Saturday 19 May 2012

Eruption on Mount Sirung.

On 8 May 2012 a series of loud rumblings were heard from Mount Sirung, on Pantur Island in the Alor Archipelago, part of the Sunda Islands (Indonesia). These were followed by a three hour ash eruption and incandescence (glowing) over the crater. The ash cloud rose 3.5 km above the summit, and drifted to the north, leaving ash deposits up to 4 mm thick on the northern side of the volcano. Smaller ash plumes (30-40 m) were observed over the next three days, and the Pusat Vulkanologi Dan Mitigasi Bencana Geologi issued a warning for people not to approach within 2.5 km of the volcano. On 12 May the  Darwin Volcanic Ash Advisory Centre reported an ash cloud rising 3 km over the island and drifting to the southwest.

The location of Mount Sirung.

Mount Sirung is a complex volcano at the southern tip of Pantar Island. The current active crater is the northeasternmost of a 14 km chain of craters. It rises 862 m above sea level, and has a caldera 2 km wide with (usually) a sulphurous lake in the bottom.

The volcano last erupted in 1970 (a reported eruption on Australian TV in 2004 was erroneous). The volcano is thought to have erupted 9 times in the twentieth century, with one eruption, in June 1953, causing 5 fatalities.

The crater-lake in the caldera of Mount Sirung. Vulkaner.

The Lesser Sunda Islands are located on the northern part of the Timor Microplate. This is trapped between the converging Eurasian and Australian Plates, both of which are being subducted beneath it. In the south the Australian Plate is passing under the island of Timor, with material from the subducted plate melted by the friction and the heat of the Earth's interior rising through the Timor Plate to feed the volcanoes of the island. In the north the Eurasian Plate is being subducted in the same way, feeding the volcanoes there.

The subduction zones beneath the Timor Microplate. Hamson (2004).

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