RV Tangaroa voyage update
Tangaroa has arrived at its next site, close to the Hunga Tonga - Hunga Ha’apai volcano (HT-HH).
26 April 2022
It was our last day in the slopes of HT-HH. The weather was glorious with no wind and blue skies. We were also greeted with the view of the volcano of Tofua island, to the north of HT-HH, emitting thick plumes of steam.
Over the last 24 hours, we have gone from the deep seafloor at 2,300 m to the shallow slopes of the island of Tongatapu, located to the south-east of HT-HH, and have sampled at our third site that will be used to measure the thickness and composition of ash on the seafloor after the violent eruption that occurred on the 15th of January.
On the northern edge of the caldera, we made two CTD (Conductivity Temperature Depth) and water sample rosette deployments. The indications from our other CTD casts suggests the sea water in the caldera is being affected by volcanic heating, and we are targeting a location where this water flows out to the open ocean.
On the south side of the HT-HH summit, we undertook another rock dredge on a line of small (~50 m high) peaks that radiate out from the caldera. The bathymetry collected by the multibeam echo sounder indicated changes in the shape of the seafloor around this area. We were targeting not just the rocks erupted in the recent explosion, but also rocks from older eruptions to help us tell the story of HT-HH’s past.
We left HT-HH behind, as we extended the seafloor mapping with the multibeam to the northern and eastern areas to understand the changes have occurred in the area since the eruption.
Overnight, Tangaroa started to work a series of sites to the south-east of HT-HH, heading toward Nuku’alofa, whith the intention of assessing changes in ash thickness as we move away from the volcano. This information can be linked to the measurements of ash on Tongatapu and help build a better understanding of the atmospheric distribution of the ash cloud.
