Mayon Volcano Update [2 January 2010]

Philippines experts out of step with Mayon?

Mayon may be gradually returning to the repose period: Phivolcs

The information coming out of PHIVOLCS and the decisions made by the state volcanologists concerning the volcano’s hazard status are at best inconsistent with the history of Mayon’s eruptive activity.

Highlights from the news, eye-witness accounts, official and unofficial reports on Mayon’s status during  the past 24 hours:

• Phivolcs is lowering Mayon’s alert status from level 4 to level 3 [hazardous explosive eruption less likely]
• Volcanic quakes down to 13 events (majority of events associated with rockfalls, and rolling  of lava fragments down the mountain)
• No tephratic eruptions for the 3rd day
• Sulfur Dioxide emission rate of 2,621 tons per day up (more than twice the amount previous day), but down from a high of about 9,000 tons.
• Small amount of steam emitted

Mayon Volcano Bulletin 20 released by PHIVOLCS on 2 January 2010

The seismic monitoring network around Mayon Volcano (13.2576 N, 123.6856 E) detected 13 volcanic earthquakes and 68 rockfall events related to the detachment of lava fragments at the volcano’s upper slopes during the past observation period. Emission of weak volume of white steam at the summit crater was observed during cloud breaks yesterday. Sulfur Dioxide (SO2) emission rate was measured yesterday morning at an average value of 2,621 tonnes/day.

The latest activity of Mayon still indicates that its overall state of unrest remains relatively high.  However, this phase of unrest, characterized by moderate seismicity, high volcanic gas outputs and continuing glow of the summit are processes normally associated with very gradual return to the repose period.  The volcanic system is expected to continue producing earthquakes and to vent a large amount of gases because fresh magma still resides along the whole length of the volcanic pipe and near the summit.

From 28 December to present, a declining trend in Mayon volcano’s activity was noted as reflected by the following observations:

1.      No ash ejections were observed since 29 December. Steam emission was most of the time weak and white in color indicating considerable decrease in energy and absence of ash.

2.      Majority of the type of earthquakes that were recorded during the past days were associated with rockfalls and rolling down of fragments from the lava deposits along Bonga gully and the advancing lava front.

3.      Measured SO2 levels have also showed a decreasing trend from a maximum of 8,993 tons per day to 2,621 tons per day. The still high concentration of SO2 gas emission suggests that there is residual magma degassing at shallow depth.

In view of the above observations, PHIVOLCS-DOST is lowering the alert status of Mayon from Alert Level 4 to Alert Level 3 to reflect the overall gradual decrease of activity. Alert Level 3 means that there is less probability of a hazardous explosive eruption.  However, the lowering of the alert level from 4 to 3 should not be interpreted that the unrest of the volcano has ceased. If there is resurgence in the volcano’s activity and the potential for explosive eruptions is perceived to be forthcoming, the alert level may be raised back to 4 but if there is noticeable downward trend in the monitored parameters, then the alert will be further lowered to Alert Level 2.

For previous entries, additional information, photos and links to Mayon Volcano see links below:

• Could Blue Moon Trigger Mayon Explosion?

• Mayon Pipes Down, for Now

• Mayon Calmer, But it Could Be the Lull Before the Storm

• The Raging Lava Mill

Related Links:

• Mayon Volcano Links Page [Recent Posts, Photos, Videos and Comments]
  
• FEWW Volcano Links
• Volcanoes
• FEWW Earthquake Links