When the next supervolcanic eruption comes around, we might only have a year's warning. As scary as this sounds, this is arguably good news – we have time to evacuate those most at risk, if we know what to look for when one of them is about to blow its top. It is, however, just a single study, and you can't generalize when it comes to these things, so perhaps take this with a pinch of salt or two.
As described in a new study in PLOS ONE, analysis of an ancient supereruption in eastern California has provided volcanologists with a detailed history of the last moments of these monstrous magma-filled beasts. It seems that you can tell a lot from the beautiful patterns hidden within magmatic crystals – including how long it takes for magma to prime itself for a cataclysmic eruption.
After a supervolcano empties its magmatic contents into the sky, it takes a while to refill its magma chamber again – some say this recharge process takes just 500 years, but most say at least tens of thousands of years. When the chamber is full, it slowly builds up pressure. As it sits there, different parts of the magma cool and experience localized changes in pressure, and these environmental fluctuations are chemically recorded in the rims of the crystals that begin to form as a result.
Just before the magma breaches the overlying rock in an eruption, there will be an accelerating drop in pressure as dissolved gas begins escaping from the liquid magma. In line with findings from a previous study focusing on Mount St. Helens, this team found that the crystals from the 760,000-year-old Californian Long Valley Caldera supereruption reveal that, from the end of the chamber’s recharge period to the point of eruption, no more than a year of time passes.
Although this sounds short, this means that when the next supereruption is due to occur somewhere else on Earth, humanity – if it’s lucky – may have a full year to prepare for it.
“Supereruptions have been described as the ultimate geologic hazard,” the team of researchers, from Vanderbilt University and the University of Chicago, write in their paper. “Understanding the potential hazards associated with supereruptions is the ultimate geologic exercise.”
Image in text: One of the 73 quartz crystals used in the study, each measuring about a millimeter across. The various chemical rims can be seen quite clearly in this image. G. Gualda/Vanderbilt University