Mayon Volcano is now on phreatic eruption, also called a phreatic explosion or ultravulcanian eruption. It occurs when magma heats ground or surface water. The extreme temperature of the magma (anywhere from 500 to 1,170 °C (932 to 2,138 °F)) causes near-instantaneous evaporation to steam, resulting in an explosion of steam, water, ash, rock, and volcanic bombs.
Here’s the post from Gov. Joey Sarte Salceda, Chairman, Albay PDRRMC:
“Phivolcs Director Rene Solidum called me that at about 8am, there was an ash explosion of at least 500m in height but on precautionary warnings since it was essentially steam-driven. There are unconfirmed media reports that a casualty may have been sustained due to mountaineering (mostly conducted without notice/approval) caught surprised by the sudden volcanic behavior.
In view of this, while Mayon is on “Alert 0”, we advise the following:
1. Extra care and caution in conducting human activity in the 6-km PDZ – this includes ATV, trail runs, picnics etc.
2. We reiterate that Mayon Volcano mountaineering (or volcanoeering) is subject to prior notification to PTCAO/APSEMO/DOT”
Mayon Volcano’s last activity is on July 2009 to January 2010. Phreatic explosion like this happened last July 10, 2009 where PHIVOLCS raised the status from Alert Level 1 (low level unrest) to Alert Level 2 (moderate unrest) because the number of recorded low frequency volcanic earthquakes rose to the same level when a phreatic explosion occurred last August 2008. On January 13, 2010, PHIVOLCS reduced the alert level from 3 to 2, saying that this indicated a further reduction in the likelihood of hazardous eruption.