The Geological Survey of India (GSI) announced that mud samples collected from the only active mud volcano in India, located at Baratang in the Andaman and Nicobar Islands, date back approximately 23 million years to the Oligocene epoch. This finding emerged following a site visit on October 8-9, which assessed a mud eruption that had been reported on October 2.
According to GSI”s Deputy Director General, Santanu Bhattacharjee, the lithoclasts ejected from the volcano”s crater were identified as sandstone and shale from the Mithakari Group, a geological formation from this era. The Oligocene epoch, which lasted from around 33.9 to 23 million years ago, is noted for significant ecological changes, including the expansion of grasslands and the emergence of modern mammal species such as elephants, cats, and dogs.
“We collected mud samples during our visit, confirming their Oligocene age,” Bhattacharjee stated in an interview with PTI. He described the eruption site as having four clusters of mud volcanoes, each consisting of several small vents. The current eruption area has expanded significantly to about 500 square meters, with a height of around 2 meters at its center, a notable increase from previous measurements of 100 square meters and a height of one meter.
All observed vent clusters were continuously releasing liquid mud and gases. The temperature of the mud ranged between 29.3°C and 30.07°C, with a pH level between 8.0 and 8.3, indicating the weakly alkaline nature of the mud fluid. Additionally, a blackish oily sheen was noted at several vents, appearing as thin layers on the surface of the muddy material.
Regarding the cause of the eruption, Bhattacharjee suggested multiple contributing factors, including the diapiric movement of over-pressurized shale layers, rapid subsidence, lateral tectonic compression, and hydrocarbon generation in deeper subsurface areas. Fluid expulsion from depth along deep-seated fractures or faults may also play a role.
The GSI has advised the Andaman and Nicobar administration to limit public access to the eruption site and construct a viewpoint to ensure safety. Bhattacharjee emphasized the importance of reinforcing fencing and placing hazard signage to educate the public about the unpredictable nature of mud eruptions, recommending that all other access points remain closed except for the designated viewpoint.
