PHIVOLCS reported that a "cone-shaped pile of hot, steaming old rocks," possibly from a previous eruption of Mayon, were seen during an overflight on 8 July and may be the source of recent summit incandescence. On 9 July, a leveling survey revealed that 1 cm of uplift previously measured during 15-22 June had been sustained. Incandescence at the summit crater had also intensified and was visible from the Lignon Hill Observatory (about 11 km SSE) without the aid of telescopes. Steam emissions were also noted. On 10 July, PHIVOLCS raised the Alert Level for Mayon from 1 (low level unrest) to 2 (moderate unrest) on a scale of 0-5.

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)