Philippines: Mayon volcano update 23 Mar 2000

Report
from European Volcanological Society
Published on 23 Mar 2000
The telemetered seismic network around Mayon Volcano detected nine (9) low frequency and two (2) high frequency volcanic earthquakes and 14 high frequency short duration tremors during the past 24 hours. Ground deformation measurements using Electronic Distance Meter (EDM) at the northwest slope of the volcano showed that the volcano is deflated. The sulfur dioxide (SO2) emission rate increased from 900 tonnes/day (t/d) to 4,400 t/d. During cloud breaks, moderate white steam was observed and drifted towards the northwest.
The volcano is expected to produce a sporadic number of earthquakes and fluctuating volume of Sulfur Dioxide because the volcanic system is still readjusting. However, because no accelerating or increasing trend is indicated by these parameters, PHIVOLCS considers these observation as part of a return to repose conditions. The presence of still-hot magma near the summit causes the crater to glow at night.

PHIVOLCS reiterates to residents living on or near river channels that in case of prolonged and intense rainfall in the volcano area, loose pyroclastic materials deposited along the slopes and river channels are susceptible to erosion and can be remobilized as lahars towards the lower slopes. The areas in which potentially destructive lahars may occur are lowlands fronting the Mabinit and Boyuan-Padang river channels in Legazpi City; Miisi in Daraga; Tumpa, Anoling and Quirangay channels in Camalig; Maninila channel in Guinobatan; Basud-Lidong channel in Sto. Domingo; Bulawan channel in Malilipot; San Vicente and Buang channels in Tabaco and Upper Nasisi and Upper Nabonton in Ligao.

In view of the above, Alert Level 3 remains over Mayon Volcano. This means that there is less probability of hazardous explosive eruption. However, the public is still reminded that sudden small explosions may occur due to localized pockets of gas within the magmatic system. The effects of these explosions are expected to be contained within the 6-km radius Permanent Danger Zone around the volcano and within the 7-km radius Extended Danger Zone in the southeast quadrant. The danger zones should be off-limits at all times. ( from Phivolcs)