


*Count of VEI 2 and VEI 3 eruptions in the last 10,000 years are based on 1994 figures maintained by the Global Volcanism Program
Global Volcanism Program
The Smithsonian Institution's Global Volcanism Program documents Earth's volcanoes and their eruptive history over the past 10,000 years. The GVP reports on current eruptions from around the world as well as maintaining a database repository on active volcanoes and their eruptions. In this way, a...

 of the Smithsonian Institution
Smithsonian Institution
The Smithsonian Institution is an educational and research institute and associated museum complex, administered and funded by the government of the United States and by funds from its endowment, contributions, and profits from its retail operations, concessions, licensing activities, and magazines...

. Count of eruptions greater than VEI 3 in the last 10,000 years are based on its 2010 figures. There are also 58 plinian eruptions, and 13 caldera-forming eruptions, of large, but unknown magnitudes.


A total of 47 eruptions of VEI 8 magnitude or above, ranging in age from Ordovician
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

 to Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

, have been identified, of which 42 occurred in the past 36 million years. The most recent is Lake Taupo's Oruanui eruption
Oruanui eruption
The Oruanui eruption of New Zealand's Taupo Volcano was the world's largest known eruption in the past 70,000 years, with a Volcanic Explosivity Index of 8...

, 26,500 years ago, which means that there have not been any Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...

 (within the last 10,000 years) eruptions with a VEI of 8.

List of eruptions


External links

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