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

Dr. Jenni Hopkins is meticulously building the Tephra New Zealand database, a growing collection of volcanic ash samples that spans the last four million years of New Zealand's geological history.

Each sample, collected from various locations across New Zealand, is accompanied by maps and photographs detailing its origin. Initially a mixture of mud, organic material, and small rocks, the volcanic ash is carefully cleaned and sieved to isolate the fine, white-grey dust that Hopkins intends to study.

Her primary goal is to analyze the precise chemical composition of the ash. This analysis will help determine the potential hazards associated with large ash eruptions from New Zealand's active volcanoes. "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," Hopkins notes.

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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.

Even minor ash dispersal, such as from the 2012 Te Maari eruption on Mount Tongariro, caused significant disruptions, including road closures and grounded flights. Beyond physical disruption, the ash's chemistry poses a threat. Following the 1995/96 Ruapehu eruptions, an estimated 2,000 sheep died from fluorosis, a condition caused by consuming fluorine-rich ash.

Hopkins is particularly interested in elements like sulfur, fluorine, chlorine, and heavy metals such as cadmium and arsenic, which can be hazardous to livestock and humans but are challenging to analyze. She uses an electron microprobe to identify elements on the surface of tiny volcanic glass shards, adding the data to the tephra database. However, she acknowledges the difficulty, stating, "That's the hardest part of this research... 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."

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That's the hardest part of this research... 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.