I M Ready Asks: What kinds of volcanic eruption should we worry about?

As Mayon continues to show signs of an impending eruption, the question is: how powerful would its 2014 eruption be? 

 

Despite over 40 recorded eruptions over the centuries, Mayon has had relatively mild eruptions. These include small volcanic ash fall eruptions and lava flows trickling down its many valleys. 

A few times, however, stronger eruptions occurred such as the 1814 eruption that buried the famous Cagsawa Church and the more recent 1968 eruption. In both cases, pyroclastic flow eruptions were recorded—the most dangerous kind of eruption. 

 

Pyroclastic Flows (PFs) are a mixture of ash, hot gases and fluids that rolls down the flanks of a volcano. These can travel with speeds above 700 km/hr and reach temperatures exceeding 500 degrees centigrade. The French call it "nuee ardente", literally translating to glowing cloud because of the rolling ash cloud's incandescent nature. Curiously enough, much of what we know about PFs started when volcanologists were at hand to observe small PFs on the south side of Mayon when it erupted in 1984.

 

In August 2006, 30,000 people living near Mayon were evacuated for fear of a pyroclastic flow eruption which occurred at a smaller scale than expected. However, four months after the eruption, Super Typhoon Reming passed by Bicol. The rain from Reming mixed with the freshly-deposited volcanic ash in Mayon and brought down the volcano in the form of lahars. We know lahar and its long term and widespread impact very well as these have affected Central Luzon for many years after Pinatubo's eruption in 1991.

 

Following high volcanic activity in the past few days, the region of Albay is currently under alert level 3. The evacuation of 2,898 families from the 6 to 8 km permanent danger zone around Mayon has been completed, and government officials are urging tourists to stay out of the danger zone.

 

According to Ed Laguerta, resident volcanologist of the Philippine Institute of Volcanology and Seismology (PHIVOLCS), Mayon is showing activity similar to that of 2001, specifically both lava and pyroclastic flow.



The lava flow of volcanoes in the Philippines is too slow to pose a threat to people, only 3 km per day, affecting only agricultural lands. PHIVOLCS has yet to receive any report of people dying due to lava flow.

 

Laguerta said, however, that a hazardous eruption from Mayon in the coming weeks is possible. — With a report from Bea Montenegro/TJD, GMA News

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Dr. Carlos Primo "CP" David is a geology professor at the University of the Philippines-National Institute of Geological Sciences (NIGS). He earned his Ph.D. in Environmental Science and Geology from Stanford University and is the project leader of DOST's Climate X. Dr. David is also the Head of GMA's IM Ready Group.