Massive uplift observed in Andean Mountains due to enlarging magma chamber

Sunday, October 14, 2012
By Paul Martin
October 14, 2012

BOLIVIA – Geophysicists at University of California, San Diego (UCSD) have identified a unique phenomenon in Altiplano-Puna plateau, located in the central Andes near the borders of Bolivia, Chile and Argentina. Magma underneath the Earth’s crust is forcing the ground up in one spot, and at the same time sinking the ground around it. The result is something the researchers have described as the “sombrero uplift,” after the popular Mexican hat. According to their report on the phenomenon, published in the journal Science, the two UC San Diego scientists recorded uplift in the crust that measured about 0.4 inches per year for 20 years across an area 62 miles wide; the surrounding area sunk at a lower rate—about eight-hundredths of an inch. “It’s a subtle motion, pushing up little by little every day, but it’s this persistence that makes this uplift unusual. Most other magmatic systems that we know about show episodes of inflation and deflation,” said Yuri Fialko, a professor of geophysics at UCSD and Planetary Physics at the Scripps Institute of Oceanography. Fialko and co-author Jill Pearse said the phenomenon was the result of a diapir, or a blob of magma, that rises to Earth’s crust like heated wax inside a lava lamp. Using satellite data from European Remote Sensing (ERS) and Envisat missions, the geophysicists were able to study the uplift in great detail. In 2006, the team asked for the satellites to gather more data from their orbits over Altiplano-Puna. “It was really important to have good data from different lines of sight, as this allowed us to estimate contributions from vertical and horizontal motion of Earth’s surface, and place crucial constraints on depth and mechanism of the inflation source,” Fialko said. “Back in 2006, it looked like the satellites stopped acquiring data from the ascending orbits over the area of interest. Fortunately, ESA was very responsive to our requests, and generated an excellent dataset that made our study possible. Satellite data and computer models allowed us to make the important link between what’s observed at the surface and what’s happening with the magma body at depth,” he added. Fialko said the study’s findings could fuel future research around magmatic events, including the formation of large calderas. Although this diapir in the Altiplano-Puna plateau appears unlikely to cause such a phenomenon—the creation of large calderas, “supervolcanoes,” are highly destructive events that spew thousands of cubic kilometers of magma into the atmosphere. An event of this type would dwarf the Icelandic volcano eruption in 2011 that ejected large amounts of ash into the atmosphere and disrupted global air travel, Fialko said. Diapirs have been known to exist before, but this new study is the first to recognize an active diapir currently rising through the crust. Fialko said a less prominent uplift phenomenon is taking place near Socorro, New Mexico. The Altiplano-Puna plateau is a highly active area for magma and is part of a South American volcanic arc that extends along the northwest side of the continent. Experts have described the area as the largest known active magma body in Earth’s continental crust. –Red Orbit

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