The Hunga Tonga-Hunga Ha’apai volcano, which erupted catastrophically on January 15, 2022, makes a surprising and unexpected appearance months later.

Scientists from New Zealand’s National Institute for Water and Atmospheric Research say that the new study results from the record-breaking Tongan volcanic eruption are “surprising and unexpected”.

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

Researchers thought that the volcano would have changed a lot because of how powerful the explosion was, but it was mostly the same.

Up to seven cubic kilometers of shifted material was documented by NIWA scientists – the equivalent of five Wellington Harbours or three million Olympic-sized swimming pools – but there is likely more to come. Tonga’s broken domestic internet cable, which stopped communication, is now buried 30 meters deep in ash and sediment.

Kevin Mackay, a marine geologist with NIWA, says he was utterly taken aback by what they observed at first.

“With an explosion that violent – the biggest ever recorded – you would expect that the whole volcano would have been obliterated, but it wasn’t. While the volcano appeared intact, the seafloor showed some dramatic effects from the eruption. There is fine sandy mud and deep ash ripples as far as 50 kilometres away from the volcano, with gouged valleys and huge piles of sediment.”

The crew also looked into the effects on the ecology. Although the volcano lacks biodiversity, there are elements as close as 15 kilometers away that have abundant and diversified populations of fish and other creatures. Scientists believe they survived impact by being out of the course of the eruption flow or far enough away to avoid thick ashfall.

According to NIWA marine biologist Dr. Malcolm Clark, having robust life around is a good sign.

“Although the seafloor on the volcano is largely barren, surrounding seamounts have pockets of normal biodiversity, such as corals, sponges, starfish, and mussels, indicating the resilience of such marine ecosystems and giving some hope for recovery. More work needs to be done before we can be confident of how the ecosystem will respond, but these surviving animal communities indicate what kind of life may repopulate HT-HH. The sites sampled during the voyage give us a baseline for monitoring recovery in the future.”

Temperature, nutrients, and oxygen concentration were among the physical and chemical parameters of the water column studied by NIWA.

According to preliminary data, the water column is still recovering, and some flying ash has not yet settled completely on the seafloor. A strong ash layer detected in the upper water column around the volcano suggests that the volcano may still be erupting.

The persistence of ash in the water column, according to NIWA biogeochemist Dr. Sarah Seabrook, has a variety of effects on the ocean ecology.

“In the immediate aftermath of an eruption, volcanic ash fertilises microscopic ocean algae thanks to the ash’s concentration of nutrients and trace metals – in this case, there was a bloom of life so big that we could see it from space.”

“However, the unexpected persistence of the ash in the water column is creating prolonged impacts. For example, spikes in volcanic ash were coupled to the appearance of oxygen minimum zones – where oxygen levels in the water are at their lowest – which could have implications for important services provided by the ocean, such as food production and carbon sequestration.”

Hundreds of samples were taken throughout the voyage, including seabed cores, numerous corals, and 250 kg of rock, some of which were newly produced due to the eruption.

The TESMaP project offers a once-in-a-lifetime opportunity to investigate the consequences of an undersea volcano, which has far-reaching ramifications for nations and ecosystems living near these natural wonders.

The mission also shed light on what would happen to the broken domestic internet cable, with strong indications that it will need to be completely replaced.

Image Credit: Getty

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