Ballooning Magma Creates Sombrero-Shaped Formation

ENVISAT satellite collecting data of the spot of magma uplift over South America. CREDIT: Image created by Yuri Fialko, SIO/UCSD, using imagery and artwork from ESA and NASA View full size image

A giant, sombrero-shaped rock formation is growing in the Andes as magma bobs up like a blob in a lava lamp, new research has found.

These findings, detailed in the Oct. 12 issue of the journal Science, could shed light on the birth of supervolcanoes capable of eruptions far greater than ever seen in recorded history, the scientists that investigated the phenomenon said.

The team of researchers looked at the largest active body of magma in Earth's continental crust, a zone about 180 miles (300 kilometers) wide and 3,300 feet (1,000 meters) thick and lying at a depth of about 11 miles (18 km) under the Altiplano-Puna plateau in the central Andes region. This area at the border of Argentina, Bolivia and Chile has experienced intense volcanism for about 10 million years.

Shaped like a sombrero

After analyzing 20 years of satellite and seismic data of the region's surface with computer models, the researchers suggest the magma is ballooning, forming a vast buoyant sphere in the middle of the crust that is bobbing upward. This blob is technically known as a "diapir," and this research is the first to identify an active magma diapir rising through the crust in the present day.

The diapir has caused the surface above it to rise at a nearly constant rate of about 10 millimeters (0.4 inches) per year for at least two decades. That is about the rate at which fingernails grow.

A still from an animation illustrating "sombrero uplift," with a central peak surrounded by subsidence. CREDIT: Yuri Fialko, SIO/UCSD
CREDIT: Yuri Fialko, SIO/UCSD

View full size image

"It's a subtle motion, pushing up little by little every day, but it's this persistence that makes this uplift unusual," said researcher Yuri Fialko, a geophysicist at the Scripps Institution of Oceanography at the University of California, San Diego. "Most other magmatic systems that we know about show episodes of inflation and deflation." [50 Amazing Volcano Facts]

In the broader picture, Earth's surface is getting pushed up across an area about 60 miles (100 km) wide while the ring surrounding it sinks. This has led to a geological oddity the shape of a wide-brimmed Mexican sombrero hat.

Supervolcano clues?

This "sombrero uplift" could help yield insights on the initial stages of the births of supervolcanoes, which are capable of eruptions dwarfing anything ever recorded by humanity, spewing out thousands of times more magma and ash than even the catastrophic Krakatoa eruption of 1883.

"Those were truly disaster-type events," Fialko said. "We know they did happen in the Altiplano-Puna area in the past."

The researchers noted that sombrero uplift might also be taking place elsewhere on the planet.

"Activity observed around Socorro, N.M., provides a very interesting comparison to that observed in the Altiplano-Puna," Fialko told OurAmazingPlanet. "The Socorro anomaly is centered on the second- largest active magma body known on continental crust."

The Socorro anomaly shares a number of remarkable similarities with the Altiplano-Puna, such as a large volume of molten rock at similar depths, seismic activity in the upper crust, and a long-term uplift of the surface.

"In fact, in the case of Socorro we have evidence that the uplift persisted for at least 100 years," Fialko said. "Such similarities may be suggestive of a common mechanism."

This story was provided by OurAmazingPlanet, a sister site to LiveScience. Follow OurAmazingPlanet on Twitter @OAPlanet. We're also on Facebook and Google+.