New research from an international team of scientists has discovered that supervolcanoes here on Earth can remain active and threatening for thousands of years following an initial super-eruption. That’s great.
Seriously, though, I’m sure a lot of our listeners and viewers are familiar with supervolcanoes here on Earth. After all, we can’t go more than a month or two without someone trying to tell us that Yellowstone is in imminent danger of erupting and wiping out the U.S. farming communities in the midwest with the ash fallout. Yes, that’s a real thing that could happen. It has happened before. In fact, the ash from an eruption of the Long Valley Caldera here in California was found as far away as Nebraska. It’s a huge layer called the Bishop Tuff, and it is all over the western United States. And eruptions from Yellowstone are much larger than Long Valley’s.
So worrying about Yellowstone erupting is a completely legitimate worry, just not a “tomorrow it will happen” worry.
Before we get into this new research, which makes supervolcano eruptions even scarier, let’s talk basics. What makes a volcano “super”? An eruption that contains at least 1,000 cubic kilometers of material. How often does this type of eruption occur? Well, geologically speaking, they’re pretty frequent. But from the perspective of humanity, they’re rare, happening once every 17,000 years or so. The last one occurred over 25,000 years ago in New Zealand. These types of eruptions can cause huge issues, though, affecting climate as well as destroying life and rendering the ground temporarily infertile.
Supervolcanoes can occur over both hotspots like Yellowstone and in subduction zones, such as the one at Lake Toba in Indonesia. That particular eruption occurred about 75,000 years ago and wiped out most of humanity at the time. It also led to a volcanic winter that dropped the worldwide average temperature about 4˚C. The ash from that eruption was found as far away as East Africa.
Now, scientists studying that supervolcano eruption have found that the volcano continued to erupt. They examined minerals such as feldspar and zircon (my personal choice in this year’s Mineral Cup) and analyzed the gas inclusions of argon and helium. Lead author Martin Danišík explains: Using these geochronological data, statistical inference, and thermal modeling, we showed that magma continued to ooze out within the caldera, or deep depression created by the eruption of magma, for 5,000 to 13,000 years after the super-eruption, and then the carapace of solidified left-over magma was pushed upward like a giant turtle shell.
Well, that’s slightly horrifying.
Danišík goes on to further explain: The findings challenged existing knowledge and studying of eruptions, which normally involves looking for liquid magma under a volcano to assess future hazard. We must now consider that eruptions can occur even if no liquid magma is found underneath a volcano – the concept of what is ‘eruptible’ needs to be re-evaluated.
So the initial supervolcano eruption is just the beginning of the threat to life on Earth. Things will not settle down quickly, and more eruptions will lead to more loss of life and land and temperature changes, and just general chaos. And this is why when people get all worked up about Yellowstone, geologists get frustrated. Sure, it’s worrying, but the chances of an eruption happening in our lifetime are slim to none.
As Pamela says, the Universe is trying to kill us. Just not right this second.
Curtin University press release
“Resurgence initiation and subsolidus eruption of cold carapace of warm magma at Toba Caldera, Sumatra,” Adonara E. Mucek et al., 2021 September 3, Communications Earth & Environment