Exciting volcanic discovery beneath Panmure basin
SCIENTISTS were abuzz last week as they extracted fresh evidence from the depths of the Panmure basin that pointed to a new volcano sitting beneath the basin sediment.The joint team from Auckland University and the Institute of Geological and Nuclear Sciences (GNS) unearthed over half a ton of material in one drilling that shows a more recent scoria cone sitting inside the older maar volcano which forms Panmure basin. A maar crater results from an explosion but does not create a cone.Dr Graham Leonard, the main scientist supervising last week’s drilling, calls the discovery “very exciting”. It shows the recent volcano has erupted from inside the crater of the first. “It’s all very useful to understanding risk [of volcanoes] in Auckland,” says Dr Leonard. He says knowing the clustering patterns of volcanoes can help predict future eruptions. Dr Ian Smith, a volcanologist from the university’s Institute of Earth Science and Engineering, has been part of the team which has drilled five locations in the last three years, removing long cores 85 millimetres in diameter from the earth. This time they were looking to understand the history of other volcanoes in the Auckland area, but had not anticipated such a discovery. “It was certainly a surprise to us,” says Dr Smith. “The change is we had thought of Auckland volcanoes as being quite simple. Perhaps they’re not as simple as we think.”Currently the scientists have not yet determined whether the new volcano is part of the Panmure event, which took place 28,000 years ago, or is in fact much younger, at about 10,000 years. A younger age would put it closer to the Mt Wellington eruption, a prospect Dr Leonard calls “tantalising”.“It’s very important if it is younger. It would change our picture of the Auckland volcanic field”.Only Rangitoto shows a volcano occurring on the same spot much later.At a second site in the basin where drillers managed to get 44 metres down, the team found 2.6 metres of ash from the eruption that caused Mt Wellington 9200 years ago, an amount that helps confirm that was one of the biggest core-forming eruptions in the Auckland field. It is also the second most recent eruption after Rangitoto.Dr Leonard says the discoveries are timely because March sees the Emergency Management Exercise Ruaumoko taking place across Auckland. Dr Leonard has been advising central and regional governments on the exercise, which Civil Defense calls “a test all-of-nation preparedness for a volcanic eruption in Auckland” .Now more than a dozen scientists, will help with the chemical analysis and evaluation of the data over the following year.
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