Mayon’s cone perfect again

LEGAZPI CITY — Mount Mayon’s perfect symmetry, ruined by previous eruptions, has been restored by the continuous flow of lava since July 14, and the volcano will maintain its perfect cone shape if no violent explosions occur, scientists said yesterday.

Ed Laguerta, the volcanologist who has witnessed Mayon’s eruptions over the past four decades, said that if its current "quiet eruption episode" remains merely strombolian — an explosion characterized mainly by lava extrusion — the 2,462-meter Mayon will regain its old glory of being the only volcano in the world with "perfect symmetry."

"Mayon’s scars and cracks that were inflicted on its slopes by the 1984 and the succeeding eruptions are at this stage now completely healed by viscous lava," he said.

Laguerta said the gullies and cracks that marred Mayon’s slopes have been filled in by lava. This is particularly true of the Bonga gully, which before July 14 had an estimated width of 300 meters and depth of 160 meters.

"The crack that created the upper portion of the Bonga gully was a result of the very strong explosion episode during the 1984 Mayon eruption," he told The STAR.

Laguerta, however, explained that if Mayon graduates from mere lava extrusion to strong explosions, tremors and shaking underneath the volcano might again damage the patched-up portions of its slopes.

"We just hope that it will remain strombolian so that it could fully self-heal through lava flow," he said.

Laguerta said Mayon’s perfect cone was the product of past eruptions that were characterized by lava extrusion, which formed part of its every eruption episode.

"The usual pattern of Mayon eruption is phreatic, or ash explosions; followed by vulcanian, or scalding of grayish ash columns and pyroclastic flows; and then culminate to strombolian, or lava extrusion," he explained. "That’s why it now has a perfect symmetry."

However, Laguerta said Mayon’s present activity has deviated from its past eruption patterns, saying its lava flow has lasted for more than 20 days.

"But if it remains strombolian, aside from restoring its beauty, it will also minimize the dislocation of residents residing at its foot," he said.

Mayon continues to draw tourists near its six-kilometer radius permanent danger zone because of its spectacular spewing of lava and other incandescent materials of different sizes that tumble down its slopes.

The Philippine Institute of Volcanology and Seismology (Phivolcs) maintained alert level three over Mayon yesterday despite a drop in the volume of sulfur dioxide emission, saying the continued detection of low frequency volcanic tremors indicated that there was continuing magma ascent towards the surface.

Phivolcs also reminded residents outside the six-kilometer declared danger zone to be on constant alert against pyroclastic flows and to be prepared for massive evacuation any time alert level four is raised. — Cet Dematera