News blog

Supervolcano? Or just hot air?

MtStHelens.jpg

A paper published in Nature Geoscience this week is causing consternation for other geologists.

The news, already reported on earlier this year when presented at a conference, comes from Graham Hill, at GNS Science in Wellington, New Zealand, and his colleagues.

Hill is claiming that underneath Mount St Helens Mount Adams, and possibly Mount Rainier in the Cascades – a mountain range in Washington State in the US – lurks a giant magma chamber. The initial news story in New Scientist, based on the AGU meeting in June this year, suggested that this meant a supervolcano was waiting to erupt in this region.

Hill’s work, now published, is based on measurements of electrical conductivity in the rocks under the northern Cascades. This, according to Hill confirmed a widespread layer of high conductivity material under the range. The reason they infer a large molten magma chamber is because molten rock has different conductivity than solid rock. This large magma chamber could link Mt St Helens, Mt Adams and Mt Rainier, leading to the supervolcano links.

Cue ruffled feathers: the volcano blog Eruptions wasn’t pleased, nor was the Oregonian. And now the aforementioned paper based on this presentation has been published, they’re at it again.

What was the cause of their displeasure? The author of Eruptions disputes that the magma chambers under this mountain range could all be linked, and he says that the magma down there is not molten, or at least not much of it is. Judging by the comments thread at that blog, others are similarly sceptical.

In the Miami Herald Seth Moran, a volcano seismologist with the USGS Cascades Volcano Observatory in Vancouver, Washington is quoted as saying. “Other geophysical studies don’t support this theory.”

“Moran said the most telling evidence that the theory was wrong was the lack of any surface evidence, such as geothermal vents or hot springs, among the mountains that would indicate the presence of a super-heated underground magma pool,” the piece reads.

Ah, but the Miami Herald piece also asserts that Hill is making no claims about a supervolcano at all. And taking a look at the press release that accompanied the paper, no such bold claims are actually made. It reads: “If confirmed by additional methods, this could be one of most widespread magma-bearing areas of continental crust discovered thus far.”

Over at the Seattle Times, another geologist, George Bergantz from the University of Washington, says that this study is the best yet, and calls the study “provocative” but nevertheless something that warrants further work.

Who is right? I don’t know. But I will definitley be keeping an eye out for responses to the paper.

The paper’s conclusions state that their work “raises the possibility that the entire SWCC [Southern Washington Cascades Conductor, a conductive zone known in this region] marks a single laterally extensive zone of partial melt in the mid-crust.” And ends by saying that more work is needed to prove the point. Well, at least on that point I’m sure everyone will agree.

Image: Mount St Helens, by Steve Schilling, USGS

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