US Geological Survey

A magnitude 7.7 earthquake that struck Pakistan today has likely killed hundreds of people, and perhaps many more. It also may have triggered the eruption of a mud volcano hundreds of kilometres away off Pakistan’s coast, generating media reports of a new island that had not existed before.

Pakistan lies in a geologically vulnerable spot between two tectonic collisions. Toward the west, the Arabian plate of Earth’s crust dives beneath Eurasia. Toward the east, the Indian plate does the same. Most of the movement is accommodated by north-south movement along Pakistan’s Chaman Fault, which may be responsible for today’s quake.

The epicentre lies 270 kilometres north of the city of Karachi in a relatively remote and mountainous region. Given the poor to nonexistent building codes, many buildings have apparently collapsed. The US Geological Survey estimates that 44,000 people were exposed to severe shaking and thousands may have perished. In 2005, a magnitude-7.6 earthquake in Kashmir killed at least 86,000 people.

The new island was reported in the Arabian Sea, about 600 metres off the Gwadar coastline and hundreds of kilometres from the epicentre. This region is known for its mud volcanoes, which form when mud or fluid is squeezed out of underlying sediment and spreads a brown mush over everything. The description of the island, and its distance from the quake’s epicentre, is consistent with a mud volcano, says Michael Manga, a geoscientist at the University of California, Berkeley, who coauthored a 2009 review paper on the subject.

In 2001, a magnitude-7.7 earthquake in Pakistan initiated a mud eruption 482 kilometres away, Manga says. And mud volcano islands have appeared along this part of the coast before. Typical mud volcanoes measure tens of metres high, he adds — enough to break through the water’s surface and form new land.

The world’s most famous mud volcano, Indonesia’s Lusi, has been burbling muck since 2006.