Deadly quake in Pakistan creates rare side effect.
A major earthquake hit a remote part of western Pakistan on Tuesday, killing at least 45 people and prompting a new island to rise from the sea just off the country’s southern coast.
The earthquake was so powerful that it caused the seabed to rise and create a small, mountain-like island about 600 meters (yards) off Pakistan’s Gwadar coastline in the Arabian Sea.
Television channels showed images of a stretch of rocky terrain rising above the sea level, with a crowd of bewildered people gathering on the shore to witness the rare phenomenon.
It’s not yet certain what caused the new ground to appear. Speculation is that it was a mud volcano, a fault scarp or the result of a landslide. Scientists will check out the feature in the daylight hours. Older residents recalled that this had happened before, in 1968, as the result of a mud eruption due to seismic movement. The resulting island eroded in a year.
Ground uplift can occur after an earthquake. This is an excellent piece describing sudden geomorphic changes at a subduction zone.
Here are other examples.
I’ll follow this story to see what new information is found. Stay tuned for updates.
UPDATE (26-Sept-2013) More has come to light about the newly emerged land offshore of Pakistan as people land on it and investigate. It is made of sand, some rock, solid rock and mud. The sediment is emitting methane gas. It’s an oval shaped island about 250ft to 300ft (76-91m) in length, and about 60 to 70ft above the water.
Rashid Tabrez, the director-general of the Karachi-based National Institute of Oceanography, says the energy released by the seismic movements of these fault-lines activates inflammable gases in the seabed.
“The seabed near the Makran coast has vast deposits of gas hydrates, or frozen gas having a large methane content,” he explained.
“These deposits lay compressed under a sediment bed that is 300m-800m thick.”
“When the plates along the fault-lines move, they create heat and the expanding gas blasts through the fissures in the earth’s crust, propelling the entire sea floor to the surface.”
The island that popped up near Gwadar is the fourth in this region since 1945, and the third during the last 15 years, he said.
There is a video at the above link which describes how this is a relatively common side effect from quakes near shore. The sea bed will be disrupted at least temporarily. It is not expected that this new island will last very long and may erode away and/or sink within a year.
Tip: Jeb Card