Mayon threatens big eruption

LEGAZPI CITY, Philippines – Mayon Volcano threatened a big eruption yesterday as magma continued to rise towards its surface.

Ed Laguerta, Philippine Institute of Volcanology (Phivolcs) chief volcanologist in Bicol, said magma intrusion is taking place inside Mayon as its surface remains inflated.

However, the volume of sulfur dioxide emission could not be measured due to rains over the 8,077-foot volcano, he added.

Laguerta said that they will analyze the new images of the lava dome taken during an aerial survey yesterday morning.

The findings will be presented in today’s media briefing at the Albay Public Safety and Emergency Management Office, he added.

Laguerta  told The STAR a small eruption might occur once rainwater seeps into the crater and makes contact with fresh magma at the upper vent of Mayon.

“Once rainwater touches portion of the magma, it might spark a small explosion that in turn may disturb the degassing process and trigger big secondary eruptions,” he said.

Laguerta said heavy rains and clouds around Mayon were preventing scientists from getting the correct volume of sulfur dioxide emission needed to determine whether the degassing process has been sustained due to magma intrusion towards the surface of Mayon.

“For three days now we could not determine the accurate volume of sulfur dioxide emission due to the presence of non-volcano clouds over Mayon,” he said. “Right now, the correct measurement of gas emission is very important in determining the actual condition of this volcano.”  

Laguerta believes the sudden drop in sulfur dioxide emission could be attributed to the bigger lava dome that had blocked more than half of the 250-meter wide mouth of Mayon.

“We are not including volumes of SO2 emissions if we are in doubt that they are contaminated by heavy rains or presence of thick clouds,” he said.

Phivolcs recorded yesterday only one rockfall event in the past 24-hour period, and maintained the 308 tons a day SO2 emission measured three days ago.

Laguerta predicted a hazardous explosion should Mayon continue its surface inflation while the clogged crater is preventing gas from escaping from the crater.

A drop in volcanic earthquakes and rockfall events is not always reliable in determining that Mayon’s overall condition is already going back to normal, he added.

Eduardo Villacorte, Phivolcs science research specialist, said pressure build-up has increased somewhere along the column due to a clogged magma conduit  hindering the ascent of new magma towards the vent and the lava dome at the crater surface.

He could not say until when the magma column would be able to hold the amount of pressure inside.

Villacorte said factors determining the explosive potentials of magma are viscosity, water content and crystals, considering that the magma at Mayon is andesitic.

Sulfur gas emission dropped to 138 tons Saturday, way below the reading last Thursday at 308 tons per day, he added.

Villacorte said a pressure build-up at the magma chamber can also trigger an ash-driven explosion.

Villlacorte said more magma would result in more gas, and if the pressure exceeds the strength of the surrounding rocks inside the magma chamber Mayon would erupt. – With Celso Amo