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Tale of two magmas may be to blame for explosive volcanic eruptions

  • Author: Ben Anderson
  • Updated: September 27, 2016
  • Published October 15, 2012

The last time the Las Cañadas volcano erupted was more than 150,000 years ago, but scientists from the University of Southampton in the United Kingdom studying the volcano's explosive past say they have determined what causes massive eruptions like the prehistoric blast.

The Las Cañadas volcano has seen at least seven major eruptions in the last 700,000 years, and according to a new study published in Scientific Reports, they may now have found the root of the devastating blasts. The history of the caldera -- located on the island of Tenerife in the Canary Islands -- is well documented, but the new research is the first to nail down a possible cause of such eruptions.

"Despite considerable scientific interest in the volcano and associated hazards including major landslides, little is known about the triggers for these large-scale events," the study's authors write.

Knowing what caused the eruptions could be key to developing an advance warning system before the volcano erupts again, which would prove devastating to the island populated today by more than 900,000 people.

According to researchers, the eruptions were caused when younger, hotter magma mixed with cooler, older magma within the volcano, causing a buildup of pressure that resulted in ash and debris columns reaching 15 miles into the air.

"By comparison, even the smallest of these eruptions expelled over 25 times more material than the 2010 eruption of Eyjafjallajökull, Iceland," a report from the University of Southampton said. That eruption disrupted European air travel for nearly a week as ash caused hazards to aircraft.

Researchers determined the Las Cañadas trigger by examining igneous rocks formed during the previous eruptions, when "crystal mush" lining the walls of the underground magma chamber mixed with magma left over from the blast. Those rocks indicated the blending of the two types of magma and the resulting explosion.

Another serious eruption from the volcano in the Canary Islands, off the northwest coast of Africa, has the potential for major impacts across that continent and Europe, so knowing what causes the eruptions could be key to an advance warning system.

"Our findings will prove invaluable in future hazard and risk assessment on Tenerife and elsewhere," said Dr. Tom Gernon, one of the authors of the study. "The scale of the eruptions we describe has the potential to cause devastation on the heavily populated island of Tenerife and major economic repercussions for the wider European community."

Whether the same combination of old and new magma could be responsible for similar eruptive events in the last hundreds of thousands of years isn't clear, but the new study represents a good jumping-off point for further research.

You can read the full study here.

Contact Ben Anderson at ben(at)

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