“Ghost” island Kumani Bank forms in Caspian Sea following mud volcano eruption

A mud volcano eruption at Kumani Bank, approximately 20 km (12.4 miles) from Azerbaijan’s coast, resulted in the formation of a new island in early February 2023. The island’s sudden appearance is revealed in satellite images, measuring around 400 m (1 310 feet) across, though no official reports were made about the event.

Mud volcano specialist Dr. Mark Tingay of the University of Adelaide recently expressed surprise that such a phenomenon went largely undocumented despite the island’s proximity to Baku, Azerbaijan’s capital.

Tingay described the eruption as part of a phenomenon known as “emergent” or “ghost” islands. “Kumani Bank is not normally visible, with its crest being just a few meters below sea level,” Tingay explained. “However, a violent eruption can release enough material to push the crest of the mud volcano above the surface, creating a new island.”

Kumani Bank mud volcano, also known as Chigil-Deniz in various books and journal articles, has erupted numerous times, with documented island formations occurring in 1861, 1927, 1950, and as recently as 2001. In each case, the islands persisted only briefly before eroding back underwater.

“It’s quite famous for being a suddenly appearing island – it’s mentioned in numerous geology texts from back to the 1800s,” Tingay said for The Watchers.

The crest of the Kumani Bank mud volcano typically sits around 5 m (16.4 feet) below the sea surface. During a significant eruption, however, a large volume of material is expelled rapidly, causing the crest to rise above sea level and form an island. Due to the weak and muddy composition of this material, the newly formed island erodes quickly, often disappearing within a few months and almost always within two years.

“These eruptions are short, often lasting minutes to hours, but incredibly violent, releasing over 1 million m³ [35.3 million ft³] of mud,” Tingay said. He compared the phenomenon to the 2021 eruption of nearby Dashli Island, where flames up to 500 – 1 000 m (1 600 – 3 300 feet) high were recorded, though no flames were associated with Kumani Bank’s recent eruption.

Tingay noted the unusual lack of attention the new island received. “You’d think that some fisherman would have noticed and posted some photos. Or the Azeri Coast Guard would’ve reported it or something,” he said.

“A new 10 ha (25 acres) island just appears one day, and no one even cares… Well, I care.”

In the Sentinel-2 satellite images, the island is visible on February 4, 2023, but is absent in the earlier image from January 31, 2023, placing the formation of this island within those few days.

Satellite data from October 2024 showed that Kumani Bank had already begun to erode, with the island now reduced to less than a quarter of its February 2023 size.

“We call these ‘peek-a-boo’ islands because they appear very suddenly but are then rapidly washed away by the waves and slip back beneath the seas, disappearing within a few months or years.”

While such islands are rare, the transient nature of mud volcanoes can make them challenging to document. Tingay, who has studied similar formations in locations from Pakistan to Colombia, finds the phenomenon remarkable.

“I find it amazing that an island, 400 m [1 310 feet] wide, can suddenly appear within the space of a few hours,” he said, pointing to how easily such events can be missed even in the modern information age.

Despite its proximity to populated areas and high-traffic waters, the sudden appearance of Kumani Bank remains a curious, largely undocumented occurrence.

The island, which had been submerged prior to 2023, is expected to vanish again soon due to ongoing erosion from the Caspian Sea’s waves, reinforcing its “ghost” island status in geological records. That is if no new eruption takes place to replenish the material and once again elevate the crest above sea level.

Without such volcanic activity, the weak, muddy sediment will continue to erode, likely causing the island to disappear back beneath the waves within a few months.

Teo Blašković

I'm a dedicated researcher, journalist, and editor at The Watchers. With over 20 years of experience in the media industry, I specialize in hard science news, focusing on extreme weather, seismic and volcanic activity, space weather, and astronomy, including near-Earth objects and planetary defense strategies. You can reach me at teo /at/ watchers.news.

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