A recent discovery by the Geological Survey of India (GSI) has shed new light on India’s unique active mud volcano located in Baratang, within the picturesque Andaman and Nicobar Islands. Samples collected from the site confirm that its geological material dates back an astonishing 23 million years, placing its origin firmly in the Oligocene age.
GSI officials revealed that the lithoclasts – rock fragments ejected from the volcano’s crater – are primarily composed of sandstone and shale from the Mithakari Group, a formation characteristic of this ancient geological period.
For context, the Oligocene epoch, spanning from approximately 33.9 to 23 million years ago, was a pivotal time in Earth’s history. It was characterized by significant global cooling, the widespread expansion of grasslands, and the diversification and evolution of many modern mammal species, including the earliest forms of elephants, cats, and dogs.
Santanu Bhattacharjee, the Deputy Director General of GSI, elaborated on the findings, stating, “We visited the site on October 8-9 to assess the mud eruption reported on October 2. Our analysis of the collected mud samples conclusively showed they belonged to the Oligocene age.”
Further observations at the site revealed a dynamic geological landscape. A total of four distinct clusters of mud volcanoes, featuring numerous small vents, were identified. These clusters span an area of approximately 500 square meters, with the central points rising about 2 meters high. This represents a significant expansion compared to previous records, which noted an area of 100 square meters and a height of just one meter. All these vents were continuously discharging liquid mud and various gases.
Mr. Bhattacharjee also noted the consistent environmental characteristics of the mud volcanoes, with surface temperatures ranging from 29.3°C to 30.07°C and a pH level between 8.0 and 8.3, indicating a mildly alkaline mud fluid. Interestingly, an oily, blackish sheen was observed as thin layers on the surface of the muddy material emanating from some vents.
Addressing the underlying causes of these eruptions, Mr. Bhattacharjee explained that several geological processes could be at play. These include the diapiric movement of over-pressured subsurface shale layers, triggered by the weight of terrigenous sediments, rapid geological subsidence, or intense lateral tectonic compression. Additionally, the generation of hydrocarbons deep within the Earth’s crust and the expulsion of fluids along deep-seated fractures or faults could also contribute to this fascinating phenomenon.
In response to these findings and the ongoing activity, the GSI has urged the Andaman and Nicobar administration to implement safety measures. These recommendations include restricting public access to the immediate vicinity of the eruption site and constructing a designated viewpoint at a safe distance from the active vent clusters. Furthermore, strengthening existing fencing and installing clear hazard signage are crucial steps to educate the public about the unpredictable nature of violent mud eruptions and to ensure visitor safety by limiting access to areas beyond the designated viewpoint.