Our Changing World: Analysing ash and studying Vanuatu’s volcanoes

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The stack of red plastic boxes in Dr Jenni Hopkins' office hold an important, growing collection.

The Tephra New Zealand database begins as bags of volcanic ash, collected from eruptions spanning recent times, back to about four million years ago.

Taken from all over New Zealand, the bagged samples come with maps and photos of where they were gathered from. Each sample begins as a jumble of things - mud, organic material, small rocks, plus the volcanic ash that Jenni wants to study.

When cleaned and sieved the ash, or tephra, looks like fine, white-grey dust. And it's this concentrated sample that Jenni will use to figure out exactly what elements are in there.

The hazards of ash

Jenni wants to work out what the potential hazards might be if one of our active volcanoes releases a lot of ash in a future eruption. "Because we haven't had a really big ash eruption in living memory, it's kind of something that people don't necessarily think about", she says.

But even the small amount of ash dispersed from the 2012 Te Maari, Mount Tongariro eruption caused issues - roads were closed and airplanes grounded.

And beyond its disruptive physical presence, the chemistry of the ash could be an issue too. Following the 1995/96 Ruapehu series of eruptions an estimated 2000 sheep in the area died due to fluorosis - a result of the livestock eating ash rich in fluorine.

Our Changing World has covered research into Whakaari and Ruapehu to try to understand their style and patterns of eruptions. Plus the show has visited Auckland's underground lava caves and learned how the Tongan volcano resulted in a world-wide tsunami.

This is what Jenni is particularly interested in - chemical elements that might be hazardous to livestock and humans, but that tend to be a bit harder to analyse. Things like sulphur, fluorine, chlorine and heavy metals such as cadmium and arsenic.

To do this, Jenni is analysing ash samples from recent and past eruptions to work out exactly what elements are present. Once she has a concentrated volcanic ash sample, she suspends it in an epoxy disc and feeds in into a piece of equipment called an electron microprobe. The microprobe which uses a focused beam of electrons to identify what elements are on the surface of tiny shards of the volcanic glass, giving Jenni a readout that can be added to the tephra database.

But, unfortunately, it's not as simple as that. Some of the elements she is interested in can interact readily with, or dissolve in, water - this means that they leach out of the ash over time, making her task of predicting the chemistry of a future eruption more difficult.

"That's the hardest part of this research," says Jenni, "So an aspect of the science that I'm doing is trying to work out what is missing and how do we find it. That could be through sampling existing eruptions or looking at gas chemistry of what's going on as an eruption's occurring. So there's a range of ways that we're hoping to develop that kind of unknown."

To help with sampling at active volcanoes, Jenni is looking to a colleague who is just down the hallway, someone who has recently lead a project to measure the gas chemistry of a chain of active volcanoes in the Pacific.

The Waka Lab project

Dr Ian Schipper's office is also stacked with samples - white filter paper in small, sealed bags, little tubes with clear liquid inside. Analysing these samples is on the to-do list.

"You go out on a six-week expedition and collect enough data and enough samples to keep you busy for six years!" says Ian.

These samples come from an oceanic arc of volcanoes - a chain that runs from Vanuatu up into the eastern Solomon Islands and contains five of the top 10 most active volcanoes in the world, according to satellite measurements.

The technical and logistical challenges of taking on-site gas measurements and samples of these volcanoes was such that some had never been collected before, says Ian.

"You need to travel by ocean to get there but that's not straightforward either, or actually it is but it didn't seem straightforward, to a Western science perspective where most work at sea, for geologic purposes, is done using these giant diesel-powered international consortiums, that cost millions of dollars and are also quite impractical."

The answer, says Ian, had been solved millenia ago by Polynesian and Melaneisan peoples. "Waka are absolutely perfect vessels for this. They are designed for this, to move people and goods across stretches of open ocean, but also to navigate shallow waters and to do so sustainably as well."

And so he teamed up with waka voyaging trust, Te Toki Waka Hauroa, and the project became known as the Waka Lab.

Having faced multiple setbacks across a number of years, including one waka being struck by lightning, in 2025 the team undertook a six-week expedition to sample at multiple volcanoes across Vanuatu and the Solomon Islands.

This involved working with local government agencies as well as the communities that live with and have deep knowledge of these active volcanoes, says Ian.

While the project is officially finished now and the next step is sample analysis, Ian is hoping that they can find a way to maintain these relationships, and continue to sample the volcanoes to learn more about their unique chemistry, as well as the 'family dynamics' of the Oceanic arc as a whole.

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