Saturday 18 February 2017

Ongoing eruptions on Barren Island.

A group of scientists from India's National Institute of Oceanography has reported observing eruptions on Barren Island Volcano in the Andaman Islands. The scientists visited the island on 23 and 26 January 2017 onboard the Research Vessel Sindhu Sankalp, in order to collect marine sediment samples. They witnessed a series of small strombolian-type eruptive episodes, each lasting about 5-10 minutes, with ash and lava being thrown from the crater of the volcano and clouds of smoke around its summit. Marine sediments collected near the island were found to contain black pyroclastic sediments associated with recent eruptions. The scientists did not land on the island itself as it was deemed unsafe.

Eruption on Barren Island in January 2017. National Institute of Oceanography.

Barren Island is an uninhabited volcanic island belonging officially to India's Andaman Islands (making it India's only active volcano), though it is about 100 km to the east of the main Andaman Island group and about 450 km west of the coast of southern Myanmar. The island is about 3 km in diameter and rises 354 m above sea level. It is the only active volcano in the region, though it forms part of a group with a number of dormant volcanoes including Narcondam Island and Alcock and Sewell seamounts.

 The approximate location of Barren Island. Google Maps.

The volcanoes sit on the Burma (or Burmese) Plate, a small tectonic plate underlying the Andaman Islands, part of the eastern Indian Ocean and the western part of Sumatra. To the west of the Andaman Islands this plate is being subducted beneath the Indian Plate, but to the east the situation is more complex. The Burma Plate is being pushed northward relative to the Eurasia and the Sunda Plate (which underlies eastern Sumatra, Java, southern Southeast Asia, most of Borneo and the western Philippines) by the northward movement of the Indian Plate, but there is an area of seafloor spreading beneath the Andaman Sea (separating the Andaman Islands from Southeast Asia), which in turn causes stresses within the Burma Plate, leading to a zone of faulting upon which the volcanic islands and seamounts are situated.

 (Left) The movement of the Burma and surrounding plates. Sheth et al. (2011) (Right) Tectonic stresses within and around the Burma Plate. Renjith (2013).

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