Examining the 1,800-plus 'young' volcanoesin the US Southwest3 November 2021, by Charlotte Hsu

A view of the crater of Dotsero volcano, a monogeneticvolcano that erupted in Colorado about 4,000 years ago.Credit: Greg Valentine

They're born. They live once, erupting for a periodthat might last for days, years or decades. Then,they go dark and die.

This narrative describes the life of a monogeneticvolcano, a type of volcanic hazard that can poseimportant dangers despite an ephemeralexistence.

The landscape of the southwestern U.S. is heavilyscarred by past eruptions of such volcanoes, and anew study marks a step toward understandingfuture risks for the region.

The research, which will be published on Nov. 2 inthe journal Geosphere, provides a broad overviewof what we know—and don't know—about this typeof volcanism in the U.S. Southwest over the past2.58 million years, a geologic period known as theQuaternary.

During this time, more than 1,800 monogeneticvolcanoes erupted in the region, according to a

count covering Nevada, Utah, Arizona, Colorado,New Mexico and parts of California's eastern edge.Add in the Pinacate volcanic field, located mostly inthe Mexican state of Sonora, bordering Arizona,and the number goes up to over 2,200, scientistssay. (The volcanoes included are ones whose agesare estimated to be in the range of the Quaternary,but many have not been precisely dated.)

"Monogenetic means 'one life,'" says lead authorGreg Valentine, a University at Buffalovolcanologist. "So a monogenetic volcano will eruptonce, and that eruption may last for several days toseveral decades, but after that, the volcano isbasically dead.

S P Crater, a monogenetic volcano near the city ofFlagstaff in Arizona. Credit: Greg Valentine

"In the United States, most volcanic hazards-related attention has rightly gone to places likeHawaii, and to the Pacific Northwest and Alaska,where we have big stratovolcanoes like MountRainier and Mount St. Helens, which will havemany eruptive episodes over a long life, withwidespread hazardous effects. In the past, thesesmaller monogenetic volcanoes really haven't been

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looked at from a focus on hazards; they have beeninstead studied mainly for what they tell us aboutthe deep earth. Recently, however, there has beenmore buzz in the research community about howwe need to take a look at the kinds of hazardsthese volcanoes might pose.

"My experience with the general public is that mostpeople are surprised to know that there are somany young volcanoes in the Southwest."

The paper's authors are Valentine, Ph.D., professorof geology in the UB College of Arts and Sciences;Michael H. Ort, Ph.D., professor emeritus ofgeology at Northern Arizona University; andJoaquín A. Cortés, Ph.D., senior lecturer of geologyat Edge Hill University in England.

These volcanoes won't erupt again. So whystudy them?

The 2,000-plus volcanoes noted in the paper aredone erupting, so they no longer pose a threat. Butstudying them is important because of the potentialfor new ones to bloom.

"Monogenetic volcanoes tend to occur in areas thatwe call volcanic fields, and the American Southwestis just dotted with these," says Valentine, who grewup in New Mexico. "These are areas of highvolcanic activity where future eruptions couldhappen, but we don't know when, and we don'tknow exactly where."

The peaks of monogenetic volcanoes, viewed acrossLunar Lake in Nevada. Credit: Greg Valentine

The city of Flagstaff, Arizona, is located in avolcanic field where multiple monogeneticvolcanoes have erupted in the past, so a betterunderstanding of possible hazards is important forpeople who live there.

"Two of the most recent eruptions in the Southwestoccurred near Flagstaff about 1,000 years ago, onejust outside of town and the other on the north rimof the Grand Canyon," Ort says. Northern ArizonaUniversity is in Flagstaff. "People living there at thetime adapted to the effects of the eruptions,changing agricultural and cultural practices as wellas where they lived. We will need to do the samewhen the next one erupts. Albuquerque also hasyoung volcanoes along its western margin."

Mercifully, most volcanoes in the southwestern U.S.are in remote locations, away from large populationcenters. In isolated areas, threats from eruptionscould include ash plumes that disrupt travel(including air) or power distribution infrastructure,researchers say.

"One of the younger eruptions in the Southwestoccurred south of Grants, New Mexico a fewthousand years ago, and flowed for many milesparallel to what is now Interstate 40 and part of theBurlington Northern Santa Fe railroad," Ort says. "Asimilar eruption today would take out one of themost important east-west transportation routes inthe country. Several volcanic fields lie along theseroutes, from the Mojave Desert of California toeastern New Mexico, including the one aroundFlagstaff."

"The fundamental pieces of information that youneed to have in order to start understanding thehazards and the chances of a future eruption arethe number of volcanoes, their ages and the typesof eruptions they have," Valentine says. "What weset out to do in the study is find every bit ofinformation that we could about these monogeneticvolcanoes in the southwestern U.S. and compile it

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all in one place. How many of these are there?What are their characteristics? We got informationfrom state geological surveys, published papersand other sources."

A view of Marcath volcano, a monogenetic volcano inNevada. Credit: Greg Valentine

What are the chances of a new eruption within acentury?

Based solely on the total count of volcanoes thathave erupted in the study region during theQuaternary Period, the chances of a new volcanoemerging in the area within 100 years would beabout 8%, Valentine says.

But he notes that this figure embodies lots ofuncertainty. It doesn't account for buried volcanoes,or the fact that a single eruption can create multiplevents. More research will be needed to refine thisestimate and to forecast likely locations for a neweruption.

"There's so much uncertainty here, and this is partof the problem," he says. "It's kind of a wide-openresearch field. When you look at the region fromthe perspective of volcanic hazards, we really havevery little information. Most of the volcanoes havenot been dated, so we don't know how old they are,except that they likely formed sometime within the

Quaternary Period. Very few have been studied indetail."

That said, the study's findings indicate that thefrequency of eruptions across the study region mayapproach that of individual volcanoes in the PacificNorthwest, Valentine and Ort say. The new paperhighlights gaps in knowledge, and the scientistshope that it can act as a launchpad for future, moredetailed research. As Ort and Valentine point out, anew Southwest volcano could appear anywhere inany active volcanic field.

"We don't have infinite resources, so we have toprioritize the efforts we put into forecasting andplanning for hazards," Valentine says. "But how doyou set priorities? If you're monitoring volcanicfields in the Southwest, where do you put theinstruments? Being able to better answer questionslike these is what we're moving toward."

More information: Greg A. Valentine et al,Quaternary basaltic volcanic fields of the AmericanSouthwest, Geosphere (2021). DOI:10.1130/GES02405.1

Provided by University at Buffalo

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APA citation: Examining the 1,800-plus 'young' volcanoes in the US Southwest (2021, November 3)retrieved 1 March 2022 from https://phys.org/news/2021-11-plus-young-volcanoes-southwest.html

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