About 74,000 years ago, in what is now Indonesia, Mount Toba violently erupted. The volcanic explosion sent some 700 cubic miles of magma into the air and deposited an ash layer roughly 6 inches thick over all of South Asia.
The eruption—which was an estimated 100 times larger than the largest in modern times, the 1815 Mount Tambora eruption—altered global climate patterns significantly, likely triggering a period of rapid cooling. The effect on ecosystems around the world was dramatic, and it may have nearly led to the extinction of the human species—some genetic studies suggest that the human population went through a bottleneck around that time, with as few as 1,000 breeding pairs of our ancestors surviving the devastating volcanic winter.
Yesterday, scientists from Vanderbilt University and the University of Chicago published a study in the journal PLoS ONE that has an ominous conclusion. Their findings indicate that the underground magma pools that fuel such supervolcanoes—pancake-shaped reservoirs that are typically 10 to 25 miles in diameter and one half to three miles deep—erupt much more quickly than previously thought. The research team says that once these enormous subterranean magma reservoirs form, they are unlikely to stay dormant for very long—they may be capable of sitting quietly for just thousands or even hundreds of years before erupting.
“Our study suggests that when these exceptionally large magma pools form, they are ephemeral, and cannot exist very long without erupting,” said Guilherme Gualda, the Vanderbilt University professor who directed the study, in a press release. ”The fact that the process of magma body formation occurs in historical time, instead of geological time, completely changes the nature of the problem.”
Hundreds of years may seem like a long time when compared to the length of a human life, but a century is just a blip when viewed in terms of geologic time. Most geologic events—the formation of mountains and the movement of tectonic plates, for example—typically occur on the order of hundreds of thousands or millions of years. So the fact that these underground magma pools can only lay dormant for mere centuries is stunning when viewed in the context of conventional beliefs about geology.
Gualda’s research team arrived at the conclusion by studying Bishop Tuff, a rock formation in eastern California that formed as a result of a supervolcano eruption some 760,000 years ago. Using advanced methods for analyzing the date of magma formation, the researchers concluded that the subterranean reservoir developed sometime between 500 and 3,000 years before the eruption. The resulting event covered more than half of North America with a layer of volcanic ash.
The potential effects of a supervolcano eruption in modern times are truly terrifying to behold. The eruption in Mount Tambora in Indonesia, which produced less than 1 percent of the volume of lava and ash of a supervolcano, caused 1815 to become known as “The Year Without a Summer” in North America and Europe. Volcanic ash suspended in the atmosphere blocked enough sunlight from reaching earth so that crop production was severely interrupted, causing famines and food riots in from Switzerland to China.
If the formation and eruption of giant magma pools capable of producing supervolcanoes truly happens as quickly as indicated in the study, it means we ought to take an entirely different approach in preparing for such cataclysms, the researchers report. Thankfully, it is believed that no magma pools of this size are present on earth at this time. But since they can form and erupt so rapidly, the authors recommend that we continually monitor geologic hot spots to detect the earliest signs of formation.
It might be impossible to prevent such natural disasters, but experts agree that preparation and advance warning are the best bet for mitigating the destruction they might bring. Centuries might be short when viewed in terms of geologic time, but they are long for human civilizations—long enough that, if we knew the location of a massive underground magma pool, we might even be able to intentionally avoid building cities and development in the area above it. This wouldn’t prevent the massive level of damage a supervolcano would bring, but it would reduce the destruction to some degree.