An aerial survey by the Philippine Institute of Volcanology and Seismology (PHIVOLCS) on 10 January confirmed the presence of a lava dome inside the summit crater. The lava dome appeared to have a spiny, blocky surface, was emitting voluminous steam, and exhibited slight incandescence. The SO2 emission rate was 2,300 metric tons per day (t/d), high above the 500 t/d level usually observed during quiescent periods. Seismicity related to dome growth remained significant. Deformation measured by electronic tiltmeters on the N flank indicated intrusion of magma into the upper levels of the volcano. Similar activity continued through the 15th. Alert Level 2 (sustained unrest with indications of magmatic activity) remained in effect.

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)