Philippines

Philippines: Mayon volcano update 07 Mar 2000

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At 0746 H, a parallel collapse of the new lava flow deposit in the upper middle slopes produced a voluminous secondary pyroclastic flow. The billowing ash cloud descended the Bonga Gully to the southeast.
During the rest of the past observation period the volcano has exhibited quiet lava effusion. This was manifested by intense crater glow and rolling incandescent materials along the upper and middle reaches of the Bonga Gully. Moderate to strong emission of steam drifted generally to the northern sectors from the summit crater. The high steam output also yielded an elevated Sulfur Dioxide (SO2) emission rate of at least 8,800 tonnes per day.

Seismic activity consisted of 11 low-frequency volcanic quakes and 25 episodes of short-duration tremors. Slight inflation of the lower northwest flank of the volcano continued to be recorded by ground deformation measurements.

The lava extrusion, high seismicity, high gas emission rate and continued swelling of the edifice suggest that the volcano remains at a state of unrest.

Mayon Volcano's status is being maintained at Alert Level 5. The 6-km Permanent Danger Zone and the extended 8-km danger zone in the southeast quadrant remain in effect. The airspace to the west and southwest of the volcano are now generally clear of airborne ash. However, some hot lahar flows may occur due to the presence now of highly erodable pyroclastic deposits which may be remobilized during heavy rainfall. Potential sites for lahar flows include the Mabinit and Buyuan-Padang river channels in Legaspi City; Miisi and Anuling channels in Daraga; Basud-Lidong channel in Sto. Domingo; Bulawan channel in Malilipot; San Vicente and Buang channels in Tabaco; and upper Nasisi in Ligao. Authorities are advised to monitor the condition of the major roads crossing these channels and in particular those channels radiating southeast of Mayon. PHIVOLCS reminds the people residing near river banks as well as in low-lying areas that these sites are most susceptible to potentially destructive and life-threatening flows. Temporary evacuation of the said areas may be necessary in case of sustained and intense rainfall.