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Mayon update, 20 December 2009: alert level raised to 4 20 December 2009

Posted by admin in activity reports, eruptions, Mayon, Philippines.
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The alert level for Mayon volcano was raised on 20 December by the Philippine Institute of Volcanology and Seismology (Phivolcs) to level 4, ‘hazardous eruption imminent’. Mayon Bulletin no. 7 explains:

This is to notify the public that PHIVOLCS-DOST is now raising the alert status of Mayon Volcano (13.2576 N, 123.6856 E) from ALERT LEVEL 3 to ALERT LEVEL 4. This means that a hazardous explosive eruption is possible within days, thus, areas expected to be affected by such eruption will be accordingly extended.

To ensure the safety of the public, PHIVOLCS-DOST is recommending an extended danger zone from the summit of 8 km at the southern sector and 7 km at northern sector.

Areas just outside of this Extended Danger Zone (EDZ) should prepare for evacuation in the event explosive eruptions intensify.

The previous bulletin, Mayon Bulletin no. 6, issued earlier on 20 December, reported 222 volcanic quakes and tremors over the preceding 24 hours, one of which was an explosive event that produced a 500 metre altitude grey ash column. Harmonic tremor was continually recorded. Steam plumes varied from dirty white to light brown in colour. Intensified crater glow and the continuous rolling down the slopes of incandescent material was visible at night. Lava had advanced 4.5 km downslope from the crater. Sulphur dioxide emissions were measured at 7,024 tonnes/day, a marked increase on the 2,034 tonnes/day reported in Mayon Bulletin no. 5 on 19 December.

The head of the Phivolcs volcano monitoring team has told the press that the alert level was raised on the afternoon of 20 December ‘because there was a sudden acceleration in the activity of the volcano’:

He said the number of volcanic quakes from 6:00 am Sunday (2200 GMT Saturday) increased to 463 and that the volcano was belching more sulphur dioxide into the air.

This was a sign that ‘a hazardous eruption is possible within days.’

However he would not give an estimate of when the eruption could take place.

Meanwhile, weather forecasters report that a storm is threatening the southern Philippines with heavy rains, increasing the lahar risk at Mayon. Destructive and deadly lahars have been a feature of Mayon’s history: most recently, a typhoon in November 2007 turned deposits left by the eruption of July to October 2006 into disastrous mudflows, killing and injuring thousands. It is grim experiences like this that lie behind the urgency of the current evacuation effort around Mayon.

UPDATE: A new report in the Inquirer gives Phivolcs figures of 463 earthquakes registered at Mayon between 08:00 and 14:00 on 20 December.

For all our Mayon coverage: Mayon « The Volcanism Blog.

Philippine volcano alert raised, eruption in days – govtPhilippine Daily Inquirer, 20 December 2009
Eruption within daysManila Bulletin, 20 December 2009
Mayon alert level raised to 4; eruption seen within days – GMANews.TV, 20 December 2009
Major volcanic eruption feared in Philippines – Associated Press, 20 December 2009
Alert level 4 raised as volcano seen to erupt in daysPhilippine Daily Inquirer, 20 December 2009

Global Volcanism Program: Mayon – summary information for Mayon (0703-03=)
Philippine Institute of Volcanology and Seismology – website for Phivolcs

The Volcanism Blog


1. Chance Metz - 21 December 2009

It’s gonna blow! Almsost 2,000 earthquakes in one day!

Mayon Volcano Bulletin 8
21 December 2009

7:00 AM

Mayon Volcano’s (13.2576 N, 123.6856 E) activity escalated during the past 24-hour observation period. Seismic activity dramatically increased in number and size. A total of 1,942 volcanic earthquakes was detected by the seismic network. Many of these volcanic earthquakes were recorded at maximum deflection and continually occurred beginning at 1221H yesterday. Harmonic tremors were also continuously recorded.

Sulfur Dioxide (SO2) emission rate remained very high at 6,089 tonnes per day (t/d). Audible booming and rumbling sounds were first reported in the eastern flank of the volcano at about 1455H then occasionally occurred beginning 2200H last night. Intensified crater glow and rolling down of incandescent lava fragments from the crater was also persistent. Red hot lava also continuously flowed down along the Bonga-Buyuan, Miisi and Lidong gullies. Lava fountains rising approximately 200 meters above the crater were observed at 2007H, 2008H and 2018H. The lava front has now reached about 5 kilometers downslope from the summit along the Bonga-Buyuan gullies.

Alert Level 4 is hoisted over Mayon Volcano, meaning a hazardous eruption is possible within days. Thus, PHIVOLCS-DOST reiterates that the Extended Danger Zone (EDZ) from the summit of 8 km on the southern sector of the volcano and 7 km on the northern sector be strictly observed. Areas just outside of this EDZ should prepare for evacuation in the event hazardous explosive eruptions intensify. Active river channels and those perennially identified as lahar prone in the southern sector should also be avoided especially during bad weather conditions or when there is heavy and prolonged rainfall. PHIVOLCS–DOST is closely monitoring Mayon Volcano’s activity and any new significant development will be immediately posted to all concerned.

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