A new study appears to provide some good news about supervolcanoes around the world: namely, that in terms of our puny human lifetimes, supereruptions will be signaled well in advance, giving us time to respond as best we can. It must be said, however, that the thought-provoking paper has been viewed more skeptically by some volcanologists.
Before we understand why, though, let’s rewind a little. Supervolcanoes, as defined by the United States Geological Survey (USGS), has at one point erupted more than 1,000 cubic kilometers (240 cubic miles) of fresh volcaniclastic material. Ignoring slow profusions of lava termed “flood basalts”, producing this amount of material tends to happen quickly and violently – and leaves behind a huge pit termed a caldera.
There are a few of these geological giants scattered all over the planet, all in various states of (in)activity. You’ve got Yellowstone caldera, of course – a rather infamous one whose next eruption, if it ever happens, will almost certainly be a lava flow, not anything more apocalyptic. You’ve also got Campi Flegrei in Italy, and Taupo on New Zealand’s North Island.
Each is idiosyncratic. Highly complex, individualistic magmatic systems and tectonic settings, combined with only a handful of supereruptions preserved in the geological record, mean that working out how they’ll behave in the future is anything but easy. Similarly, comparing them to each other is an unenviable task.
IFLScience regular Dr Janine Krippner, a volcanologist at Concord University, told us you cannot make sweeping assumptions or approximations. “You cannot generalize volcanoes as each one is different. You have to understand the specific history of the volcano of interest.”
This applies to the prediction of future supervolcanic eruption behavior too. As aforementioned, a massive paroxysm isn’t the only way these calderas can behave, but for some of them, it’s still possible. To wit, a team of geoscientists led by the University of Illinois have looked to the Taupo Volcanic Zone (TVZ) in order to explore how this supervolcano – and perhaps others – behave leading up to a supereruption.
Using historical and current geological data, as well as a 3D numerical model that probed the structural and geophysical characteristics of Taupo, their Geophysical Research Letters paper makes some genuinely interesting conclusions.
Firstly, they note that the magma reservoirs beneath supervolcanoes remain “stable” for most of their lifetimes; the magma reservoir is kept trapped by the overlying crustal rock, and it likely exists in an only slightly molten, mush-like state, with the occasional addition of new magma.
Then, through tectonic stresses – extensional (stretching) especially – the rocky roof of the reservoir quickly fractures and weakens. Combine this with a suitable influx of magma and you’ve got an eruptible melt waiting to violently decompress and rush out.
As the system primes for a blast, you’d see plenty of seismic activity and topographical uplift – clear warning signs. Crucially, the team’s models suggest that this rejuvenation-to-supereruption process will take hundreds or thousands of years to occur.
Geologically, that’s a mere blink, but for humans, that’s plenty of time to be forewarned. (This isn't really emphasized in the paper, but it is in the accompanying press release.)
TVZ is incredibly complex, though – just like all other supervolcanoes. You only need to look at the weird inflation-deflation “breathing” that happens at Campi Flegrei, and not TVZ, to see just how incomparable caldera systems are. Although the team's model is necessarily simple, you probably can’t generalise like this.
Volcanologist Brad Scott, a member of New Zealand’s GNS Science group, told IFLScience that “most volcanologists will say that volcanoes are individuals and should be treated as such.” Saying that, he also opined that this “doesn’t stop one looking at lessons from another and testing to see if they apply.”
Some experts are skeptical. Speaking to the New Zealand Herald, volcanologist Professor Colin Wilson of Victoria University points out that only two eruptive events at TVZ were analyzed. In the last 26,000 years, there have been 28 significant (if not supervolcanic) events, separated by decades, centuries, or millennia.
Even then, tectonic stresses – although definitely playing a role – are just one factor at play. In fact, the more chaotic nature of TVZ’s eruption history suggests that it’s not the controlling factor.
The study’s lead author, doctoral student Haley Cabaniss at Illinois, explained to IFLScience that although there’s plenty to discuss, it's important to remember that the paper's “presented models are a first order approximation of a really complex problem.” These concerns – including the absence of smaller eruptions, which her team saw as inapplicable for this early-stage work – will be addressed in the future, using this paper as a stepping stone.
It can't be emphasized enough that regardless of its merits, this is still just a single study. Others suggest entirely the opposite, in that supervolcanic systems take as short as a few months to a year to transform from sleeping dragon to fiery monster.
The crux of the matter is that there's a lot more work that's needed to be done before we can say one way or the other.