volcanic explosivity index 

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. TheVolcanic Explosivity Index (VEI) was devised byChris Newhall of theUS Geological Survey and Stephen Self at theUniversity of Hawaii in 1982 to provide a relative measure of the explosiveness ofvolcanic eruptions.

volcanic explosivity index
eg

VEIVolcano (eruption)
Year
Casualties
Notes
4? La Soufrière 1 19021,680
4 Mount Pelée 2 190233,000 Deadliest eruptionof the 20th century.
6? Santa María 3 19026,000
4 Grímsvötn 4 1903
P Mount Lolobau 5 1904
5 Ksudach 6 1907
4 Mount Lolobau 7 1911
6 Novarupta 8 1912Largest eruption of the 20th century.
5 Colima 9 1913
4 Sakurajima 10 1914
4 Tungurahua 11 1916
4 Agrihan 12 1917
4+ Katla 13 1918
4 Kelud 14 19195000
4 Manam 15 1919
4 Raikoke 16 1924
4? Iriomotejima 17 1924Underwater volcano.
4 Avachinsky 18 1926
4 Komagatake 19 1929
4 Kliuchevskoi 20 1931
4 Mount Aniakchak 21 1931
4 Volcan De Fuego 22 1932
5+ Cerro Azul 23 1932
5 Kharimkotan 24 1933
4 Suoh 25 1933
4? Kuchinoerabujima 26 1933
4? Rabaul 27 1937
4 Parícutin 28 1943–1952
4 Avachinsky 29 1945
4 Sarychev Peak 30 1946
4 Hekla 31 1947
4+ Ambrym 32 1950
4 Mount Lamington 33 19512,942
4 Kelud 34 1951
4 Bagana 35 1952
4 Mount Spurr 36 1953
4 Carran-Los Venados 37 1955
5 Bezymianny 38 1955-1957
5 Mount Agung 39 19631,584
4+ Shiveluch 40 1964
4 Taal 41 1965
4 Kelud 42 1966
4 Mount Awu 43 1966
4 Fernandina 44 1968
4 Tiatia 45 1973
4 Volcan De Fuego 46 1974
4 Tolbachik 47 1975
4 Mount Augustine 48 1976
5 Mount St. Helens 49 198057

volcanic explosivity index by vickyjeet September 2, 2013