Dead volcanoes, seen throughout the southwestern United States, are evidence of volcanic fields that could wipe out infrastructure and disrupt air travel if new volcanoes erupt, a new study says. And researchers say that could happen at any time.
Over the past 2.58 million years, known as the Quaternary geologic period, some 1,800 volcanoes pockmarked the region straddling Arizona, parts of California, Colorado, Nevada, New Mexico and Utah. If the Pinacate volcanic field in the Mexican state of Sonora is included, the number rises to more than 2,200. Some emerged as recently as 1,000 years ago.
These volcanoes are known as monogenetic, meaning “one life.”
“A monogenetic volcano will erupt once, and that eruption may last several days to several decades, but after that, the volcano is basically dead,” said volcanologist and study co-author Greg Valentine.
He pointed out that more attention is rightly given to Hawaii, the Pacific Northwest and Alaska because they host huge stratovolcanoes such as Mount Rainier and Mount St. Helens, which can erupt many times.
Monogenetic volcanoes have been studied mostly for what they reveal about the Earth far below the surface, according to Valentine, though the scientific community is growing more interested in the hazards they pose.
“Most people are surprised to know that there are so many young volcanoes in the Southwest,” he said.
The paper published by Valentine and his colleagues in the journal Geoscience notes that although the volcanoes examined no longer pose a threat, they may reveal the potential for new eruptions.
“Monogenetic volcanoes tend to occur in areas that we call volcanic fields, and the American Southwest is just dotted with these,” said Valentine, adding that no one knows when or where future eruptions will occur.
He cited as an example Flagstaff, Arizona, which lies within a volcanic field where volcanoes have previously erupted. Albuquerque, New Mexico, also has young volcanoes nearby.
“Two of the most recent eruptions in the Southwest occurred near Flagstaff about 1,000 years ago — one just outside of town and the other on the north rim of the Grand Canyon,” co-author and geologist Michael Ort said. Modern agricultural and social practices would need to be altered to cope with new eruptions, similar to adjustments made by Native Americans of the time, he said.
Most volcanoes in the Southwest are far from metropolitan areas, but eruptions could have far-reaching effects, such as ash plumes that disrupt air traffic or electrical grids. Ort highlighted an eruption that occurred a few thousand years ago near Grants, New Mexico, in an area parallel to the modern Interstate 40 and the Burlington Northern Santa Fe Railroad.
“A similar eruption today would take out one of the most important east-west transportation routes in the country. Several volcanic fields lie along these routes, from the Mojave Desert of California to eastern New Mexico, including the one around Flagstaff,” he said.
The chance of a new eruption within the study area over the next 100 years is about 8 percent, said Valentine. However, this figure does not tell the whole story. The study did not consider volcanoes that are currently underground, or the fact that a single eruption can result in multiple vents spewing magma and causing destruction similar to the recent devastation of Spain’s Canary Islands.
“When you look at the region from the perspective of volcanic hazards, we really have very little information,” Valentine said. “Most of the volcanoes have not been dated, so we don’t know how old they are, except that they likely formed some time within the Quaternary Period. Very few have been studied in detail.”
The study indicated that the frequency of eruptions in the area may resemble that of certain volcanoes in the Pacific Northwest. Both Valentine and Ort believe a new volcano could emerge anywhere in the Southwest at any time.
The researchers said it is difficult to set priorities for assessing potential eruptions due to the dearth of information. “If you’re monitoring volcanic fields in the Southwest, where do you put the instruments? Being able to better answer questions like these is what we’re moving toward,” said Valentine.
Edited by Siân Speakman and Kristen Butler
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