GSNZ Wellington branch talk

Hunga Tonga Hunga Ha’apai (HTHH), one of 22 volcanoes in the waters around the Kingdom of Tonga, erupted violently on 15^th January 2022.  This eruption triggered shock waves through the atmosphere and generated a tsunami across the Pacific Ocean.  

No part of the caldera of the volcano remained above water following the eruption, and the islands of Hunga Tonga and Hunga Ha'apai were vastly reduced in size.  During an oceanographic survey 3 months after the eruption, we assessed the impacts of this eruption on the surrounding ocean environment, from underwater topography to ecosystem structure and function.  While the HTHH edifice was largely intact, erosional channels were identified radiating out from the summit caldera indicating turbulent pyroclastic density flows which are supported by our modelling.  

At least 6 km³ of material was deposited on the seafloor in areas downstream of these pyroclastic flows, and 50 cm of fine ash deposition was observed on the seafloor in some areas.  Mid water volcanic ash layers north of the HTHH caldera were identified, which indicates on going venting from the volcano. Significant seafloor ecosystem impacts were found throughout much of the region, with little signs of life remaining on the flank of the volcano and along the deeper slope.

This study is a rare account of the initial impact of a large-scale eruption which can be used to better understand volcanic risks to the ocean environment in the future.

This talk is being presented in person at Victoria University of Wellington but you can also join using Zoom. Members of the Wellington branch will automatically be sent the link (although we'd love to see you there). If you are not in the Wellington branch and would like to receive the Zoom link please contact Wellington@gsnz.org.nz no later than 3pm on 17 May and you will be added to the distribution list for this talk.