Volcanos Are Dangerous; They Have Been Worse in The Past, And It Could Happen Again


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Things could have turned out a lot worse!

You may have a persistent low-level fear of violent tectonic activity if you live near a fault line or an active volcano. Mount St. Helens and Vesuvius eruptions provide a glimpse of the Earth's devastating potential, but a new study published in the journal Climate of the Past indicates a volcanic history far more violent than anything we've seen in recorded history.

Along with colleagues, Anders Svensson, Associate Professor in the Niels Bohr Institute's Physics of Ice, Climate, and Earth department, used ice cores to peek into the deep history of Earth's volcanic activity. They discovered 85 significant volcanic eruptions over 60,000 years, 69 of which were larger than the Tambora eruption in 1815, the biggest volcanic explosion in recorded history.

"Sulphate and ash are blasted high into the atmosphere during large volcanic eruptions," Svensson told SYFY WIRE. "The sulphate can reach the stratosphere, where it is dispersed all across the globe."

Some of the sulphate then descends to the ground and, depending on the conditions, freezes. The researchers compared ice cores from Greenland and Antarctica. This step was critical since signs seen in both locations imply eruptions powerful enough to have global consequences. It also allowed them to calibrate and timestamp the eruptions more precisely. They can narrow down an estimated age by identifying a signal in both locations and calculating the annual ice layers between them.

The historical period under investigation by experts dates back to the last glacial period and is used to inform climate models. As ash, sulfates, and carbon dioxide enter the atmosphere, they alter the radiation patterns that reach the Earth's surface, influencing global temperatures. It's not entirely clear what triggered these enormous eruptions, although melting ice could have played a role.

"At the end of the last glacial epoch, the great ice sheets melted, raising sea level by 120 meters. "This made the tectonics unstable, and you let go of the pressure, which most likely resulted in additional volcanism," Svensson explained. "Today, we're melting a lot of ice, but we're hoping for a one-meter rise in sea level this century." It's a different scale, and I don't believe we can claim that rising sea levels are promoting volcanism at this time."

Anders Svensson

That doesn't always imply that we're out of the woods. The ice cores provide a 60,000-year record of activity, which reveals something about the frequency of volcanism in the past.

In the geological record, eruptions on the scale of Tambora occur once or twice every millennium. They don't, on the other hand, follow any form of pattern. What's apparent is that, compared to what we know happened over the last 60,000 years, we've had a pretty moderate type of volcanism during our documented history, and things get considerably worse when we go back further.

"Right now, we're focusing on the Toba eruption, which occurred 74,000 years ago in Sumatra. "With a 150-kilometer-wide crater, it's certainly the largest eruption in the previous one or two million years," Svensson added.

That eruption might have had a huge influence on our species as well as the climate. It's unclear how much of an impact it made, but Svensson and his colleagues plan to figure it out. Greenlandic ice cores date back 120,000 years, while Antarctic ice dates back 800,000. We merely need to locate the narrative of the Toba eruption in the ice.

"We know where to search, and we've identified a few candidates." We'll figure out which one is most likely and calculate how much sulphate we got from it. "Hopefully, if we can get the correct statistics for the sulphate, it will help lead the conversation," Svensson added.

It's not always easy to see the silver lining, but at the very least the planet isn't exploding beneath our feet. Yet.

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Hasanul is a Slate senior editor and the editor of Slate’s culture blog, Brow Beat.

Anchorage, AK

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