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Mt Tongariro erupts!

August 2012

Tongariro Erupts!
Mt Tongariro following the eruption of the 6 August 2012

When Mt Tongariro (Central North Island, New Zealand) erupted on the 6 August 2012 at 11.50 pm, researchers from Volcanic Risk Solutions were quick to respond. The first teams left Massey University in Palmerston North at 2am on the 7 August, with equipment to collect ash and take other measurements. The teams took measurements and collected ash from the eruption at as many locations as possible, along the sides of state highways, from vegetation and from parked vehicles, with teams driving out to as far as Napier to make sure the full extent of the ash cloud from the eruption was sampled. The collected ash was taken back to Massey University in Palmerston North for analysis in order to gain a better understanding of the eruption and the likelihood of future activity. Ash was also sent to Massey University by members of the public.

A priority was to analyse the leachate chemicals present in the ash to ascertain the risk it posed to the communities surrounding the volcano. Ash picks up water-soluble chemicals as it is erupted and these chemicals can leach into soil, waterways and drinking water supplies, potentially contaminating them. This leachate work was carried out in collaboration with Massey University’s Fertilizer and Lime Research Centre, the University of Canterbury, and Landcare Research Ltd.

Another priority post-eruption was to find out whether the eruption involved magma or was hydrothermal in nature, which would help assess the future risk of eruption. This involved detailed analysis of particles of ash. Fine fractions of the ash were analysed by optical microscope and also by Scanning Electron Microscope to look for volcanic glass (a sign that magma was involved in the eruption), using the facilities of the Manawatu Microscopy and Imaging Centre. Ash samples were also analysed by electron microprobe (in collaboration with the University of Otago and Victoria University at Wellington) to further check for signs of volcanic glass. The grain size of the ash was measured as well, which also gave researchers information about the type of eruption.

The eruption on the 6 August 2012 produced no lahars, but a debris flow near the vents was observed from aerial photographs following the eruption. As the danger subsided after the eruption, scientists were allowed closer to the vents and the debris flow was examined and sampled. A GPS survey was also carried out.

Researchers from Volcanic Risk Solutions have also been involved in refining the hazard maps for the Tongariro area following the eruption. Computer simulations, based on research of the Volcanic Risk Solutions group, were used to define hazard zones, and these were used as the basis for a map of the most hazardous regions of Tongariro National Park in the event of further volcanic activity.

Natalia Ash Collection
Natalia Pardo samples ash from the eruption of Mt Tongariro
Hazard map
Hazard map of the Tongariro area after the August 2012 eruption