Deadly mudflows threaten residents near erupting Mayon volcano

Millions of tons of ash and rocks from an erupting Mayon volcano could bury nearby communities due to heavy rain, authorities said Saturday, as tens of thousands flee over fears of a deadly explosion.

The official Philippine Institute of Volcanology and Seismology (PHIVOLCS) issued the warning as heavy rains lashed the surroundings of the Mayon volcano, which has been emitting flaming lava and giant clouds of superheated ash for about a week.

Rainwater could combine with the volcanic ash and rock to form deadly, fast-moving mudflows — called "lahars" — that could sweep away entire settlements, authorities said.

"If there is ash fall and heavy rain, it can be converted into (a) lahar," PHIVOLCS chief Renato Solidum told AFP.

"The important thing is to move out in case of heavy rains... this is a precautionary measure."

A report on 24 Oras Weekend said some parts of Legazpi City have become flooded due to continuous heavy rain over the region on Saturday.

Some residents were having a hard time crossing streets due to the brown-colored floodwaters, which Solidum described as "muddy stream flow" and not lahar.

Solidum, however, said that muddy stream flow still poses danger to residents.

In its advisory issued 10:30 a.m., PHIVOLCS said thick pyroclastic density current deposits could generate lahars either by themselves or by incorporating existing erodible material on channel banks.

PHIVOLCS warned that streamflows could be generated along all river channels, especially the Buyuan, Miisi, Mabinit, Basud, San Vicente, Buang, Quirangay and Masarawag-Maninila  river channels.

Communities and local government units beside these river systems were advised to be more vigilant and to move residents to high ground when heavy rains occur.

Seismologists said PDC deposited so far in watershed areas was measured at 9 million cubic meters, mostly in the Buyuan and Miisi channel watersheds, excluding unverified deposits on the northern flank.

Meanwhile, the total volume of ashfall on the western sector is roughly 1.5 million cubic meters.

The institute earlier said in an advisory that 25 million cubic meters (about 883 million cubic feet) of ash and other volcanic material had recently been emitted by Mayon, settling on its slopes and the surrounding area.

It warned that this could result in lahars flowing into waterways and called on officials to move residents near rivers to higher ground.

An explosion of the 2,460-meter (8,070-foot) Mayon in August 2006 did not directly kill anyone but four months later, a typhoon unleashed an avalanche of volcanic mud from Mayon's slopes that claimed 1,000 lives.

Phivolcs said Mayon had emitted fountains of lava on Friday but bad weather was preventing observation of the volcano's activity on Saturday.

Volcanic mudflows have been a perennial problem during and after volcanic eruptions in the Philippines, which sits on the "Ring of Fire" — islands in the Pacific that were formed by volcanic activity.

Alert Level 4 remains in effect over Mayon Volcano, which means a hazardous eruption could still be possible within hours or days.

The government has already evacuated more than 84,000 people from a "danger zone" stretching as far as nine kilometers (six miles) around Mayon over fears of a possible deadly eruption.

Mayon, located about 330 kilometers (205 miles) southeast of the capital Manila, is the most active of the country's 22 volcanoes — and one of the deadliest.

Four foreign tourists and their local tour guide were killed when it last erupted in May 2013.

In 1814, more than 1,200 people were killed when lava flows buried the nearby town of Cagsawa. — with Margaret Claire Layug and Saleema Refran/MDM/ALG, Agence France-Presse