The volcanic explosivity index (VEI) is a term that has been repeated since a scientific report from the Canary Islands Volcanic Emergency Plan declare the Cumbre Vieja volcano as category 2. This marker allows to compare eruptions of different sizes and explosiveness, as explained Joan Marti, director of Geosciences Barcelona of the CSIC. The researcher details that it is a logarithmic scale, ranging from 0 for non-explosive eruptions to 8 for the largest explosive eruptions identified in the geological record. As you go up this scale, the eruptions have less and less frequency. After 5, the periodicity between them amounts to more than a hundred years. To calculate VEI it is necessary, according to Marti, to measure two parameters: intensity and magnitude. Intensity is “the amount of magma that is expelled per unit of time and is measured at the height of the eruptive column.” This is directly proportional to the explosive capacity of the eruption. The magnitude, on the other hand, counts the total material ejected and is expressed in cubic kilometers.
This index is being criticized by some of the experts. There is even a certain tendency to request the revision of the magnitude parameter, says the CSIC scientist. While the intensity does allow to measure in real value, in the magnitude the results are not so precise: “The question of the total volume thrown does not serve for those small volcanoes in terms of explosiveness, but that throw a lot of magma, which can have few gases, for example ”. A representation of this would be the Hawaiian explosions, which are in the lower volcanic explosive index. These are very large eruptions in terms of the volume of the material thrown and it is given a very low explosiveness, despite the fact that this volume is very high. “There the parameter that we really take into account is the height of the column. Between 0 and 2 that volume correspondence is not so exact ”, he specifies. However, this does not occur from 3 to 8, where there is a direct relationship between the amount of material expelled and explosiveness.
The researcher comments on some examples of volcanoes of different volcanic explosiveness:
VEI 0: Kilauea Volcano in 1975
It is the most active volcano in Hawaii. On November 29, 1975, after a severe earthquake (the largest since 1868), lava erupted for a short time and without causing major problems. The vast majority of Kilauea eruptions have the lowest rate of volcanic explosiveness.
VEI 1: Masaya Volcano in 2008
It is one of the most active volcanoes in Nicaragua. On April 29, 2008, it suffered an eruption of gases and ash in moderate quantities. This expulsion of ash and steam was repeated in June, and from August in the rest of the months of the year, forming dark columns.
VEI 2: Cumbre Vieja Volcano in 2021
On Sunday, September 19, 2021, the volcano on the island of La Palma erupted. Since then the lava has already covered more than 680 hectares and has a perimeter of 36.24 kilometers. Currently it is still in full activity and has forced to restrict the airspace on several occasions.
VEI 3: Nevado del Ruiz Volcano in 1985
Together with the Santa Isabel and Tolima volcanoes, it forms part of the Los Nevados National Natural Park. On November 13, 1985 there was an eruption of explosivity index 3 that was the deadliest in South America with about 25,000 deaths.
VEI 4: Eyjafjallajökull Volcano in 2010
Its name means the glacier on the island’s mountain. On April 14, 2010, the largest Eyjafjallajökull eruption occurred. This has been the first and only time that the volcano has reached 4 in VEI. The ash cloud created forced the cancellation of more than 5,000 flights in Europe.
VEI 5: Mount St. Helena in 1980
After two months of earthquakes and small explosions, on May 18, 1980, Mount St. Helena erupted causing the largest volcanic disaster in the United States. In this catastrophe 57 people died, including a scientist who was studying this phenomenon.
VEI 6: Pinatuvo Volcano in 1991
On June 15, 1991, after months of earthquakes, the volcano erupted with great magnitude. Such was the case that so much magma and rock was removed from the underside of the volcano that its summit collapsed and a 2.5-kilometer-wide slope was created. This natural disaster left more than 850 dead.
VEI 7: Tambora Volcano in 1815
From April 10 to 11, 1815, the Tambora erupted, causing the immediate disappearance of 10,000 people. To this figure we must add 50,000 more people who died from the consequences of this volcano. It also had major climatic effects, with especially frigid temperatures in Europe and the northeastern United States during 1816.
VEI 8: Toba volcano 74,000 years ago
About 74,000 years ago there was the largest known eruption since the Pleistocene. This volcano expelled around 2,500 cubic kilometers of ash and lava. These ashes have been identified in Tanzania, more than 7,000 kilometers away. The climatic consequences are still the subject of debate today.
Infographics: Jorge Moreno Aranda placeholder image