The Yellowstone Caldera is a supervolcano located below Yellowstone National Park in the Western US. It sits between the states of Wyoming, Montana and Idaho and is constantly monitored by the United States Geological Survey (USGS) due to its capability to inflict disaster on a global scale if a supereruption occurs. The last event of this kind has not happened for more than 630,000 years and any serious eruption in 70,000 – which reportedly makes another supereruption overdue.
Larry Mastin, a USGS Hydrologist, worked with fellow colleague Jacob Lowenstern in 2016 to produce a paper on the ash-fall impacts in the event of another supereruption.
Speaking during a lecture the same year, Dr Mastin revealed how USGS scientists have three previous Yellowstone eruptions on record they can use to predict future incidents.
He said: “There have been three major events identified at Yellowstone in the last two million years.
“The largest was Huckleberry Ridge 2.1 million years ago, a volume of about 2,500 cubic metres of magma.
“Then Mesa Falls 1.3 million years ago and Lava Creek – the second of the two Lava Creek eruptions about 600,000 years ago.
“So these are volumes estimated just from these deposits and not including the tephra-fall deposits that may have been transported over 1,000km (620 miles) in distance.
“The duration of these eruptions is not really well constrained, but the experts are inclined to think they were on maybe days – very rapid – days, maybe weeks at the longest.”
Dr Mastin went on to reveal how findings from the Huckleberry Ridge eruption prove Yellowstone has the power to send ash deposits across the US, as far as California – roughly 1,000 miles away.
He also explained how wind patterns seemed to have little impact, making predicting future events even harder.
He continued: “These eruptions did produce tephra falls – in other words, deposits were produced by tephra and rose buoyantly, drifting downwind during these eruptions.
“We know that from the scattered deposits around the United States.
“But, in fact, in a more recent map of these deposits, we have been able to find them as far west as California, Oregon and even offshore.
“So this adds a real puzzle to this because it is significantly upwind from Yellowstone.
“Even if you look at wind patterns that may have existed in the last few million years, it seems unlikely that the wind pattern would have changed dramatically to send ash deposits that far to the west.”
Dr Mastin also discussed during the same lecture the impacts on the duration of an eruption, should Yellowstone go off again.
He added: “Over a three-day period, the umbrella cloud [would] cover most of the North American continent.
“Then it gradually disperses with wind patterns, so you can look at the tephra deposit in these four different three-day simulations.
“One in January, one in April, one in July and once in October, the pale yellow is one to three millimetres, three to 10, 10 to 30, 30 to 100,100 to 300 and the dark regions are over a metre of ash.
“if you go to a one-week duration, the pattern looks pretty similar and for one month it is fairly the same.
“But as you go to one month, we’re decreasing the average eruption rate, which is weakening the growth of the umbrella cloud.”