Philippines: Mayon volcano update 29 Mar 2000

At 2355H an audible hissing sound originating from the crater was heard at the northwest lower slope of the volcano. Similar events occurred at 2356H and 0132H today and were recorded as low frequency type volcanic earthquakes. Nine (9) low frequency and seven (7) high frequency volcanic earthquakes and four (4) episodes of high frequency short duration tremors were detected during the past 24 hours. On the other hand, the Sulfur Dioxide (SO2) emission rate dropped from 8,500 tonnes/day (t/d) to 1,200 tonnes/day (t/d). Steam emission from the summit varied from weak to moderate and drifted north-northwest. Crater glow was still observed during the night.
The moderate number of recorded volcanic earthquakes is due to the readjustment the volcano is still undergoing after it erupted. As expected, the residual magma that remains at the whole length of the volcanic pipe and near the summit continue to release large amount of volcanic gases. Crater glow will also be continually observed due to the still hot lava deposit at the summit crater.

PHIVOLCS maintains Alert Level 3 over Mayon, meaning that there is less probability of hazardous explosive eruption. However, the public is reminded that sudden explosion 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-kilometer radius Permanent Danger Zone around the volcano and within the 7-kilometer radius Extended Danger Zone in the southeast quadrant. The danger zones should remain off-limits to everybody including trekkers, tourists and other visitors. It is important to note that independent of alert level, the new lava flow deposits are very unstable and a large proportion of pyroclastic deposits is still susceptible to erosion and subsequent remobilization as secondary pyroclastic flows, lahars or debris flows. Residents living near river channels are, therefore, reminded that should rainfall become intense and prolonged, pyroclastic materials deposited along the slopes are susceptible to erosion and subsequent remobilization as lahars or debris flows towards the lower slopes. The areas in which potentially destructive volcanic lahars may occur are lowlands fronting the Mabinit and Boyuan-Padang river channels in Legaspi City; Miisi in Daraga; Tumpa, Anoling and Quirangay channels in Camalig; Maninila channel in Guinobatan; Basud-Lidong channels in Sto. Domingo; Bulawan channel in Malilipot; San Vicente and Buang channels in Tabaco and Upper Nasisi and Upper Nabontan in Ligao( From PHIVOLCS)