Are mud volcanoes true volcanoes?
A mud volcano is what caused the explosion near an oil field in the Caspian Sea off Azerbaijan this week (July 4, 2021). Thats according to a report by an Azerbaijani press agency. It happened on Dashly Island, also known as Ignatiy Stone Island, a volcanic island. A famous Roman naturalist, Pliny the Elder, described a mud volcano in the year 77 AD. Yet they are still a most poorly understood natural phenomenon. The July 4 mud volcano happened near oil industry installations in the sea. Some speculated at first that the explosion might be centered near an oil rig. In fact, the closest video of the Dashly mud volcano was captured from an oil platform. This is no coincidence. Mud volcanoes and the oil industry go hand-in-hand. These unique geologic features are found near oil deposits and serve as an indicator for where these valuable natural resources lie. Because theyre driven in part by natural gas. Mud volcanoes arent true volcanoes in the same sense as igneous volcanoes. Most volcanoes we hear about are driven by molten rock from below, called magma. Instead, mud volcanoes are driven by hot water and natural gas. They tend to occur where layers of water-saturated clay rocks, in Earths interior, are under pressure from layers above. Pressure from nearby gas can drive this mud upward, from deep within the Earth up toward the surface. The force of the gas can cause rocks and mud to shoot outward in an eruption, along with methane and carbon dioxide. Most mud volcanoes are small, just a few inches to several feet (a meter or so) high. You might have seen such mud volcanoes at Yellowstone National Park, where theyre called mud pots. But some larger mud volcanoes can rise over 300 feet (100 meters) above the surface. Mud volcanoes found in water may never produce enough material to rise above the water level, while others create islands around the volcanic activity. Dashly Island is one of these. And sometimes, a large mud volcano erupts so explosively that it spews gas plumes that spontaneously combust, sending up columns of fire into the sky. Thats what we saw happen this week in the Caspian Sea. This weeks mud volcano in Azerbaijan  Mud volcanoes exist around the world, from Indonesia to Italy and beyond. Even Mars has mud volcanoes. But some of the greatest concentrations of mud volcanoes on Earth exist near Azerbaijan. This country and its coastline along the Caspian are home to nearly 400 mud volcanoes. Thats more than half the total found throughout Earths continents. Both people offshore on oil platforms and those on the boardwalk of the nearby city of Baku, Azerbaijans largest city and capital, captured video of the July 4 volcano. The fiery eruption lit up the night sky. Many shared videos on Twitter, some of which you can see below. WATCH: Large explosion reported near oil platform in the Caspian Sea; officials say it may have been caused by a mud volcano pic.twitter.com/eqwNw110bF  BNO News (@BNONews) July 4, 2021  The morning light allowed a closer look at the source of the explosion: the mud volcano that created Dashly Island. The last recorded eruption on this island was in 1945. Places where natural gas seeps from the Earth are often associated with mud volcanoes. Not far from Dashly Island, onshore near the city of Baku, Azerbaijan, theres a gas seep known as Yanar Dag, or Burning Mountain. Its a place where fire has been burning continuously out of a seam in the Earth. A shepherd accidentally lit the flame in the 1950s, and its been burning ever since. Mud volcanoes, found in the area, are another way for the pent-up natural gases to be released from underground. Mud volcano seen from space  This explosion was detected by the @JPSSProgram #SuomiNPP VIIRS Day/Night Band, which is also sensitive to lights & gas flares on the numerous oil platforms in the #CaspianSea. No obvious lights in the area of the explosion before the July 4 event. #Azerbaijan @CriticalStress_ https://t.co/M3aEHiqqDX pic.twitter.com/c888f7JUzk  Simon Carn (@simoncarn) July 5, 2021  Bottom line: A mud volcano erupted in spectacular fashion in the Caspian Sea off Azerbaijan on July 4, 2021.