Petrology

1989 Edition

Explosive volcaniceruptions—classification

  • George P. L. Walker
Reference work entry
DOI: https://doi.org/10.1007/0-387-30845-8_67
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Most volcanic eruptions are to some extent explosive, and the explosivity index, which is the percentage of pyroclastic material (i.e., volcanic material fragmented and ejected from the vent by volcanic explosions) in the total erupted products is often 100%. The volcanic explosivity index is an informal 0–8 scale of increasing explosivity based on erupted volume, plume height, duration of climactic phase, etc., intended as a useful measure of the likely impact of the eruption on man.

There are several different measures of eruption size: (1) magnitude—the total quantity of pyroclastic products (taken as the equivalent volume of dense rock or magma without voids), for which Tsuya's scale (magnitude 9— ≫100 km3, 8—10 to 100 km3, 7—1 to 10 km3, etc.) is a convenient measure, (2) intensity—the discharge rate of magma plus rock from the vent, and (3) violence—the extent to which dispersal is determined by the translational kinetic energy of the pyroclastic system.

The jet emitted from the...

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© Van Nostrand Reinhold 1989

Authors and Affiliations

  • George P. L. Walker

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