Jakarta Globe, Nurdin Hasan, April 15, 2010
Banda Aceh. Local residents claim the seabed near Banyak Island in Aceh Singkil district, Aceh, has risen dramatically since the 7.2-magnitude earthquake on April 7.
They also say they have seen an undersea fissure spewing out mud and rocks. But experts are not so sure about the supposed geological phenomenon.
Banyak islander Mufliadi told the Jakarta Globe the phenomenon was first noted on Tuesday by fisherman Ruslan, who had been trawling for sea cucumbers in the Gosong Turak waters around Pailana Island, just off Banyak.
“He was shocked and came back to tell us what he’d seen because the site is a prime fishing spot for the local fisherman,” Mufliadi said on Thursday.
Ruslan had been shocked to find layer upon layer of rocks and no fish in the area. The fisherman also reported a 10-meter-long fissure shaped like a frying pan.
Before the quake, the water in Gosong Turak had been 20 to 30 meters deep but now was just five meters, he said.
On Wednesday, hundreds of villagers dove into the water to see the change for themselves and take rock samples.
“The black rocks were the size of a person’s head, and crumbled easily,” Mufliadi said. “When we burned the rocks, a very strong odor was emitted.”
He said the villagers were concerned the fissure could be an undersea volcano because it kept spewing mud.
Mufliadi urged local authorities to survey the area to confirm what was happening and ease villagers’ concerns.
“If the fissure really is a volcano, we want to anticipate and be ready for the worst-case scenario,” he said.
Mufliadi said more people visited the area on Thursday, bringing back yellow stones “that looked like gold.”
Banyak Island subdistrict head Safnil confirmed the seabed was silting, after visiting the area. “There is a geological anomaly underwater, shaped a bit like a volcano, that keeps spewing out mud,” he said. “But the mud isn’t hot like lava from a regular volcano.”
Safnil said many Banyak residents were worried. He urged them to remain calm and alert pending the arrival of geologists to study whether the fissure posed a threat.
But Danny Hilman Natawidjaya, a geologist from the Indonesian Institute for Sciences (LIPI), told the Jakarta Globe it was impossible for the seabed to have risen so much. “The maximum the seabed can rise is one meter,” he said. “If it did really happen, there should have been a major landslide near the area.”
Danny also said the anomaly that looked like a volcano was called liquefaction. “It’s normal, as the layer of sand on the seabed is pushed by the quake until it liquefies and forms a volcano and can spew out mud,” he said.
Danny said earthquakes altered the land and sea structure and sometimes fish left to find a more comfortable habitat.
Additional reporting by Nurfika Osman
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