High in the southern Andes, Chile’s Quizapu crater is one of South America’s most fearsome geologic features. In 1846, it was the source of one the continent’s largest historically recorded lava flows. In 1932, it produced one of the largest recorded volcanic blasts. The eruptions instantly turned vast mountain areas to desert. The volcano is currently inactive, but could revive at any time. What is next? For eight days, scientists and students from Columbia University’s Lamont-Doherty Earth Observatory and four other institutions traveled the region on foot and horseback to study what drives such huge eruptions at Quizapu and elsewhere. (All photos by Kevin Krajick) READ THE FULL SCIENTIFIC STORY or WATCH A VIDEO
Led by Lamont-Doherty volcanologist Philipp Ruprecht, the team crosses a giant lava flow—nearly 10 miles wide in places—that Quizapu produced in 1846. The dark rocks are the lava; the travelers are walking on a dusty blanket of pumice that rained down in 1932, burying much of the lava.
During the two-day walk to the Quizapu area, team members navigate peaks and valleys of raw cinders and eroded lavas. The Chilean Andes are built on eons of tectonic uplift and frequent volcanism; active peaks are ranged in the distance.
In this roadless, waterless region, a foot expedition requires help. Hired arrieros—rural livestock herders—bring in strings of pack horses to carry water, food and equipment.
Silvestre “Don Carmelo” Adasme, leader of the arrieros. The volcano destroyed many mountain pastures where his ancestors and neighbors once herded livestock. But his family still keeps horses, cattle, sheep and goats in outlying areas that were spared.
At the top of a high pass, a student takes in his first view of Quizapu’s world. To the left, craters left by prehistoric explosions. To the right, 12,970-foot Descabezado Grande volcano. Almost everywhere, apparent snow; but actually, the whitish stuff is pumice from Quizapu’s last explosion. (The source crater is not visible here.)
Sunset on the valley floor below fires up Descabezado Grande (left) and its companion peak, 12,428-foot Cerro Azul. The Quizapu crater lies hidden on Cerro Azul’s flank.
As night falls in the mountains, temperatures plunge. Students and scientists take advantage of a fire built from scavenged fragments of shrubs.
Francisco García Araya, a graduate student at Chile’s University of Concepción, shovels into an ash deposit. Like an archaeological dig, excavations through successive layers can tell a story of a volcano’s past.
Frequent lava flows and ash falls create dead-end drainages where lakes can form. But even in the presence of water, rock-strewn landscapes remain largely lifeless.
Lamont-Doherty volcanologists Einat Lev (left) and Elise Rumpf launch a camera-equipped drone over the great lava flow. They will assemble hundreds of high-resolution aerial images into a detailed topographical map, aimed at understanding the forces that directed the flow.
Razor-edged lava boulders on a lower arm of the flow.
Team members trudge upward through fine pumice debris, on their way toward the source crater.
The researchers take numerous lava samples for later analysis. University of Chile graduate student Rayen Gho attacks a boulder.
University of Chile graduate student María Angélica Contreras checks a lava sample. Subtle differences in texture and composition provide hints about the eruption’s origins.
In one sample, researchers spot a greenish crystal of olivine—a deep-earth mineral rarely seen at Quizapu that usually is lost on its way up. The intact crystal suggests that some of the magma driving the eruption came from the depths quickly—maybe reaching the surface within days or weeks.
Lamont-Doherty postdoctoral researcher Megan Newcombe examines a lava block that developed distinct flow bands as it oozed along.
At a rare oasis where pasture has managed to re-emerge, warm springs are fed either by still-cooling lava or continuing magmatic activity. University of Michigan geologist Adam Simon takes his only bath of the trip.
Luis Riquelme (left) and Roberto Aránguiz perform the daily morning chore of loading up the horses. The animals were amazingly strong, surefooted and patient.
Due to simple gravity, the pumice fragments expelled from Quizapu get progressively bigger as you near the crater. University of Hawaii PhD. student Emily First (left) and Lamont-Doherty volcanologist Einat Lev are strong, but it also helps that bubble-filled pumice is lighter than your average rock.
High up on Quizapu’s flanks, the pumice bombs are monstrous—a measure of the power behind the volcano.
The final climb to Quizapu’s 10,000-foot-high rim is a heartbreaker: thin air, extreme slopes, loose rubble. One scientist later admitted to crying on the way up.
Shortly after reaching the top, the team traverses Quizapu’s rim. The crater–only a small part is visible here–is about a half-mile wide and 1,000 feet deep.
University of Hawaii geologist Julia Hammer notes the crater’s structure. Its walls show a tortured history of repeated heating, deformation and explosions. Colorful stains indicate the rocks could be rich in valuable metals.
At the edge of the abyss, Ruprecht and Hammer remove a sample of the terminal scoria—the final layer of debris spit out during the volcano’s last gasps.
View from below the crater rim, on the way back to camp. Even in summer, snowfields dot the high elevations.
On the last night in the field, the arrieros expertly prepare a lamb for roasting over an open fire.
Fresh horses arrive and at last the researchers get to ride for a few hours on the way back to civilization.
AGU25, the premier Earth and space science conference, takes place December 15-19, 2025 in New Orleans, Louisiana. This year’s theme—Where Science Connects Us—puts in focus how science depends on connection, from the lab to the field to the ballot box. Once again, Lamont-Doherty Earth Observatory and Columbia Climate School scientists, experts, students, and educators are playing an active role, sharing our research and helping shape the future of our planet. #AGU25 Learn More
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