What Is a Mud Volcano? Huge Explosion Rocks Oil-Rich Caspian Sea

An explosion rocked the Caspian Sea on Sunday, with an Azerbaijan oil company stating the cause was due to a "natural burning mud volcano."

The blast is reported to have taken place around six miles from the Umid gas field, Ibrahim Ahmadov, a spokesman for the SOCAR state oil company, told Azerbaijani news agency APA, and around 46 miles off the coast of Azerbaijani capital Baku.

In a statement published on Facebook, SOCAR confirmed none of its industrial facilities were damaged in the fire and they continue to operate as normal.

It added, translated from Azerbaijani: "In this case, SOCAR's staff were sent to the scene to determine the cause of the fire seen in the sea. Between Alat settlement and Neftchala city, a natural burning mud volcano was observed on the island of Dashli, approximately 30km from the shore."

The flame has since been extinguished, the company said in a tweet. It added: "It should be noted that the eruption of mud volcanoes due to their connection with oil and gas fields has led to the release of methane and other flammable gases in the past."

However, the company did not explain how the gases could have been ignited in the first place—though it is possible for this to happen naturally. It is also unclear whether any wildlife has been affected.

Newsweek has contacted SOCAR for comment.

In 2020, the journal Nature stated that over 1,000 mud volcanoes had been identified around the world, both on land and underwater. It said the Caspian Sea has the densest distribution of mud volcanoes anywhere in the world.

Britannica states some mud volcanoes form when underground hydrocarbon gases mixed with mud force their way upward to the surface, spewing mud into a conelike shape. Others may form when gas and water chemically react with surrounding rocks to form a boiling mud.

Videos of the Sunday fire posted to Twitter show a bright ball of flame erupting from the site, which extends high into the air before reducing in size slightly.

Mark Tingay, a petroleum geologist at the University of Adelaide in Australia who has researched mud volcanoes, launched a Twitter thread discussing the fireball.

He said it is possible that mud volcanoes can erupt naturally, though scientists are not entirely sure how.

Tingay said one possible reason is that rocks can produce sparks as they are banged together in the eruptions; others say the rapid pressure change alone could ignite the gas.

He said the mud volcano on Dashli Island had major eruptions in 1920 and 1945.