A huge explosion has been seen off the coast of Azerbaijan in the Caspian Sea on Sunday, sending plumes of black smoke and flames into the sky but none of the many oil farms in the area were damaged and no-one was hurt. The explosion sent a column of fire into the sky. A large fireball was visible across the region, officials and witnesses say.The fire continued to smoulder into Monday. Footage circulating on social media showed the huge blaze visible from the coast. The fire had been caused by a mud volcano, which spews both mud and flammable gases. “The mud volcanoes in Azerbaijan are some of the biggest and most violent in the world. There are, on average, several large mud volcano eruptions each year, and many of them can have big fires,” Dr Mark Tingay, a geophysicist at the University of Adelaide, explained on Twitter
. Mud volcanoes are caused by water being heated deep within the Earth that mixes with rocks and minerals when they erupt. About 400 of the world’s estimated 1,000 mud volcanoes are in Azerbaijan. There are known to be dozens of these just off the Azerbaijani coast line, and in the past several have ignited local deposits of gas and oil to form spectacular explosions and fires. This activity is what gives the country its nickname of “Land of Fire”.