MANILA, Philippines?Strong earthquakes recently rocked southern Philippines near a huge undersea volcano lying north of the island group of Sulawesi and newly discovered by a US-Indonesian ocean exploration team.
The Sulawesi Islands are less than 500 kilometers from Sarangani province.
?This is a huge undersea volcano, taller than all but three or four mountains in Indonesia, and rising more than 10,000 feet (3,300 meters) from the sea floor in water more than 18,000 feet (6,000 meters) deep,? Jim Holden, US chief scientist for the first leg of the expedition, said in a press release.
The volcano is named Kawio Barat, referring to the ocean west of Kawio Islands, and rises around 3,800 meters from the sea floor. In contrast, Mount Apo, the Philippines? highest peak, is 2,954 meters tall.
On July 24, three major undersea earthquakes?roughly within an hour of each other?shook the Moro Gulf off Mindanao, with magnitudes of 6.8 and 7.1 on the Richter scale.
Because the quakes occurred at great depths, their impact dissipated and did not cause any damage on land, according to the Philippine Institute of Volcanology and Seismology.
The institute also said the quakes were tectonic in origin and had nothing to do with the undersea volcano.
Ninety percent of volcanoes erupt in a ?relatively quiet way, similar in manner to the effusion of lava from Mayon Volcano?s crater earlier this year,? according to Mahar Lagmay, associate professor at the University of the Philippines National Institute of Geological Sciences.
If Kawio Barat is one of these, an eruption would only cause lava flow, which would not result in considerable damage to surrounding areas.
?However, if the volcano is like Mount Pinatubo which erupts explosively, it might cause destructive tsunamis,? Lagmay said in a recent interview.
Lagmay recalled the eruption of Krakatoa volcano between Java and Sumatra in 1883, which caused a tsunami that devastated coastal towns and killed about 60,000 people.
?If such a strong eruption would happen now, the damage can be far greater as coastal communities have increased,? he said.
A tsunami and a magnitude 7.8 earthquake, caused by the movement of the Cotabato Trench, struck Mindanao in 1976 and killed some 8,000 people.
The trench is in the vicinity of Kawio Barat.
Ring of fire
A strong eruption might also generate pyroclastic flows with temperatures of about 400 degrees Celsius and speeds of 100 kilometers per hour, Lagmay said.
But if the volcano?s crater is far from the sea surface, water pressure could suppress eruption columns, he added.
The Philippines is part of the ?Pacific Ring of Fire,? which stretches from Indonesia to the coast of Chile in a 40,000-km arc of seismic violence that unleashes earthquakes almost every day and triggers volcanic eruptions.
More than half of the world?s active volcanoes make up the Ring of Fire, which is located at the borders of the Pacific Plate and other major tectonic plates.
The exploration that discovered Kawio Barat is the first joint US-Indonesia ocean expedition. It runs from June to August this year.
Kawio Barat was discovered through the multibeam mapping system of the US National Oceanic and Atmospheric Administration?s Okeanos Explorer ship. The ship?s remotely operated vehicle was able to capture high-definition images of the volcano.
Most of the participating scientists work in exploration command centers in Jakarta and Seattle. They are connected to the ship live via satellite and high-speed Internet pathways, and can interact with shipboard personnel to guide the expedition.
The expedition found shrimps, limpets and a dense population of barnacles feeding on bacteria that grow near volcanic vents.
So far, Okeanos Explorer has mapped more than 6,000 square kilometers of the Indonesian sea floor. With a report from Kristine L. Alave