An island emerged from the Caspian Sea after a mud volcano erupted in early 2023. By the end of the following year, it had nearly eroded away, retreating from view like an apparition. Powerful eruptions of the Kumani Bank mud volcano have produced similar transient islands several times since its first recorded eruption in 1861. Also known as Chigil-Deniz, the feature is located about 25 kilometers (15 miles) off the eastern coast of Azerbaijan.
The OLI (Operational Land Imager) and OLI-2 on the Landsat 8 and 9 satellites captured these images showing the island emerge and shrink. In November 2022 (left), the crest of the volcano remained below the sea surface. By February 14, 2023 (middle), an island had appeared, and a sediment plume drifted away from it. Additional satellite observations suggest the island emerged between January 30 and February 4 and measured approximately 400 meters (1,300 feet) across, said University of Adelaide geologist Mark Tingay. By the end of 2024 (right), a greatly diminished portion of Kumani Bank was visible above the water.
Kumani Bank’s previous eight recorded eruptions occurred in bursts lasting less than two days and produced islands of different sizes and longevities. A May 1861 event resulted in an island just 87 meters (285 feet) across and 3.5 meters (11.5 feet) above the water. This one eroded away by early 1862. The strongest eruption, in 1950, produced an island 700 meters (2,300 feet) across and 6 meters (20 feet) high.
Mud volcanoes are “weird and wonderful features that remain largely understudied and little understood,” said Tingay in a seminar for the Geological Society of Australia. Ranging in size from a couple of meters to several kilometers across, most are found in areas with active tectonics or high sedimentation rates. These are places where subsurface pressure can build and force a mix of fluids, gases, and sediments to the surface. And these features may not be unique to this planet; scientists think that some muddy mounds in the northern lowlands of Mars may have formed when gas- and liquid-rich sediments spewed out to the surface.
On Earth, Azerbaijan is unusual for its high concentration of mud volcanoes. Geologists have tallied more than 300 in eastern Azerbaijan and offshore in the Caspian Sea, with most of those occurring on land. The region falls within a convergence zone where the Arabian and Eurasian tectonic plates are colliding.
Mud volcano eruptions can be hazardous, with the potential to expel large amounts of material—and even flames—over a short period of time. Azerbaijan’s mud volcanoes are linked to the South Caspian Basin’s vast hydrocarbon system and are known to emit flammable gases such as methane along with the characteristic muddy slurries. It is uncertain if the 2023 Kumani Bank eruption was fiery, but past eruptions of this and other nearby mud volcanoes have sent towers of flame hundreds of meters into the air.
NASA Earth Observatory images by Wanmei Liang, using Landsat data from the U.S. Geological Survey. Story by Lindsey Doermann.
