South America's "Black Giant" Volcano Is Showing Early Warning Signs Of Potential Collapse

An eruption of Ecuador's Tungurahua volcano in 1999 forced the evacuation of 25,000 people from neighboring communities. Ecuadorpostales/Shutterstock

 

One of South America’s most active volcanoes is showing early warning signs of “potential collapse” that could result in a far-reaching landslide, new research suggests.

Scientists are studying the potential for a flank failure at Tungurahua volcano, one of the most destructive processes on Earth, whereby a portion of a volcano collapses and creates landslides and explosive eruptions. Recent activity of the 5-kilometers-high (3 miles) volcano paired with a weakening western flank may make the volcano more likely to collapse, creating landslides with the potential to cause widespread damage to the area.

In the indigenous tongue of the Quechua peoples, Tungurhua means 'Throat of Fire'. Known locally as "The Black Giant,” the stratovolcano in the Eastern Cordillera of the Ecuadorian Andes has been “persistently active” since 1999 when activity forced the evacuation of 25,000 people from nearby communities. In November 2015, the volcano experienced multiple explosions and heightened seismic activity that displaced about 3.5 centimeters of sediment in around three weeks. But 3,000 years prior, the west flank of the volcanic cone partially collapsed, creating a widespread debris avalanche or rock, soil, snow and water over 80 square kilometers (30 square miles), leaving in its wake a massive scar.

Scientists have taken recent activity and compared it with ancient geophysical and geochemical monitoring of the volcano to test different physical mechanisms that might lead to a flank collapse.

“Using satellite data we have observed very rapid deformation of Tungurahua's west flank, which our research suggests is caused by imbalances between magma being supplied and magma being erupted,” said study author James Hickey of the Camborne School of Mines in a statement.

Map of Tungurahua volcano. The dashed blue line indicates the scar of the flank collapse 3,000 years ago and the blue diamond is the summit vent. Colored, transparent shapes indicate the footprints of deformation episodes. Earth and Planetary Science Letters

Modeling systems combined with visual observations of surface deformation show that a magma storage region below the volcano is likely creating a zone of “preferential weakness.” Stress along this region had collapsed previously, which can be magnified by the buildup of magma over time. If it continues, the volume can create enough stress that would add to more instability so that if a volcanic eruption were to occur, it may impact this already weakened region, resulting in a large collapse of the flank.

“Magma supply is one of a number of factors that can cause or contribute to volcanic flank instability, so while there is a risk of possible flank collapse, the uncertainty of these natural systems also means it could remain stable. However, it's definitely one to keep an eye on in the future,” said Hickey.

Researchers say that the history of the volcano and its magma-related stress must be considered alongside other triggering factors. In particular, magma transport and storage have implications for volcanic hazards, especially those with histories of flank collapsing. They advise closely monitoring the volcano for stronger signs of potential collapse.

“Shallow magma transport and storage are key dynamic processes at the heart of hazard assessment and event forecasting for eruptive activity and flank collapse. The results of this study highlight the importance of monitoring volcanoes with a history of flank collapse and how this can be incorporated into routine geophysical and geodetic volcanic surveillance,” write the authors in Earth & Planetary Science Letters.

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