PHIVOLCS characterized activity at Mayon as “decreased unrest” during 12-19 December. The seismic network recorded 1-4 daily volcanic earthquakes and 1-2 rockfall events during 12-15 December. The summit was occasionally obscured by weather conditions, though on most days emissions were visible drifting in multiple directions. The Tokyo VAAC reported that at 1447 on 17 December an ash emission was identified in a satellite image rising to 2.4 km (8,000 ft) a.s.l. and drifting WSW based on satellite data and information from PHIVOLCS. The Alert Level remained at 2 (on a 0-5 scale). Residents were reminded to stay away from the 6-km-radius Permanent Danger Zone (PDZ) and pilots were advised to avoid flying close to the summit.

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 periods of andesitic lava flows. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic density currents 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)