Yellowstone supervolcano may deposit ash across the U.S. Northwest, clogging rivers and streams and having an effect on agriculture. How much advance warning might we have?
A new research of quartz crystals from the site of a supervolcano that erupted 760,000 years ago indicate that supervolcanoes may perhaps give us about a year’s warning before they blow. That’s based on a study by scientists at Vanderbilt University in Nashville, Tennessee, published July 20, 2016 in the journal PLOS One.
What is a supervolcano,and what occurs if one erupts? As per the U.S. Geological Survey:
A supervolcano is a volcano that at one point in time erupted more than 1,000 cubic kilometers [240 cubic miles] of deposits.
That’s about enough stuff to fill up Lake Erie – one of the U.S. Great Lakes – twice. Realize they’re speaking of “deposits” – quite simply, ash – here. It’s ash that’s the major problem with supervolcanoes. As an example, studies of the supervocano under Yellowstone National Park indicate the lava from past eruptions never traveled much farther than the park boundaries. The ash would go farther, spreading across an region about 500 miles (800 km) across surrounding Yellowstone (Denver, Colorado, for instance, is about 500 miles from Yellowstone). Research indicate the region inside this circle may see more than 4 inches (10 cm) of ash on the ground. A larger area in the central U.S. would see a shallower covering of ash, which would still clog rivers and streams and impact agriculture.
How much warning would we have for such an eruption? The new Vanderbilt study, suggesting a year of advance warning, is based on the concept that – before a super volcano erupts – a huge amount of magma needs to build up. The build-up takes tens of thousands of years, stated study author Guilherme Gualda, but, once established, these giant magma bodies are unstable features that last for only centuries to few millennia. Gualda explained in a statement:
We have shown that the onset of the process of decompression, which releases the gas bubbles that power the eruption, starts less than a year before eruption.
These scientists studied microscopic quartz crystals in pumice obtained from the Bishop Tuff in eastern California, which is the site of the super-eruption that formed the Long Valley Caldera 760,000 years ago. The researchers examined how long it took distinctive surface rims on the crystals to grow, a factor that earlier studies have indicated are indicative of the lead time before a super volcano erupts. The new study determined that over 70 % of the rim growth times were shorter than one year. The paper described:
Maximum rim growth times span from approximately 1 minute to 35 years, with a median of approximately 4 days. More than 70 percent of rim growth times are less than 1 year, showing that quartz rims have mostly grown in the days to months prior to eruption.
The study indicates that intensifying signals of an impending super-eruption would begin to be felt within a year of eruption, but scientists are not sure what exactly the signs at the surface would be.
One of the 73 quartz crystals used in the analysis. They average about one millimeter in diameter. Image via Guilherme Gualda / Vanderbilt University
Here are a couple of the very large eruptions – such as super-eruptions – that have took place in the recent geological past:
– Oruanui eruption, 26,500 years ago. The Taupo Volcanic Zone in New Zealand is the site of this most recent super-eruption. It also includes deposits from more than a dozen very large eruptions that happened within in the last couple of million years.
– Campi Flegrei eruption in Italy, 40,000 years ago.
– Toba eruption in Sumatra 75,000 years ago.
– Yellowstone in the United States has experienced three super-eruptions over the last two million years.
Gualda stated it appears inevitable that another super-eruption will affect the Earth in the future. But, he stated:
As far as we can determine, none of these places currently house the type of melt-rich, giant magma body needed to produce a super-eruption. However, they are places where super-eruptions have happened in the past so are more likely to happen in the future.
Guilherme Gualda of Vanderbilt was lead author on the new supervolcano study. Image via Vanderbilt.
Final conclusion: A new study indicates that supervolcanoes give about a year’s warning before they strike.
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