Tuesday, 13 January 2015

Eruption on Hunga Ha’apai.

Flights to and from New Zealand have been disrupted following an eruption on Hunga Ha’apai, a submarine volcano in Tonga, on Monday 12 December 2015, producing an ash column 4500 m high and discolouring the sea red with ash, according to the Wellington Volcanic Ash Advisory Centre. The volcano is reported to have become active on 20 December 2014, according to the Institute of Geological & Nuclear Science in New Zealand, but this is the first major disruption caused by the volcano this year. The crater of Hunga Ha’apai lies beneath the sea, but two small islands, Hunga Tonga and Hunga Ha’apai, which form part of the crater rim, reach 149 m and 128 m above the sea respectively.

 The ash coloumn over Hunga Ha'apai on 13 January 2014. Radio Live/Twitter.

Hunga Ha’apai ies on the Tonga/Kermadec Ridge, and is fed by the subduction of the Pacific Plate beneath the  Australian Plate along the Kermadec/Tonga Trench. As the Pacific Plate sinks into the Earth it is warmed by a combination of heat from friction with the overlying Australian Plate, and heat from the planets interior. This leads to partial melting of the Pacific Plate, with some of the melted material rising through the overlying Australian Plate as magma, fuelling the volcanos of the Kermadec/Tonga Ridge.

Diagram showing subduction along the Tonga Trench, and how this feeds the volcanoes of the Tonga Volcanic Arc. York University.

See also...

http://sciencythoughts.blogspot.co.uk/2012/08/the-biology-of-pumice-rafts.htmlThe biology of pumice rafts.                                Pumice is a volcanic rock, produced by the rapid cooling of gas rich lava from submarine eruptions, or high-pressure eruptions on land. The rapid cooling traps bubbles of gas within the rock, creating a very light material that will often float on water. Submarine volcanic eruptions can produce vast mats of...
http://sciencythoughts.blogspot.co.uk/2012/08/pumice-raft-suggests-eruption-from.htmlPumice raft suggests eruption from Mount Monowai.                                                                    On Thursday 9 August 2012 the Royal New Zealand Air Force spotted a raft of pumice-stone (volcanic rock filled with gas bubbles that floats on water) covering an area nearly 26 000 km², roughly 1000 km north  of North Island, in the Kermadec Islands, a New Zealand possession. This discovery was later confirmed by the Royal New Zealand Navy ship HMNZS Canterbury...
http://sciencythoughts.blogspot.co.uk/2011/07/earthquake-in-kermadec-islands-triggers.htmlEarthquake in the Kermadec Islands triggers tsunami alert.                                                                                                The Kermadec Islands are the northernmost outpost of New Zealand, situated 650 km northeast of North Island, and 550 km southwest of Tonga. They are a Volcanic Island Arc, which is to say a group of islands that sits on a convergent plate margin (in this case the one where the Pacific Plate is being subducted beneath the Australian) and are formed entirely by volcanic activity. This volcanic activity occurs when rocks from the subducted plate melt as...

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