Volcanic unrest leads to new opportunities for research and collaboration in Argentina

A view of Villarrica from the City of Pucon ten miles away as seen in November, 2025. Photo credit, Jeff Johnson.

-Story by Professor Jeff Johnson

Boise State University Infrasound Lab Manager Jerry Mock traveled to Pucon, Chile, in November 2025 for an international volcano-themed workshop. The trip was a chance to show off new technologies developed in the Boise State lab. What Mock did not know at the outset of his presentation (on Thanksgiving-day) was that two days later he would be traveling across Argentine Patagonia to deploy his instruments at the foot of a remote and restless Andean volcano.

Presenting in front of the international group of volcano seismologists, (earthquake specialists) Mock showed off his instrument, the size of a paperback book, which had been built at Boise State. This was the "Aspen," a compact seismo-acoustic logger that was capable of recording both seismic (ground) shaking as well as sub-audible airwaves radiated by volcanoes. This particular package had been engineered by Research Professor Jacob Anderson of the Department of Geosciences where he is co-director of the infrasound lab. The group's objective is to proliferate infrasound instrumentation, software and science to groups that monitor violent Earth phenomena, including volcanoes, earthquakes, landslides and waterfalls. The prototype on display had recently been completed by Owen Walsh, a masters student in geophysics, who began his involvement as a Boise State undergraduate student working in the lab.

The gathered audience, from 16 different countries, listened attentively to Mock's presentation. After he detailed the technical specifications of the instrument, he gave a live demonstration asking for the audience to stomp their feet (to simulate an earthquake) and to open and shut the auditorium's door (to produce sub-audible, low-frequency soundwaves). In response to these stimuli, waveforms marched across the screen in real time showing well-calibrated, high-fidelity output.

Jerry Mock presenting hardware developed at Boise State University

Mock also showed the audience field data collected only a few days earlier. The conference had been purposefully convened at a foot of a volcano called Villarrica, which often hosts a lava lake boiling benignly at the summit, but which sometimes becomes active enough to threaten local communities (most recently in 2015). Taking advantage of Volcán Villarrica's current calm, he and Professor Jeff Johnson climbed the volcano to install sensors at the summit and record signals from the edge of the crater. They then returned to collect the instruments (and their data) 48 hours later in order to show off a record of activity to the gathered assembly. Mock shared the potentially reassuring news that Villarrica was especially "quiet," much more so than on a previous climb he had made to the top in 2020, and when Johnson lived in Chile during 2015.

Mock's talk was engaging and the capabilities of the portable equipment, easy to carry and easy to deploy, were compelling for the assembled audience. Some audience members showed interest in eventually using such a device in their own research.

The presentation caught the attention of Chilean volcano monitoring professionals who were also present at the conference. Carlos Cardona and Luis Franco, from the Volcano Observatory of the Southern Andes, remarked how useful the integrated seismo-infrasonic sensor would be as a rapid-response tool for awakening volcanoes in Chile. This was a much-needed technology, they said, for a nation with about 100 active volcanoes, half of which are monitored, and many with only minimal infrastructure. The importance of Chile's volcano monitoring need not be debated - it has experienced about a dozen different volcanoes erupting during the last two decades, and two of these erupted practically without warning due to sparse monitoring networks at the time.

During a break in the meeting, Cardona shared information about a potentially awakening volcano some 300 miles north of the conference and situated on the Chilean/Argentine border. Planchón-Peteroa, he said, has a history of activity, with its most recent period of activity commencing in 2018 and with a large ash-rich explosion. Although the volcano's situation is exceptionally remote, and there is minimal local population at acute risk (from pyroclastic flows or lahars), the prevailing winds can drop ash on cities far to the east. It is well known that Planchón-Peteroa could potentially disrupt air traffic from as far away as Buenos Aires, 600 miles to the east.

The Planchón-Peteroa taken from the SEGEMER webcam in Argentina, showing an ash-rich plume.

An Argentine seismologist participating in the conversation was also curious about Planchon-Peteroa's unrest. "We could install sensors in Argentina", he said to Mock. "That is, if you are able to maybe lend us some sensors." Ivan Melchor, of the Universidad Nacional de Río Negro, suggested that a rapid install would be possible from the Argentinian side of the Andes with his enthusiastic logistical support. Given that the Southern Hemisphere was just coming out of its Austral winter, and that the high-altitude passes between Argentina and Chile were still closed, the only reasonable access to Planchón-Peteroa would be a roundabout roadtrip from the east.

Mock, along with Johnson, who was co-organizer of the Pucon workshop, quickly decided this was an opportunity too fortuitous to ignore. They brought a dozen sensors to Chile that were the predecessor to the Aspen. These instruments were called Gems and they were compact, easy-to-deploy infrasound sensors that would be useful to record any volcanic awakenings and/or ongoing activity. They quickly decided it would be feasible to deploy five of those sensors and have them maintained by their new Argentine colleagues to track ongoing activity.

After the conference concluded Friday afternoon, Mock scrambled to retrofit the Gems sensors so that they would accept power from automobile batteries that Melchor would donate to the project from his institution (the National University of Rio Negro). This required that Mock immediately purchase cable, a soldering iron, and dismantle the sensor's power module in order to solder up a new cable. As a lab technician at Boise State this was easy, albeit time consuming work. Meanwhile Melchor called ahead to his university in Argentina to have his car batteries charged and ready to go.

