RV Tangaroa voyage update
Tonga’s Hunga Tonga - Hunga Ha’apai volcano (HT-HH), erupted violently on January 15th, 2022. Our crew is on site to study the changes this major event has caused to the surrounding area.
23 April 2022
Tangaroa has just arrived north of HT-HH to deploy the glider. The launch was successful and, after some shallow test dives, the instrument was sent on its first transect. A CTD (Conductivity Temperature Depth profiler) with water sample rosette was also deployed to collect water samples used to calibrate the glider’s sensors.
Just north of Hunga Ha’apai, we passed through a line of surface biological material, extending between the two islands. A plankton net was deployed to sample the brown-green material composed of little spheres. This material has been retained for later identification.
Later, the Deep Towed Imaging System (DTIS) was deployed on the erosional channel extending north-west from the caldera. The images show steep drop-offs, dunes, and large volcanic rocks amongst fine-grained sediment.
That evening, we focused on two small features on the north-eastern side of the outer flanks of HT-HH to do rock dredges and take more images with the DTIS. One of the features was a small hill, on which we observed sea pens and glass sponges growing on the reverse slope, away from HT-HH. This reverse slope appears to have provided protection to the benthic life following the volcanic eruption.
We finished the day with another DTIS tow on a site previously sampled with a rock dredge, located on the bottom slopes of HT-HH, to the south of the caldera and close to the valley where the domestic communications cable ran. The imagery showed fine sand and mud, with small gravel stones scattered on the seafloor.
