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Volcanic Explosivity Index (VEI)


The VEI has some similarities to both the Richter and Mercalli scales for earthquakes with the magnitude and potential effects of volcanic eruptions being measured on a scale of 0-8.

VEI 0-2 events occur almost every year with some volcanoes showing continuous but gentle activity. Examples of VEI Events 3-8 are shown below. VEI 8 Events are so rare, the last one occured 2 million years ago.


VEI 3Ruiz, Colombia1985
VEI 4Galunggung, Java (Indonesia)1982
VEI 5Mount St Helens, USA1980
VEI 6Krakatoa, Java (Indonesia)1883
VEI 7Tambora, Sunda Is (Indonesia)1815
VEI 8Yellowstone, USA2 Ma BP

MEASURE012345678
General DescriptionNon-explosiveSmallModerateModerate-LargeLargeVery LargeVery LargeVery LargeVery Large
Qualitative DescriptionGentleEffusiveExplosiveSevereViolentTerrificCataclysmicParoxysmalColossal
Volume of Tephra (m3)1x1041x1051x1061x1071x1081x1091x10101x10111x1012
Duration of Blast (hours)<111-61-66-126-12>12>12>12
Cloud Column (km)<0.10.1-11-55-1515-25>25>25>25>25
Troposheric InjectionNegligibleMinorModerateSubstantialSubstantialSubstantialSubstantialSubstantialSubstantial
Stratospehric InjectionNoneNoneNonePossibleDefiniteSignificantSignificantSignificantSignificant
Eruption TypeHawaiianHawaiian/StrombolianStrombolianStrombolian/VulcanianVulcanianVulcanian/PlinianPlinianUltra-PlinianUltra-Plinian
Interval Between Eruptions (years)0-1000-1000-1000-1001-1,000100-10,000100-10,00010,000-100,000>100,000
Fatalities Expected1%3%4%14%36%39%100%100%100%


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