On the next day the team bussed across the Andes to Melchor's home city of Neuquén. The border crossing took them from forested Chile, with its iconic monkey-tree forest, through Argentine and Chilean immigration posts, and in to the arid pampas of Argentine Patagonia. Twelve hours of travel later, in Neuquén, they packed up a 4WD with 50 gallons of reserve diesel, camping gear, 72 hours of food, and - naturally - an immense supply of mate large enough for a team of five, Mock, Melchor, Johnson, and two others from Neuquén, Marcia and Hans. Marcia was a scientist and happened to be Argentina's premiere infrasound specialist, while Hans was driver and master logistics coordinator.

Argentines are united in their love for mate, a tea made from yerba mate leaves, which are steeped in a communal gourd, and sipped from a specialized straw known as a bombilla. During the 12-hour drive to the base of Planchón-Peteroa, the scenery evolved, but the mate was a static fixture. The route from Neuquén to the volcano soon became remote and graveled, eventually paralleling the Andean cordillera north before finally angling northwest toward the Paso Vergara at 9,000 feet above sea level. This border was still seasonally closed, but the road was recently passable. Hans's 4WD Toyota Hi-Lux carried the team through an arid landscape where stunning, exposed geology showed sedimentary deposits interwoven with millennia of volcanic eruptions. The geology was an open book here, with no trees and sparse grasslands found only in spring-fed valley bottoms.

Four miles shy of the international border the team stopped to camp at their deployment site, the Argentine border post and the only building for miles. Situated at the edge of a verdant meadow, with summer cattle grazing and wild horses roaming, it was a bucolic setting and in direct view of the Planchón-Peteroa volcanic system. The camp was six kilometers straight-line path from the active craters and safely outside a four-kilometer radius hazard and exclusion zone recommended by Chilean monitoring authorities. Due to the early November activity the Chileans had put the volcano on watch and issued a yellow alert, the second level of a four-tiered system. That level of warning meant that the volcano was currently restless, but eruptions like the ones that occurred in 2018, and previously in 2010 and 2011 were possible. Hence the need for geophysical monitoring incorporating infrasound.

Planchón-Peteroa, viewed from below, appeared as a complicated volcano and without a classical single pyramidal morphology. Its active craters are situated midway between two 13,000 foot high peaks named Planchón and Peteroa, whose edifices have gradual slopes on opposing sides and ragged vertical cliffs facing inwards. These inward-pointed cliffs ensconce a wide terrace 2,000 feet below the summits pockmarked by multiple small craters, each of which is hundreds of meters in diameter. From that saddle, where the active craters are located, a plume of gas issued upward. Over hours the emissions waned and waxed, occasional feeding a dark-colored gas column, attesting to the volcano's continued unrest.

In the foreground seasonal snow dappled the eastern slopes in the form of large sinuous snow fields. But southwest of the active vents the snow was dirty and gray, contaminated from ash most recently ejected a month earlier. The darkened ash-stained snow contrasted with brilliant white snowfields on nearby high peaks that were upwind of the volcano.

Despite the ever-present wind, the border post would be an ideal, secure place for installation of an array of sensors. The group set up camp in the lee of the border post building and then wasted no time installing sensors within a rocky corral perfect for protection from curious large mammals. The team took time to situate the sensors and geolocate them for positional accuracy. The five sensors were deployed in a configuration known as an array and each microphone was separated by about 30 to 50 feet from its neighbor. Array processing would allow the data to be analyzed and linked to the volcano (as a source) or potentially other sources.

To test the installation the team remained at the site for three nights. During one of the acquisition days there was enough time to scramble up to the summit of Planchón with, hopefully, a birds-eye perspective looking down toward the crater terrace area. Although the summit was reached, it was a much longer climb than anticipated and clouds had moved in obscuring the view down into the crater terrace.

View of Planchón Volcano from the international border and trailhead

Returning to the gendarmerie (Argentine border post) the climbing group was met by a friendly crew of four, on site to help prepare the border post for the coming season. Although the border would not be opened for another ten days they welcomed the science team and extended an invitation for a traditional barbecue inside their structure and away from the Andean wind. Argentina is famed for its cattle and the beef was excellent. The hospitality of the new friends was incredible and the group spent many hours talking about eruptions all over the world and specifically about the restless volcano not far away. Many rounds of mate were imbibed.

The trip back to Chile was another full day of travel, but with sensors left behind at the foot of a restless volcano there was a feeling of accomplishment. Those sensors would provide a continuous record of what Planchón-Peteroa was doing in the coming weeks and months and would in theory provide an uninterrupted chronology of activity, even when the volcano itself was hidden from view by clouds or night. The plan moving forward is for Argentine collaborator Ivan Melchor to retrieve the instruments and their valuable data in three months. In the meantime the team hopes the volcano remains at a low level of activity, but should it ramp up to more violent activity the data will tell a story.

Postscript: Since departing Argentina the volcano has already belched out several clouds of vapor and ash. Incandescence was reported in the crater using satellite observations on Dec. 6, 10 and 12 and ash emissions were most recently reported on Dec. 13 and 14. See the Global Volcanism Program website for more general information about Planchón-Peteroa and other volcanoes worldwide. And visit the Boise State Infrasound Lab for more information about sensors installed.

Acknowledgments: Mock had traveled to Pucon Chile with Professor Jeff Johnson, the infrasound lab's co-direct (along with Jacob Anderson) to present at the IAVCEI volcano seismo-acoustics commission annual workshop. Johnson has worked in Pucon on Villarrica Volcano since 2003, including during its 2015 crisis, and first traveled there with Mock in 2020. Both returned to Pucon to present research and also to make new measurements. Participation in the Chile conference was partially supported by a grant from Boise State University's School of the Arts, which facilitated funding for Mock, Johnson and Professor Ted Apel (Games, Interactive Media and Mobile Technology) presentations of volcano infrasound work.

Share This

• Share on Facebook
• Share on X
• Share on LinkedIn
• Share through Email