Natural Disasters in Tonga

4th February 2022

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By Geoffrey Clark

As Tongan communities rebuild after the Hunga-Ha'apai eruption and tsunami, the historical record suggests they are no strangers to these kinds of events. Volcanic activity has a long history in Tonga, including some evidence in the archaeological record and in oral history.

The composition and alignment of Tonga’s islands demonstrates this precarious geographic situation. The Tongan island chain is made up two parallel ridges on the Tonga-Kermadec Subduction Zone. The eastern ridge including the largest inhabited islands is primarily uplifted limestone and the western line is volcanic and highly active, including the islands of Kao, Late and Tofua and numerous underwater volcanoes. This includes the underwater volcano that has been so spectacularly active in recent months.

Among the many accounts of damage and destruction, the home and resort of local archaeologist Shane Egan was destroyed. He had an important collection of Tongan artefacts in a small museum. Egan lived and worked on the beachfront directly facing the volcano and left after the explosion moments before the wave reached land. He estimates the tsunami wave, which swept across the north-western peninsula of Tongatapu, was moving at 650 km an hour.

Tonga1Shane Egan at Kanokupolu

In 2015, sufficient lava and ash built up to join separate parts of the Hunga Ha'apai crater that had already emerged above sea level. As part of an ARC-supported archaeological project in 2018, an ANU and University of Tokyo team made an observational visit and collected ejected pumice. These samples can be matched with pumice deposits in archaeological sites and sediments on the nearby island of Tongatapu (the main island) to determine eruption histories. It is clear through ash deposits that eruptions occurred shortly before people first arrived 2850 years ago and again perhaps 1000 years ago, although this has yet to be confirmed by dating work.

An American team has suggested there may be evidence of a mega-tsunami 500 years ago, through work on coastal deposits, research published in the weeks before the January event (Lavigne et al. 2021, https://doi.org/10.3389/feart.2021.748755).

In traditional culture, earthquakes were caused by the restless activity of the god Maui who supports the earth. Early 19th century observations record a ritual practice of local people hitting the ground and imploring Maui to stop the movement.

Tonga is an important place for the study of major human dispersals across the Pacific, as one of the end points of the Lapita expansion 3,000 years ago, that along with Samoa, was where Polynesian migration began. The Lapita movement, tracked via the distinct pottery decoration, carried through from Papua New Guinea eastward through Vanuatu New Caledonia and Fiji to Tonga and Samoa. From there, Lapita culture developed into a distinctly Polynesian form that around 1,000 years ago spread through the east Pacific including to Hawaii, Aotearoa-New Zealand, Rapa Nui-Easter Island.

ANU archaeology has had a long presence in Tonga working with the local community and government, stretching back to the 1950s when Jack Golson and Wal Ambrose first worked on Tongatapu. Current work in ANH investigates the transition from Lapita to early Polynesian culture, including the impacts of sea-level change. Another project investigates the influence of the Tui Tonga dynasty, which placed Tonga at the centre of a widespread and influential maritime empire. The research benefits from the expertise and involvement of the Lapaha community, the Tonga Government's Division of Culture, and the Tonga Traditions Committee.

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