Frequency of Volcanic Eruptions - John Seach

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The volcanic explosivity index is a scale from 1 to 8  to measure the magnitude (erupted volume) and intensity
(eruption column height) of an eruption.
The VEI is not used to describe eruptions of lava which are non explosive.
Ancient eruptions are determined by the volume of deposits.
Modern eruptions are determined by the observed column height.

About 50-60 volcanoes erupt every year.
20-30 are effusive (lava flows), 20-30 are explosive.

360 volcanoes erupted in the 20th century.

Volcanic Explosivity 
Index

Column
Height (km)

Tephra m3

Examples

Eruption Frequency

non explosive

<0.1

104

Kilauea

20-30 such eruptions per year

1

0.1-1.0

106

Yasur
Stromboli
Semeru

VEI 1 eruptions
occur every day
somewhere in the world

2

1-5

107

Usu 2000

VEI 2 eruptions
occur weekly
somewhere on earth

3

3-15

108

Lopevi 2001
Mayon 2001
Cleveland 2001
Tungurahua 2001
Pago 2002

3 per year

4

10-25

109

Galunggung 1982
Rabaul 1994
Augustine 1986
Lamington 1951
Ambrym 1950-51
Shishaldin 1999

1 per year

5

>25

1010

Chaitén 2008
Vesuvius 79 AD

Mt St Helens 1980
Hudson 1991
Fuji 1707-08

1 every 10 years

6

-

1011

Krakatau 1883
Pinatubo 1991
Ambrym 50 AD
Katmai 1912

1 every 100 years

7

-

1012

Tambora 1815

1 every 1000 yr

8

-

1013

Yellowstone

1 every 10 million yr

 

Another measure of an eruption is the Destructiveness Index.
This is the logarithm of the area covered by pyroclastic flows or covered in tephra.

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