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The Volcanic Explosivity Index (VEI) was devised by Chris Newhall of the U.S. Geological Survey and Steve Self at the University of Hawaii in 1982 to provide a relative measure of the explosiveness of volcanic 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 and ranges from 0, for non-explosive eruptions (less than 10⁴ cubic metres of tephra ejected), to 8, for mega-colossal explosive eruptions that can eject (10¹² cubic metres of tephra and a cloud column height of over 25 km). Values higher than 8 can be determined if needed.

One weakness of the VEI is that it does not take into account of the density of erupted material; ash, volcanic bombs, and ignimbrite are all treated alike.

VEI	Classification	Description	Plume height	Volume ejected	How often	Example	Total historic eruptions as of 1994
0	Hawaiian	non-explosive	< 100 m	> 1000 m³	daily	Kilauea	-
1	Hawaiian/ Strombolian	gentle	100-1000 m	> 10,000 m³	daily	Stromboli	-
2	Strombolian/ Vulcanian	explosive	1-5 km	> 1,000,000 m³	weekly	Galeras , 1992	3477
3	Vulcanian	severe	3-15 km	> 10,000,000 m³	yearly	Nevado del Ruiz, 1985	868
4	Vulcanian/ Plinian	cataclysmic	10-25 km	> 0.1 km³	≥ 10 yrs	Galunggung, 1982	278
5	Plinian	paroxysmal	> 25 km	> 1 km³	≥ 100 yrs	St. Helens, 1980	84
6	Plinian/ Ultra-Plinian	colossal	> 25 km	> 10 km³	≥ 100 yrs	Krakatau, 1883	39
7	Ultra-Plinian	super-colossal	> 25 km	> 100 km³	≥ 1000 yrs	Tambora, 1815	4
8	Ultra-Plinian	mega-colossal	> 25 km	> 1000 km³	≥ 10,000 yrs	TobaLake Toba is a large lake, 100km long and 30km wide, in the middle of the northern part of the Indonesian island of Sumatra. Geology In 1949 the Dutch geologist Rein van Bemmelen reported that Lake Toba was surrounded by a layer of ignimbrite rocks, and w, 71 ka	1

Count of historic eruptions based on 1994 figures maintained by the Global Volcanism Program of the Smithsonian InstitutionThe Smithsonian Institution is a museum complex with most of its facilities in Washington D. It consists of 16 museums, 7 research centers and 142 million items in its collections. A monthly magazine published by the Smithsonian Institution is also named

1 See also

Nevado del Ruiz, 19851985 is a common year starting on Tuesday. Events January events January 1 Creation of the Internet's Domain Name System. January 17 British Telecom annouces they are going to abolish the famous red telephone boxes. January 23 A debate in the House of Lor (VEI = 3)
Mount St. Helens, 1980 eruption (VEI = 5)
KrakatoaKrakatoa ( Indonesian name: Krakatau is a volcano on the Indonesian island of Rakata in the Sunda Strait. It has erupted repeatedly, massively and with disastrous consequences throughout recorded history, but the most well known of these events occurred o, 1883 (VEI = 6)
Novarupta, 1912 (VEI = 6)
Mount Tambora, 1815 (VEI = 7)
Long Valley Caldera (VEI = 7)
Yellowstone (VEI = 8)

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Volcanic Explosivity IndexThe Volcanic Explosivity Index (VEI) was devised by Chris Newhall of the U. Geological Survey and Steve Self at the University of Hawaii in 1982 to provide a relative measure of the explosiveness of volcanic eruptions. Volume of products, eruption cloud h	Volcanic ashVolcanic ash is rock particles less than 0. 25 inch across ejected from a volcanic vent. The term for any material explosively thrown out from a vent is ejecta or pyroclastic debris. If liquid magma is ejected as a spray, the particles will solidify in th	Volcanic coneVolcanic cones are among the simplest volcano formations. They are built by fragments (called ejecta thrown up (ejected) from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, d
Volcanic winterA volcanic winter is the reduction in temperature caused by volcanic ash and droplets of sulfuric acid obscuring the sun, usually after a volcanic eruption (hence the name). The explosion of Krakatoa in 1883 precipitated just such a condition; the next fo	Volcanic bombVolcanic bombs are globules of melted rock ( tephra) larger than 2 to 3 inches in diameter that are thrown into the air during a volcanic eruption, cooling into solid fragments before they reach the ground.	Volcanic fieldA volcanic field is a spot of the earth's crust that is prone to localized volcanic activity. The San Francisco volcanic field in Arizona and the Auckland volcanic field in New Zealand are examples of this.
Volcanic arc

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