GWADAR, PAKISTAN – A small island of mud and rock created by the huge earthquake that struck southwest Pakistan on Tuesday has fascinated locals, but experts say it is unlikely to last long.
The 7.7-magnitude quake struck Baluchistan province’s remote Awaran district, killing hundreds of people and affecting hundreds of thousands of others.
Off the coast near the port of Gwadar, 400 km from the epicenter, local residents were astonished to see the dark gray mass of rock and mud that had emerged from the depths of the Arabian Sea.
“It is not a small thing, but a huge thing that has emerged from under the water,” Gwadar resident Muhammad Rustam said. “It looked very, very strange to me — and also a bit scary, because suddenly a huge thing has emerged from the water.”
Enterprising boat owners were doing a brisk trade ferrying curious sightseers to the island, dubbed “Earthquake Mountain” by locals.
Mohammad Danish, a marine biologist from Pakistan’s National Institute of Oceanography, said experts had visited the island and detected methane gas emanating from it. “Our team found bubbles rising from the surface of the island, which caught fire when a match was lit, and we forbade our team to start any flame. It is methane gas,” he said on GEO television news.
The island is about 20 meters high, 90 wide and up to 40 long, he said. It lies around 200 meters off the coast.
The surface is a solid but muddy mix of stones, sand and water with visible cracks, said a man who visited the island. Dead fish and sea plants lay on the surface.
Gary Gibson, a seismologist with Australia’s University of Melbourne, said the new island is likely to be a “mud volcano” created by methane gas forcing material upward during the quake’s shaking.
“It’s happened before in that area, but it’s certainly an unusual event — very rare,” Gibson said, adding that it was “very curious” to see such activity some 400 km from the quake’s epicenter.
The mass is not a fixed structure but a body of mud that will be broken down by wave activity and dispersed over time, he said.
A similar event happened in the same area in 1945 when an 8.1-magnitude earthquake at Makran triggered the formation of mud volcanoes off Gwadar.
Professor Shamim Ahmed Shaikh, chairman of the department of geology at Karachi University, said it happens along the Makran coast because of the complex relationship between tectonic plates in the area. Pakistan sits close to the junction of the Indian, Arabian and Eurasian plates.
“About a year back, an island of almost similar size surfaced at a similar distance from the coast in the Makran region,” Shaikh said.
Gibson said the temporary island is very different from the permanent uplift seen during major subduction zone earthquakes, in which the edge of a plate that has been dragged down by a sinking plate suddenly springs upward. The 2011 Great East Japan Earthquake, for example, elevated the seabed off the Miyagi coast by 3 meters.
In Chile’s massive magnitude 9.5 earthquake in 1960 — the world’s largest on record — whole fishing villages were thrust several meters upward and wharves were suddenly hundreds of meters inland. Such uplift events are relatively common in the Pacific’s Ring of Fire where tectonic plates meet.
An 8.0-magnitude quake that struck the Solomon Islands in 2007 thrust Ranogga Island upward by 3 meters, exposing reefs and expanding the shoreline outward by several meters.
During the 9.2-magnitude temblor off Sumatra that triggered the Indian Ocean tsunami in 2004, several islands were pushed upward while others subsided into the sea. The coast of Aceh in Sumatra dropped by 1 meter and Simeulue Island was lifted by as much as 1.5 meters, exposing the surrounding reef that became the isle’s new fringe.