Phivolcs: Brace for more Mayon eruptions; danger zone now 9km


LEGAZPI CITY – The phreatic and volcanic eruptions of Mt. Mayon on Monday and Tuesday were just the start and more explosions could be expected from the volcano, Dr. Eduardo Laguerta, the resident government volcanologist in Bicol said here today.

As this developed, Governor Al Francis Bichara said Albay Public Safety and Emergency Management Office (APSEMO)  chief Cedric Daep has extended Mayon’s danger zone to 9 kilometers from 8km on Monday due to the volcano’s activities in the past 24-hour observation period.

Classes as well as work in both government and private sectors were suspended in the municipalities of Camalig and Guinobatan and city of Ligao due to heavy ash fall brought about by the latest eruption at 1:16 p.m. Tuesday, except those engaged in peace and order, health, social services and disaster management.

Also, those employees residing in the affected barangays but are working outside of their municipalities or cities will be excused from reporting, Bichara added.

Laguerta of the Philippine Institute of Volcanology and Seismology (Phivolcs), during a Mayon Volcano media briefing at the APSEMO operations room Tuesday morning said, however, that the possibility of raising Alert Level 5 will depend on the “sustained” hazardous explosive eruption.

It’s not about the frequency of eruptions but the duration, he said.

Laguerta said the pyroclastic materials from the volcano are superheated at at least 1,000 degrees Celsius while the flow’s speed is 100 kilometers per hour, which, he claimed, will increase due to the steepness of Mayon.

On Monday, a dense, five-kilometer tall eruption column was generated by a short-lived phreatomagmatic eruption of Mayon Volcano that lasted eight (8) minutes based on the seismic record.

The event generated pyroclastic density currents or PDCs on gullies and barrancos heading the Miisi, Bonga, Buyuan, Basud, San Andres, Buang, Anoling and other minor rivers within four (4) kilometers of the summit vent, well within the Permanent Danger Zone (PDZ), Laguerta said.

Volcanic ash was blown west and fell on the municipalities of Guinobatan, Camalig, Oas, Polangui and Iriga City.

This was followed by a minor degassing event at 5:51 p.m. that generated a short, 500 meter-high ash plume.

Five (5) episodes of intense but sporadic lava fountaining from the summit crater lasting three (3) to thirty (30) minutes occurred.

The lava fountains reached 500 meters to 700 meters high and generated ash plumes that reached 2.5 kilometers to 3 kilometers above the crater.

The events fed lava flows on the Miisi and Bonga Gullies, sprayed near-vent lava spatter and fed incandescent rockfall on the summit area during the past 24-hour observation period.

A total of two explosion-type earthquakes corresponding to the vertical column eruptions, 15 tremor events, some corresponding to lava fountaining episodes, 35 rockfall events and two pyroclastic density currents or PDCs from lava collapse were recorded by Mayon’s seismic monitoring network.

Rockfall events were generated by the collapsing lava front and margins of the advancing lava flow on the Miisi Gully and by shedding from the summit dome onto the Bonga Gully.

Currently, the Miisi and Buyuan lava flows have advanced to three kilometers and 200 meters, respectively, from the summit crater. Sulfur dioxide gas emission was measured at an average of 992 tons/day on Monday prior to the phreatomagmatic event.

In the afternoon of the same day, Phivolcs raised Alert Level 4 over Mayon Volcano.

As of this writing, there are now 9,906 families affected by the ongoing unrest of Mayon Volcano in Albay which is equivalent to 39,250 individuals.

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