Wednesday 22 December 2021

Eruption on Hunga Ha'apai volcano, Tongo.

The remote Hunga Ha'apai volcano in Tongo erupted on Monday 20 December 2021, producing an ash column 18 km high, and ash-falls across the island group. There are no reports of any casualties associated with this event, however, local authorities are warning people not to collect rainwater for drinking (a common practice in a nation where many communities do not have access to other water sources) until the ash cloud has cleared, due to the dangers of acid rain, which can cause severe health problems. Aircraft were warned to keep away from the islands during the eruption, resulting in the cancellation of at least one flight.

An eruption on the Hunga Ha'apai volcano, seen from Nuku'alofa on Monday 20 December 2021. Mary Lyn Fonua/AFP.

Hunga Ha’apai lies 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 the 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.
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