Report on Mayon (Philippines) — 28 July-3 August 2021
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 28 July-3 August 2021
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2021. Report on Mayon (Philippines) (Sennert, S, ed.). Weekly Volcanic Activity Report, 28 July-3 August 2021. Smithsonian Institution and US Geological Survey.
13.257°N, 123.685°E; summit elev. 2462 m
All times are local (unless otherwise noted)
On 30 July PHIVOLCS lowered the Alert Level for Mayon to 0 (on a 0-5 scale) noting that activity had declined to baseline levels over the previous several months. Ground deformation data indicated tectonic origins rather than magmatic or hydrothermal causes. The frequency of volcanic earthquakes had declined to baseline levels (0-5 events/day) during the previous six months and sulfur dioxide flux had dropped to 156 tonnes/day on 14 July, below the baseline of 500 tonnes/day. Dim crater incandescence from hot gas emissions at the summit continued to be visible in camera images; the last time it was visually observed was in May 2021. 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.