CAUGHT IN THE
'RING OF FIRE' RP IS A DISASTER-PRONE
COUNTRY
[PHOTO
AT LEFT - Mayon volcano in Albay, one of the country’s most active volcanoes,
emits smoke in a recent photo. The Philippine Institute of Volcanology and
Seismology is keeping Mayon’s alert level at No. 1 and maintaining a permanent
six-kilometer- radius danger zone. Photo By VAL RODRIGUEZ]
MANILA, June 18, 2006 (STAR) By Sheila Crisostomo - Sitting on the western edge of the "Ring of Fire" in the Pacific Ocean, the Philippines is a disaster-prone country.
It contains some 300 volcanoes, 22 of which are active based on history of recent eruptions.
And every day, the country is shaken by at least 20 earthquakes. Fortunately, few are strong enough to be felt.
The Ring of Fire refers to a band of volcanoes and fault lines that circles the basin of the Pacific Ocean.
Also known as the circum-Pacific seismic belt, it is shaped like a horseshoe and is 40,000 kilometers long.
The fault line stretches from Chile, northwards along the South American coast through Central America, Mexico, the west coast of the United States and the southern part of Alaska, through the Aleutian Islands to Japan.
It stretches downward to the Philippines and Indonesia before curving back toward New Guinea, the southwest Pacific islands and New Zealand.
Almost 90 percent of the world’s 1,500 or so active volcanoes are within the Ring of Fire, with 81 percent of them considered as the most dangerous.
The explosion of Mt. Pinatubo on June 9, 1991 was one of the three largest eruptions within the Ring of Fire in the 20th century. This happened after 500 years of dormancy.
At present, the Philippine Institute of Volcanology and Seismology (Phivolcs) is monitoring the country’s eight most active volcanoes.
These are Pinatubo at the tri-boundary of Zambales, Pampanga and Tarlac; Mayon in Albay, Taal in Batangas, Kanlaon in Negros Oriental, Hibok-Hibok on Camiguin island and Bulusan in Sorsogon.
According to Phivolcs director Renato Solidum, only Mayon, Taal, Kanlaon and Bulusan are presently "exhibiting volcanic activities."
But even with four volcanoes recording activity at once, this does not support an "end-of-the-world scenario," he said.
Solidum noted it is a normal occurrence for even four volcanoes to become restive from time to time.
He pointed out that volcanoes have separate magma chambers which are not connected, no matter how close they are to each other.
"Mayon and Taal are both on alert level one. They are not erupting but they have parameters which are abnormal," he added.
Solidum explained that Mayon sometimes gives rise to volcanic earthquakes.
At night, the crater of the volcano could be seen glowing, indicating that lava or molten rocks are almost near the surface.
Known for its almost perfect cone, Mayon has a record of 47 eruptions since 1616. But the most destructive of these was in Feb. 1, 1814 when the town of Cagsawa was buried in lahar, killing around 1,200 people.
Only the bell tower of the town church remained as the mute witness of the eruption.
On the other hand, Taal has been exhibiting "above normal" volcanic tremors, Solidum said.
The volcano has erupted violently several times, prompting the International Association of Volcanology and Chemistry of the Earth’s Interior to designate it as a "Decade Volcano," making it the focus of research and mitigation plans.
Taal sits inside a body of water known as Taal lake which is found inside a caldera approximately 25 by 30 kilometers wide. It last spewed ashes a few months ago.
Phivolcs records showed there were several theories as to how the Taal caldera was formed but the most popular is that it resulted from the destruction of a larger Taal cone after several eruptions or one major catastrophic event.
After the catastrophic collapse, a smaller cone, the Taal volcano island, probably developed within it.
Bulusan volcano, on the other hand, last awakened on March 31. It has since registered seven phreatic or steam-driven ash explosions.
Solidum added there were indications that the magma inside Bulusan was rising to the surface but its full extent has yet to be known.
The level of sulfur dioxide flux of the volcanic plume in Bulusan appeared unstable while its slopes were swelling.
Phivolcs said the recent volcanic activities in Bulusan indicate that an eruption is imminent.
However, Solidum said Bulusan would never erupt like Pinatubo since they have different types of rock deposits.
Bulusan has a summit elevation of 1,565 meters and is located some 70 kilometers southeast of Mayon.
The first recorded eruption of the volcano was in 1852.
Phivolcs released a bulletin yesterday reporting that Bulusan showed "low to moderate levels of unrest with fair probability of more explosions." No ash emission was monitored, however.
Kanlaon, on the other hand, started becoming active last June 13, emitting ashes and steam. Standing at 2,435 meters, the volcano has erupted 23 times since 1866 up to 2005.
Phivolcs observed, however, that Kanlaon was "generally quiet" from 8 a.m. last Friday to 8 a.m. yesterday, with only one high-frequency volcanic earthquake picked up by seismic monitoring network.
Solidum noted Kanlaon’s reactivation might have been caused by groundwater and rainwater coming in contact with hot rock very close to the surface of the volcano.
"And the sudden conversion of water into steam will trigger ash emission… The activity in Kanlaon is shallow," he added.