So, it turns out that there’s a brand-new supervolcano appearing under New Hampshire, Vermont, and Massachusetts – at least, that’s what the headlines are saying all of a sudden.
Turns out that (surprise surprise) this isn’t true, and this is based off a study that was published late last year, one that explicitly said that we should not expect a new Yellowstone-esque caldera (a large crater left by a volcanic explosion) anytime soon, or even in the future. Here’s what’s actually happening.
A heat glow beneath those three states, first discovered back in the 1970s, was long thought to be the afterglow of a dead, once-upwelling plume of mantle material termed the “Great Meteor”. Using fresh seismic waves to determine what material resided down below, a paper in 2016 concluded that there’s an active, independent upwelling of very hot rock taking place right now.
Although the so-called North Appalachian Anomaly (NAA) was already known about, its high temperature and independence from the Great Meteor came as a surprise. The authors suspected, then, that one day, millions of years from now, there would be baby volcanoes of some sort cropping up in the northeastern United States.
In late-2017, Rutgers University – whose researchers co-authored that 2016 paper – used two years’ worth of data from EarthScope, a massive array of seismic instruments, to better constrain what was beneath New England. They zeroed in on those elevated temperatures in the upper mantle, and their data suggested a ballooning-like shape, characteristic of the top of a mantle plume.
It’s narrow, slow-moving, and based on the lack of surface activity – volcanism or deformation – it’s likely to be geologically young. Eventually, this could lead to an eruption at the surface in perhaps 50 million years, but it’s a small plume compared to others, so we shouldn’t expect anything supervolcanic.
In fact, it may be so small that it will never manage to make volcanoes at the surface. So – what’s with the supervolcano shenanigans then? It’s clearly broken volcanologists’ brains on social media:
Supervolcanoes are defined by the United States Geological Survey (USGS) as those that have at some point erupted more than 1,000 cubic kilometers (240 cubic miles) of fresh volcaniclastic material in a sudden and violent way. When they do so, they leave a huge crater known as a caldera.