PHIVOLCS reported that during 30-31 May diffuse, short-lived, bluish, hydrogen sulfide emissions rose from Mayon, and incandescence from the crater was observed. Sulfur dioxide emissions fluctuated between 5 and 388 tonnes per day, remaining below the normal level of 500 tonnes per day. Seismicity was low, while a recently concluded ground deformation survey indicated slight inflation compared to February survey data. Based on the visual observations, and despite that most monitoring parameters remained within baseline levels, PHIVOLCS raised the Alert Level to 1 and reminded the public not to enter the 6-km-radius Permanent Danger Zone (PDZ).

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)