India’s unique active mud volcano, nestled in Baratang in the Andaman and Nicobar Islands, holds a deep secret: its origins stretch back an astonishing 23 million years, to the ancient Oligocene epoch. This remarkable discovery comes from samples recently analyzed by the Geological Survey of India (GSI).
Further examination revealed that the rock fragments, or lithoclasts, expelled from the volcano’s crater are primarily composed of sandstone and shale from the Mithakari Group, precisely matching this primeval geological era.
For context, the Oligocene epoch, spanning roughly 33.9 to 23 million years ago, was a pivotal time in Earth’s history. It witnessed significant environmental shifts, including the widespread emergence of grasslands, a period of global cooling, and the fascinating evolution of many modern mammal lineages – even the earliest ancestors of today’s elephants, cats, and dogs.
Santanu Bhattacharjee, Deputy Director General of the GSI, confirmed their team’s visit to the site on October 8-9, following a mud eruption reported on October 2. ‘We collected mud samples and confirmed their Oligocene age,’ he stated.
Scientists observed four distinct clusters of mud volcanoes, each featuring numerous small vents. These clusters now span approximately 500 square meters and reach about 2 meters in height at their core. This represents a substantial expansion from previous records, which noted the eruption site covering only 100 square meters and reaching a meter in height. All observed vents were actively releasing liquid mud and gases.
Bhattacharjee also noted the mud volcanoes’ surface temperatures, which ranged from a mild 29.3°C to 30.07°C. The mud fluid exhibited a pH level between 8.0 and 8.3, characterizing it as weakly alkaline.
Intriguingly, some vents displayed a thin, oily blackish sheen on the surface of the muddy discharge.
Regarding the precise cause of these eruptions, Mr. Bhattacharjee explained that multiple geological processes could be at play.
These potential causes include the diapiric movement of highly pressurized shale layers beneath the surface, triggered by the weight of terrestrial sediments, sudden land subsidence, or intense lateral tectonic compression. Other factors could be the generation of hydrocarbons deep underground, leading to the expulsion of fluids through ancient fractures and faults.
In light of these active phenomena, the GSI has advised the Andaman and Nicobar administration to implement safety measures. These include restricting public access to the immediate vicinity and establishing a designated viewpoint at a safe distance from the mud vent clusters.
Furthermore, Mr. Bhattacharjee emphasized the need for reinforced fencing and clear hazard signage to educate the public about the unpredictable nature of violent mud eruptions. All access routes other than the designated viewpoint are to remain closed.