Surprising Findings from Hunga Tonga Expedition

New findings from the record-breaking Tongan volcanic eruption are “surprising and unexpected,” said scientists from New Zealand’s National Institute for Water and Atmospheric Research (NIWA).

NIWA’s research vessel, RV Tangaroa, has returned from a month-long expedition as part of The Nippon Foundation-funded Tonga Eruption Seabed Mapping Project (TESMaP), where scientists were studying the effects of January’s eruption of Hunga Tonga–Hunga Ha’apai (HT – HH).

Due to the power of the explosion, researchers expected to find dramatic changes to the volcano but instead found it largely intact.

The research is also supported by The Nippon Foundation-GEBCO Seabed 2030 Project which aims to map the world’s ocean floor by 2030. NIWA mapped 22,000 sq. km of the surrounding seafloor, which showed changes covering an area of 8,000 sq. km.

NIWA scientists recorded up to 7 cubic km of displaced material, and there is likely more yet to be seen. Tonga’s domestic internet cable that was broken and cut off communication is buried under 30 m of ash and sediment.

The team also studied impacts on the ecosystem. The volcano is devoid of biology, but remarkably there are features as close as 15 km away that still have abundant and diverse populations of fish and other animals. Scientists speculate that they escaped impact by being out of the eruption flow’s pathway or far enough away to avoid thick ash fall.

Preliminary data show that the water column is still recovering, and some airborne ash is yet to completely settle on the seafloor. There is also evidence that the volcano may still be erupting, with a dense ash layer found in the upper water column near the volcano.

The second part of the TESMaP mission will see the caldera mapped by a USV built by SEA-KIT International. The caldera was unable to be surveyed during NIWA’s voyage because of safety reasons. The unmanned part of the research mission to study the caldera is expected to be completed in mid-July. 

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