Rockfalls, small avalanches, moderate steam emission, and fair-to-bright crater glow dominated the visible volcanic activity at Mayon during the week. Partial lava-dome collapses occurred on 11 June at 1347 and on 12 June at 1819. The 11 June collapse produced a small pyroclastic flow that descended the Bonga Gully, reaching an elevation of 1,480 m and producing a thin ash cloud that drifted to the E. The 12 June collapse sparked a period of vigorous, continuous emission of lava fragments for ~1 hour. During the week up to 198 rockfall events were detected per day. A maximum of 2,700 metric tons of SO2 was measured per day, which was lower than the previous week but above the baseline value of 500 tons/day. Alert Level 3 remained in effect, prohibiting entry within the 6-km-radius permanent danger zone. PHIVOLC warned that residents around the volcano, especially those staying in areas facing the Bonga Gully and the SE sector, should be vigilant and prepared to evacuate at any time.

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.

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS), The Philippine Star