Volcanic eruptions as we know them today have a place in our lore as terrifyingly powerful acts of nature. Gods have been made of them and cultural touchstones built around them. They remain a disaster that we can do nothing to prevent and can only try to avoid. That said, the volcanoes of human recorded history have literally nothing on the volcanoes of earth's past. They are tiny pimples in comparison to the planet-changing, climate-destroying, extinction-event-triggering behemoths we have evidence of in the geologic record. Geologists categorize these monsters as Mega Colossal and the public calls them supervolcanoes. This list captures some of the largest, most powerful explosive eruptions on the planet, not necessarily the largest or the most volume of ejecta. The Deccan traps are not on this list, for example, because they were not explosive in nature despite the fact they erupted for longer and covered more landmass than some of the explosive events.
These eruptions are all classified as VEI 8, the most cataclysmic you can get. Explosive volcanic eruptions are classified using the Volcanic Explosivity Index, or VEI. It is a logarithmic scale, which means that an increase of one in VEI number is equivalent to a tenfold increase in volume of erupted material. The VEI scale does not distinguish between different types of volcanic ejecta ( ash, lava, ignimbrite), only power. On this scale, VEI 8 eruptions are so cataclysmic that they often form deep circular calderas rather than cones because the downward withdrawal of magma causes the overlying rock mass to collapse into the empty magma chamber beneath it. To give a sense of the VEI scale, St. Helens was a 5. This is a list of the largest, most earth-shaking events in the planet's history - best as we can tell. Let's all hope that there are no new VEI 8s to add to this list any time soon.
The boundaries in the imagery with each entry are as approximate as can be determined from the geologic record.
- Photo: Ranker5
4 Million Years Ago
La Pacana Caldera is responsible for the eruption of the giant Atana ignimbrite, which is the fifth-largest explosive eruption known. Atana erupted almost simultaneously with the much smaller Toconao ignimbrite from the same caldera, but it was Atana that formed the caldera. The eruption was still underway when the terrain subsided 1.2–1.9 miles. The Atana flow reached a volume of 588–840 cu miles and 98–131 ft. This flow sheet originally probably covered a surface area of about 3,000 sq miles, part of which was later eroded away.
- Photo: Ranker6
Lava Creek Eruption
630,000 Years Ago
This is the eruption that formed the Yellowstone Caldera itself. The Lava Creek eruption covered much of western central United States. The maximum thickness the volcanic ash reaches is up to 660 feet thick. Given the ash has since compacted due to the weight of overlying sediment, the ash bed deposited would have been thick enough to cover most of our modern skyscrapers. This was a truly catastrophic release of ash into the atmosphere and it had a significant impact on both climate and life. This eruption most certainly sent the world into a volcanic winter. Lava Creek was the last time the Yellowstone Caldera erupted, and it is still sitting down there - waiting - ready to go again. Hopefully not any time soon.
Yellowstone hotspot is called such because of the hotspot that currently sits below it under the crust and one day it will join the ranks of deceased calderas across the Snake River plain. Indeed, it seems to be showing us behavior patterns similiar to the deceased Heise volcanic field in terms of the 'lighter' magma eruptions it has last produced. That said, if it follows Heise's example, it is due for a life-ending final eruption well into the VEI 8 category. Let's hope it isn't using its extinct pal as a role model.
- Photo: Ranker7
1.2 Million Years Ago
Taupo Volcanic Zone
Mangakino is the oldest rhyolitic volcano in the highly volcanic Taupo zone. 10 eruptions have been derived from it alone. One of the largest ignimbrite eruptions of the caldera was the Kidnappers eruption. Kidnappers represents the most wide-spread ignimbrite yet known. The eruption which followed on its heels 200,000 years later was the Ongatiti eruption.
- Photo: Ranker8
Cerro Galán Eruption
2.2 Million Years Ago
Central Andean Volcanic Zone
Located in present day Argentina and considered to be the largest exposed large caldera in the world, Cerro Galán has been active more than once in its lifespan sitting atop the subduction zone between the Nazca and South American plates. There are about half a hundred volcanoes with recent activity in the Central Volcanic Zone. The largest eruption of Galán 2.2 million years ago was the source of the Galán ignimbrite, which covered the surroundings of the caldera with ignimbrite material. The volume of this ignimbrite has been estimated to be about 160 cu miles. There were several other smaller ignimbrite eruptions since and presently two hot springs are active in the caldera.