• Pink pumice key to revealing explosive p

    From ScienceDaily@1:317/3 to All on Tue Feb 8 21:30:42 2022
    Pink pumice key to revealing explosive power of underwater volcanic
    eruptions

    Date:
    February 8, 2022
    Source:
    Queensland University of Technology
    Summary:
    The presence of pink pumice in the giant pumice raft of the 2012
    Havre that drifted across the southwest Pacific Ocean has led
    researchers to recognize the immense power of underwater volcanic
    eruptions.



    FULL STORY ==========================================================================
    In research published in the Nature portfolio journal Communications
    Earth and Environment,the researchers including Professor Scott Bryan,
    Dr Michael Jones and PhD candidate Joseph Knafelc, were intrigued by the occurrence of pink pumice within the massive pumice raft that resulted
    from the Havre 2012 deep- sea eruption.


    ==========================================================================
    The publication of the new research comes after the recent dramatic
    explosion of the Hunga Tonga Hunga Ha'apai volcano in Tonga, about 1200
    km north of the Havre volcano, which has sharply brought the world's
    attention to the explosive potential and hazards associated with submarine eruptions.

    Professor Bryan, who has been studying pumice rafts for more than 20
    years, said the pink pumice produced in the 2012 Havre eruption revealed insights into how magma can shoot out and up from underwater volcanoes.

    "Unlike Hunga Tonga-Hunga Ha'apai, Havre is in a much more remote
    location. Its summit is 900m below sea level, and the nearest populated
    areas are around 800km away on the North Island of New Zealand," Professor Bryan said.

    When the volcano erupted in 2012, there was no one to see it happen. But
    the colour of the pumice tells the story of what happened.

    Joseph Knafelc, lead author of the research, said the new model put
    forward in the research challenged the known depth limits for explosive eruptions.



    ==========================================================================
    "The common theory is that underwater eruptions, particularly in deep
    water such as at Havre, cannot be explosive and instead make lava flows
    on the seafloor," Mr Knafelc said.

    "But few submarine eruptions have been able to be observed, and past
    studies had failed to consider the existence of the pink pumice in the
    pumice raft.

    "The colour in this case is critical -- the pink to red colour tells us
    the pumice had to be ejected into the air at temperatures above 700 DEGC
    for tiny iron minerals to then oxidise and cause the reddening.

    "The problem is that it was an underwater eruption that had to push up
    through nearly 1 km of ocean. The only way it can do this is if the
    eruption was very powerful and able to punch through the ocean water
    and produce an eruption column in the air." The research details how
    the core of the eruption was a powerful jet and able to be shielded from
    the surrounding water.



    ==========================================================================
    "The pink pumice and its thermal history tell us that the core of the
    eruption column was untouched by the cooling effects of the ocean water," Professor Bryan said.

    "An explosive eruption column could get hot pumice into the atmosphere
    in as little as a few seconds.

    "This was a very powerful eruption. The problem is that previous studies
    had not recognised or downplayed the explosive potential of submarine
    eruptions even in very deep water and thus the hazards posed by submarine eruptions.

    "As a timely reminder, we recently witnessed in Tonga the power of, and devastation and impact from, explosive submarine eruptions, the effects
    of which could be detected around the world." The research team included Professor Andrew Berry and Dr Guil Mallman from the Australian National University, Professor David Gust and Dr Henrietta Cathey from QUT, Dr
    Eric Ferre', from the University of Louisiana at Lafayette, and Daryl
    Howard from the Australian Synchrotron. QUT researchers are from the QUT
    Earth and Atmospheric School and the Central Analytical Research Facility (CARF).

    ========================================================================== Story Source: Materials provided by
    Queensland_University_of_Technology. Note: Content may be edited for
    style and length.


    ========================================================================== Journal Reference:
    1. Joseph Knafelc, Scott E. Bryan, Michael W. M. Jones, David Gust,
    Guil
    Mallmann, Henrietta E. Cathey, Andrew J. Berry, Eric C. Ferre',
    Daryl L.

    Howard. Havre 2012 pink pumice is evidence of a
    short-lived, deep-sea, magnetite nanolite-driven explosive
    eruption. Communications Earth & Environment, 2022; 3 (1) DOI:
    10.1038/s43247-022-00355-3 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/02/220208105257.htm
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