BAKU, Azerbaijan: A ‘mud volcano’ put on a fiery display over the Caspian Sea last weekend, as a large explosion and fireball could be seen from Baku, Azerbaijan.

The blast occurred on one of Azerbaijan’s tiny islands, known as Dashli Island.

“There are about 1,100 mud volcanoes that have been identified around the world, and nearly 400 of them can be found in and around Azerbaijan,” said Tyler Roys, AccuWeather Senior Meteorologist, as quoted by United Press International.

“Eruptions of mud volcanoes are driven by a deep mud reservoir that is connected to the surface,” Roys noted.

Like other volcanos, mud volcanos throw boulders and rocks skyward, as well as oil or natural gases.

“The majority, about 86%, of the gas released from an explosion is methane,” Roys said. This highly combustible methane can cause explosions and fireballs that are visible for miles.

Roys noted that popular mud baths maintain lower temperatures, but are part of the same process as mud volcanos.

Additionally, Dr. Mark Tingay of the University of Adelaide in Australia said the Dashli Island mud volcano also experienced “major eruptions” in 1920 and 1945.