Saturday 31 May 2014

Flights across Australia disrupted following series of large eruptions on Sangeang Api, Indonesia.

Flights from Australia to Indonesia and Southeast Asia have been severely disrupted and several airports forced to close completely following a series of massive eruptions on Sangeang Api, an island volcano in the Lesser Sunda Islands, Indonesia. The eruptions began on Friday 30 May 2014 and have so far produced three large ash plumes. The first reached a height of between 6 and 15 km and has drifted southeast over Australia towards Alice Springs. The second reached a height of 14 km and is currently over the city of Darwin, and the third has drifted westward and is currently over Bali. 

Ash column over Sangeang Api on Friday 30 May 2014. Sofyan Efendi.

Volcanic ash is extremely hazardous to aircraft in a number of ways. At its most obvious it is opaque, both visually and to radar. Then it is abrasive, ash particles physically scour aircraft, damaging components and frosting windows. However the ash is most dangerous when it is sucked into jet engines, here the high temperatures can melt the tiny silica particles, forming volcanic glass which then clogs engine. When this happens the only hope the aircraft has is to dive sharply, in the hope that cold air passing through the engine during the descent will cause the glass to shatter, allowing the engine to be restarted. Obviously this is a procedure that pilots try to avoid having to perform.

Sangeang Api is a complex volcano comprising two cones, Doro Api and Doro Mantoi, rising to 1949 m and 1795 m above the sea respectively, located on an island roughly 5 km off the northeast coast of West Nusa Tenggara in the Flores Sea. The island has been uninhabited since 1988 when it was abandoned following a series of large eruptions. It is an extremely active volcano, having undergone major eruptions least 19 times since 1512; the first eruption on the island recorded by eyewitnesses.

The location of Sangeang Api. Google Maps.

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).

See also...

The United States Geological Survey recorded a Magnitude 5.2 Earthquake at a depth of 27.2 km, 9 km to the northeast of the city of Kupang on the western (Indonesian) half of the Island of Timor, at...

The Darwin Volcanic Ash Advisory Centre reports an eruption on the island volcano Batu Tara, one of the Lesser Sunda Islands in the Flores Sea, producing a 2.1 km ash column on the morning of Friday...

Six people, including two children have been killed by an eruption on Mount Roketenda on the tiny Indonesian island of Palue (or...

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