Classification
The VEI associated with an eruption is dependent on how much volcanic material is thrown out, to what height, and how long the eruption lasts; with the indices running from 0 to 8. The scale is logarithmic from VEI 2 and up; an increase of 1 index indicates an eruption that is 10 times as powerful. As such there is a discontinuity in the definition of the VEI between indices 1 and 2. The lower border of the volume of ejecta jumps by a factor of 100 from 10,000 to 1,000,000 m3 (350,000 to 35,000,000 cu ft) while the factor is 10 between all higher indices.
| VEI | Ejecta volume | Classification | Description | Plume | Frequency | Tropospheric injection |
Stratospheric injection |
Examples |
|---|---|---|---|---|---|---|---|---|
| 0 | < 10,000 m³ | Hawaiian | effusive | < 100 m | constant | negligible | none | Kīlauea, Piton de la Fournaise, Erebus |
| 1 | > 10,000 m³ | Hawaiian / Strombolian | gentle | 100–1000 m | daily | minor | none | Stromboli, Nyiragongo (2002) |
| 2 | > 1,000,000 m³ | Strombolian / Vulcanian | explosive | 1–5 km | weekly | moderate | none | Galeras (1993), Mount Sinabung (2010) |
| 3 | > 10,000,000 m³ | Vulcanian / Peléan | severe | 3–15 km | few months | substantial | possible | Nevado del Ruiz (1985), Soufrière Hills (1995) |
| 4 | > 0.1 km³ | Peléan / Plinian | cataclysmic | 10–25 km | ≥ 1 yr | substantial | definite | Mount Pelée (1902), Eyjafjallajökull (2010) |
| 5 | > 1 km³ | Plinian | paroxysmal | 20–35 km | ≥ 10 yrs | substantial | significant | Mount Vesuvius (79 CE), Mount St. Helens (1980) |
| 6 | > 10 km³ | Plinian / Ultra-Plinian | colossal | > 30 km | ≥ 100 yrs | substantial | substantial | Krakatoa (1883), Mount Pinatubo (1991) |
| 7 | > 100 km³ | Ultra-Plinian | super-colossal | > 40 km | ≥ 1,000 yrs | substantial | substantial | Mazama (c. 5600 BCE), Thera (c. 1620 BCE), Tambora (1815) |
| 8 | > 1,000 km³ | Supervolcanic | mega-colossal | > 50 km | ≥ 10,000 yrs | substantial | substantial | Yellowstone (640,000 BP), Toba (74,000 BP) |
A total of 47 eruptions of VEI 8 magnitude or above, ranging in age from Ordovician to Pleistocene, have been identified, of which 42 occurred in the past 36 million years. The most recent is Lake Taupo's Oruanui eruption, 26,500 years ago, which means that there have not been any Holocene (within the last 10,000 years) eruptions with a VEI of 8. There have been at least 5 identified Holocene eruptions with a VEI of 7. There are also 58 plinian eruptions, and 13 caldera-forming eruptions, of large, but unknown magnitudes. There are likely many other eruptions that are not identified.
Read more about this topic: Volcanic Explosivity Index