On 29 March PHIVOLCS lowered the Alert Level for Mayon to 2 (on a 0-5 scale) noting a deflationary trend since 20 February, decreased seismicity, a lower sulfur dioxide flux, and decreased surficial activity. During the previous two weeks the number of rockfalls from collapse of unstable lava-flow deposits fell from a peak of 82 to less than 10 per day. Sulfur dioxide flux ranged from 500 to 2,000 tonnes/day during the previous two weeks, lower than 700-4,500 tonnes/day during 13 January-8 March. Lava last effused from the crater on 18 March, and crater incandescence from hot gas emissions had become faint. Fewer rockfalls and pyroclastic flows were noted as the lava flows stabilized; at 0934 on 27 March one pyroclastic flow traveled down the Bonga-Buyuan drainage and produced a dirty-white ash cloud that drifted SW. During 30 March-3 April a few rockfalls were recorded, there was faint crater incandescence, and steam plumes drifted SW, WNW, and NW. PHIVOLCS reminded residents to stay away from the 6-km-radius Permanent Danger Zone.

Geological Summary. Symmetrical Mayon, which rises above the Albay Gulf NW of Legazpi City, is the most active volcano of the Philippines. The steep upper slopes are capped by a small summit crater. Recorded eruptions since 1616 CE range from Strombolian to basaltic Plinian, with cyclical activity beginning with basaltic eruptions, followed by longer term andesitic lava flows. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic flows and mudflows have commonly swept down many of the approximately 40 ravines that radiate from the summit and have often damaged populated lowland areas. A violent eruption in 1814 killed more than 1,200 people and devastated several towns.

Source: Philippine Institute of Volcanology and Seismology (PHIVOLCS)