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Mayon: alert level raised, evacuation plans aired 12 July 2009

Posted by admin in activity reports, Mayon, Philippines.
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Unrest is continuing at Mayon volcano on the Philippine island of Luzon. The Philippine Institute of Volcanology and Seismology, Phivolcs, raised the alert level on 10 July from Alert Level 1 (low level unrest) to Alert Level 2 (moderate unrest). The Phivolcs bulletin explains:

Beginning June 2009 monitored parameters indicated an increase in the current activity of Mayon Volcano. The number of recorded low frequency volcanic earthquakes rose to a higher level signifying possible movement of magma beneath the volcano edifice at shallow depth. The present seismic count is at the same level when a phreatic explosion occurred last August 2008. Ground uplift of about one centimeter was measured by Precise Leveling Survey conducted last June 15-22, 2009 and the uplift was sustained during a re-survey yesterday, July 9, 2009. Glow at the summit crater has intensified and could now be observed at Lignon Hill Observatory without the aid of telescopes. Steam emission was at moderate level.

Aerial survey conducted last July 08, 2009, showed a cone-shaped pile of hot, steaming old rocks, possibly remnants from previous eruptions which could be the source of the glow at the crater. The low frequency volcanic earthquakes and ground uplift could indicate that fresh volcanic materials are moving upward at depth, causing the formation of the cone-shaped pile of materials at the crater.

The 6 km radius Permanent Danger Zone (PDZ) around the volcano and a 7 km Extended Danger Zone (EDZ) on the south-eastern flank have both been declared off-limits by Phivolcs because of the danger of explosions and lahars. According to a report in the Philippine Star, Mayon’s current behaviour is leading Phivolcs to warn of a potentially hazardous explosive eruption:

Ed Laguerta, resident volcanologist for Bicol of the Philippine Institute of Volcanology and Seismology (Phivolcs), said unlike the 2006 eruption that was characterized by slow-paced lava flow, the present condition of Mayon could lead to a hazardous eruption and it would be dominated by pyroclastic flow, a very hot gaseous volcano material ranging from 300- to 1000- degrees celcius in temperature and travels faster than lava.

According to one news report, some 500 people living in small villages within the 6 km danger zone are to be evacuated this weekend, while another report says that residents of the town of Guinobatan are already leaving their homes in fear of an eruption. Yesterday the same station was reporting that the Governor of Albay Province (where Mayon is located) had said that nearly 7000 people would need to be evacuated if the volcano’s unrest escalates and Phivolcs raises the Alert Level to 3:

In the latest situational report on Mayon’s activity issued on Saturday by the National Disaster Coordinating Council (NDCC), [Albay Governor] Salceda said that 1,675 families or 6,996 persons will be evacuated from villages near the volcano once the Philippine Institute of Volcanology and Seismology (Phivolcs) hoists Alert Level 3 in the area.

Plans are being put in place for a possible evacuation, including the identification of schools to be used as evacuation centres and the dissemination of information among the local population. Philippine President Arroyo has stepped in and ‘reminded Secretaries Gilberto Teodoro Jr. (Defense) and Esperanza Cabral (Social Welfare) of the government’s “zero casualty” policy’.

Meanwhile, some locals are reluctant to evacuate – a phenomenon all too familiar from certain other areas of volcanic risk.

Mayon now under alert level 2, Phivolcs says – GMANews.TV, 10 July 2009
500 residents around Mayon face evacuation – Inquirer.net, 10 July 2009
7,000 to be evacuated if Mayon activity heightens – GMANews.TV, 11 July 2009
7,000 around Mayon ready for evacuation – Inquirer.net, 11 July 2009
PHIVOLCS watches Mayon closelyPhilippine Star, 12 July 2009
Arroyo moves to ensure welfare of Mayon folk – GMANews.TV, 12 July 2009
Hard-headed farmers at Mayon’s danger zone won’t be evacuatedBusiness Mirror, 12 July 2009

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

The Volcanism Blog



1. damon hynes - 12 July 2009

What’s the difference in the precursors between 2006 and 2009? I remember news accounts in ’06 that said a climactic eruption was ‘days away’…and as time passed and the lava kept flowing, a lot of people were puzzled, myself included. So what is the ‘present condition’?

2. Boris Behncke - 13 July 2009

Dear Damon,

the problem with many volcanoes is that they can erupt in different ways, and that predicting the exact character of their activity (as well as its timing) is about as difficult as saying when you will have your next flu, how long it will last, and how serious it will be. You can only rely on the signs the volcano gives you, and sometimes these seem to indicate something much bigger than actually happens. There are cases when a volcano seems about to blow full force and then, in the last moment, it decides not to do so. What should be clear is that each time that a volcano which has produced powerful and destructive eruptions in the past shows signs of reawakening, this should be taken very serious. If the outcome were less dramatic than expected, this should be taken positively.
In any case, there are two kinds of challenge which have to be faced in present-day volcanology (and related civil defense) – one is volcanoes that are a bit undecided, like Rabaul (Papua New Guinea), which seemed ready to erupt already in 1984 but erupted only ten years later), or others that decide very fast, like Kasatochi (Aleutians) in 2008. The other challenge is the people living in the areas at risk, and with them their authorities, civil defense, and the news media. They want to hear simple and precise statements about the volcano is going to do, and as shown above, this is not always very easy to do. There are often locals who believe to know the volcano much better than anybody else and that it will do them no harm (Harry Truman at Mount St. Helens in 1980 being the most famous example). And truly enough, unnecessary evacuation may be a cause of tremendous economic loss and thorough distress for the concerned population. So, although volcanology has made amazing progress in recent decades, a few uncertain variables remain and will probably do so for a long time.
Hopefully the imminent Mayon eruption (if it happens now) will be a great show rather than anything threatening.

3. damon hynes - 21 July 2009

Hi, Boris–sorry about taking so long to reply–life getting in the way!

I agree with your observations about human nature and the news media. I hit the Filipino television and newspaper sites whenever something is happening in the Archipelago volcanically, and they are certainly sensational (like Fox and CNN in the U. S.!)

This might be an outdated measurement, but years ago one thing to watch out for was the ratio of SO2 to CO2, and I was wondering if this or some similar measure was causing Philvolcs to pronounce an explosive eruption. Because if the same measurements were observed in 2006 and the effusive eruption resulted, what was different now?

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