Volcanic Fingerprints

Volcanic ash has a chemical signature that is unique to its source, says postdoctoral researcher Dr Jenni Hopkins, who is using this trait to reconstruct the eruption history of the Auckland volcanic field.

This technique—known as fingerprinting—has allowed the history of the volcanic field to be determined, including the timing, size and location of the past eruptions.

Dr Hopkins, a volcanic geochemist who completed her PhD in the School of Geography, Environment and Earth Sciences, collaborated with NIWA, GNS and the University of Auckland on the research, which was part of a larger project called DEVORA (determining volcanic risk in Auckland).

“As Auckland is the central hub for New Zealand businesses, and home to a quarter of New Zealand’s population, our work is critically important for preparing us for the next eruption,” says Dr Hopkins.

“DEVORA is a multi-agency, transdisciplinary research group working towards an improved assessment of the volcanic hazard and risk posed to the Auckland Metropolitan area.

“The Auckland volcanic field isn’t like Ruapehu or Taranaki that formed over a long period of time from a series of eruptions. Rather, each one of the volcanoes in Auckland is formed from a single eruption.

“The eruptions in Auckland are so small that they often don’t have enough magma to form cones and will commonly just form explosion craters, where the upwelling magma interacts with ground water.

“And because there has only been one eruption per volcano, each volcano is responsible for a single layer of volcanic ash found within the craters. So we can drill sediment cores, extract the volcanic ash, and use the size and location of the ash to tell us about the timing and size of the eruption.”

Dr Hopkins is using this information on past eruptions to create models and simulations to help predict where and when future eruptions are likely to happen, who they will impact, and for how long.

“By correlating the ash to the volcanos it came from we can reconstruct the history, and use the characteristics of this history to try to predict the characteristics of future eruptions.”