Laguna del Maule Volcano: Ground under ancient Chilean volcano is rising fast

Laguna del Maule in the Chilean Andes Mountains. Researchers have found uplift in part of the volcanic field.

Credit: Sarah Strierch / Wikimedia Commons

The Laguna del Maule volcanic field in the Chilean Andes Mountains lies in the heart of volcano country.

The region is a well-known subduction zone, where the friction of one crustal plate sliding under another heats rock to form magma.

But for the last 2,000 years, Laguna del Maule has been a quiet water-filled caldera.

Now, scientists are recording rapid deformation of the land around the caldera, suggesting that a magma reservoir is inflating below the surface.

Helene Le Mével of the University of Wisconsin – Madison, GeoScience dept, presented a poster at the American Geophysical Union’s Fall Meeting in San Francisco Wednesday to share the findings.

Researchers at the Southern Andean Volcano Observatory (OVDAS) monitor and archive volcanic activity throughout the region, but Le Mével said that until now, the observatory had no reason to focus on the Laguna del Maule field. “It’s such an old caldera that there’s nobody there,” she said.

Using a radar technique to measure changes in the level of the ground, Le Mével and her colleagues observed that several areas around and under the lake were rising.

When they set up three GPS stations to confirm this data, the results were startling: The ground is uplifting at a rate of almost 30 centimeters per year, and is now 1.4 meters higher than it was in 2007.

Using this information, the team found that the area is organized as a ring fault – a circular pattern of vents formed as land collapsed inward during the eruptions that created the volcano’s cauldron-like shape.

The area is of particular concern, Le Mével said, because the rock in this region contains a high concentration of silicon dioxide, the tough crystalline material used to make glass.

Unlike magma consisting mostly of basalt, found in the more “flowy” volcanoes of Hawaii, silicic magma very thick. It tends to build up in gluey domes under the surface, and then push upward in a violent explosion.

The scientists estimate that the horizontal reservoir of magma, called a sill, measures 7.5 by 5.5 km, and sits about 5 km underground. Not only is the sill growing, pushing up the earth above it, but its growth is also accelerating.

“At some point, a magma reservoir is always going to erupt when it’s ready, we just don’t know when,” said Le Mével.

She expects to see increasing seismicity right before the eruption, which she said could still be 1,000 years away. But she hopes this new evidence will be enough to fuel further research on the processes driving the deformation.

“We rarely observe large silicic systems that are likely to erupt, even if it’s not next week or next year. And so it’s going to be exciting to follow it. To see how it continues.”

Santorini: The Greek volcano Thera, Behind the Legend of Atlantis, Re-Erupts

One of the largest volcanic eruptions in the past 10,000 years occurred in approximately 1620 BC on the volcanic island of Santorini in the Aegean Sea. 

Following the 1620 BC eruption, much of the previous island of Santorini was destroyed or submerged; this event may have been the inspiration for the legend of the lost continent of Atlantis.

CREDIT: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team

Thera, the volcano that may have given rise to the legend of Atlantis has awakened, researchers say.

The cataclysmic eruptions of Thera on the Greek isle of Santorini about 3,600 years ago that spewed forth about 9.5 to 14.3 cubic miles (40 to 60 cubic kilometers) of lava devastated the ancient seafaring Minoan civilization, potentially inspiring the legend of the lost city of Atlantis.

From the air, the resulting caldera, or volcanic crater, appears as a small cluster within the larger collection of Greek islands in the Aegean Sea.

Over the next four millennia, the largely underwater caldera at Santorini has experienced a series of smaller eruptions, with five such outbursts in the past 600 years, ending most recently in 1950.

After a 60-year lull, Santorini awakened in January 2011 with a swarm of tremors, each magnitude 3.2 or less, new GPS research has revealed.

Magma on the move
Investigators had installed a GPS monitoring system in the area in 2006. These sensors keep track of their location in space, and can thus shed light on when the Earth is moving.

The scientists found that by June 2011, the 22 GPS stations had been pushed 0.2 to 1.3 inches (5 to 32 millimeters) farther from the caldera than they had been just six months earlier.

The researchers then improved the existing GPS stations and installed two more GPS stations, and data from September 2011 to January 2012 showed the land near the volcano was swelling at an accelerating rate, reaching 7 inches (180 mm) of growth per year.

Computer models of the deforming Earth suggested the swelling was due to an influx of nearly 500 million cubic feet (14.1 million cubic meters) of magma into a chamber 2.5 to 3.1 miles (4 to 5 kilometers) below the surface.

The scientists note this ongoing influx of magma does not necessarily signal an impending explosion — this swelling is only a fraction of that behind the Minoan eruption. [10 Wild Volcano Facts]

"We've witnessed similar deformation events at other large calderas — Yellowstone, Long Valley California, and Campi Flegrei — without eruption," said researcher Andrew Newman, a geophysicist at the Georgia Institute of Technology.

"Globally, we've observed that on average, 90 percent of magmatic intrusion events do not reach the surface."

"However, we cannot say for certain that this will not erupt either," Newman toldreporters. "Every volcano is somewhat different, and thus we cannot yet directly relate what we've learned at other volcanoes and apply them with complete confidence to this one." And, even a small eruption can spew dangerous ash, or trigger landslides and tsunamis, the scientists cautioned.

Seismic Image of Yellowstone Hotspot Plume

Seismic imaging was used by University of Utah scientists to construct this picture of the Yellowstone hotspot plume of hot and molten rock that feeds the shallower magma chamber (not shown) beneath Yellowstone National Park, outlined in green at the surface, or top of the illustration.

The Yellowstone caldera, or giant volcanic crater, is outlined in red. State boundaries are shown in black.

The park, caldera and state boundaries also are projected to the bottom of the picture to better illustrate the plume's tilt.

Researchers believe "blobs" of hot rock float off the top of the plume, then rise to recharge the magma chamber located 3.7 miles to 10 miles beneath the surface at Yellowstone.

The illustration also shows a region of warm rock extending southwest from near the top of the plume. It represents the eastern Snake River Plain, where the Yellowstone hotspot triggered numerous cataclysmic caldera eruptions before the plume started feeding Yellowstone 2.05 million years ago.