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Science

We All Nearly Missed the Largest Underwater Volcano Eruption Ever Recorded (sciencealert.com) 41

schwit1 quotes ScienceAlert: She was flying home from a holiday in Samoa when she saw it through the airplane window: a "peculiar large mass" floating on the ocean, hundreds of kilometres off the north coast of New Zealand. The Kiwi passenger emailed photos of the strange ocean slick to scientists, who realised what it was -- a raft of floating rock spewed from an underwater volcano, produced in the largest eruption of its kind ever recorded.

"We knew it was a large-scale eruption, approximately equivalent to the biggest eruption we've seen on land in the 20th Century," says volcanologist Rebecca Carey from the University of Tasmania, who's co-led the first close-up investigation of the historic 2012 eruption. The incident, produced by a submarine volcano called the Havre Seamount, initially went unnoticed by scientists, but the floating rock platform it generated was harder to miss. Back in 2012, the raft -- composed of pumice rock -- covered some 400 square kilometres (154 square miles) of the south-west Pacific Ocean, but months later satellites recorded it dispersing over an area twice the size of New Zealand itself... for a sense of scale, think roughly 1.5 times larger than the 1980 eruption of Mount St. Helens -- or 10 times the size of the 2010 Eyjafjallajokull eruption in Iceland.

When an underwater robot first sent back detailed maps, one volcanologist remembers that "I thought the vehicle's sonar was acting up... We saw all these bumps on the seafloor... It turned out that each bump was a giant block of pumice, some of them the size of a van."
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We All Nearly Missed the Largest Underwater Volcano Eruption Ever Recorded

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  • If it's recorded, we can just watch it whenever we want. Not sure how we nearly missed something recorded.
  • So is New Zealand going to be the pedicure capital of the world? Smooth as fuck feet when using their beaches?
    • No, but there *is* a large volcanic cauldera (Lake Taupo) in the centre (sic :-) of New Zealand's North Island whose beaches are covered with pumice rocks. If you pick up these rocks and throw them into the lake, they'll float!

  • by Nutria ( 679911 ) on Saturday January 20, 2018 @06:22PM (#55969253)

    You'd think an explosion that size would be noticed all over the Pacific Rim.

  • If it was the Yellowstone Caldera.

  • by Anonymous Coward on Saturday January 20, 2018 @06:36PM (#55969303)

    400 square kilometers is 20x20 square kilometers. That's obviously not an exact number, and "some 400 square kilometer" makes it extra clear. So give a rough number for square miles too. 154 square miles gives an impression of precision that is not justified. Better yet, stop using that archaic unit of distance, but if you're going to keep using it, do it right.

    • Especially that in this context it's unobvious whether they mean nautical miles or land miles, which, unlike the third ("survey") mile differ by a lot. Having three different units by the same name is pure brain damage.

  • How much carbon gets into the atmosphere from the eruption of an underwater volcano? Do events like this help or hurt the climate?
    • Re: (Score:2, Informative)

      by rrohbeck ( 944847 )

      Probably nothing because it was all dissolved in water. Oh and humans emit CO2 at a rate of about 100x of all volcanoes combined.

      • Re:Carbon (Score:4, Informative)

        by Tenebrousedge ( 1226584 ) <.tenebrousedge. .at. .gmail.com.> on Sunday January 21, 2018 @02:30AM (#55970611)

        Quite correct. It's also notable that one of the reasons why AGW was initially considered discredited was that the oceans have an effectively infinite ability to absorb carbon dioxide, many times what humans could possibly liberate. Therefore, it was reasoned, 'carbonic acid' could not build up in the atmosphere. Unfortunately for everyone of Earth, the oceans overturn at a rate far too low to keep up with the amount of excess carbon we're emitting, and consequently we notice this whole 'ppm' thing going up, and as a nice bonus the oceans are acidifying too.

        So as you say, the oceans can deal with the undersea volcanoes just fine. It's the gigatonnes of anthropogenic carbon being dumped directly into the atmosphere that we should probably think about dialing back a few notches.

        (If anyone was looking for a citation for your figure of 100x, they would find it in
        Gerlach, T. (2011). Volcanic versus anthropogenic carbon dioxide. Eos, Transactions American Geophysical Union, 92(24), 201-202. )

        • The CO2 added by volcanoes is negligible, but it's the energy that the volcano adds to the ocean that affects the CO2 concentration in the atmosphere. One kilogram of magma will heat up about 500 kg of water 1 degree Celsius. That adds up to a lot of energy very quickly when talking about a pumice flotilla of 400 km^2.

          • energy that the volcano adds to the ocean that affects the CO2 concentration in the atmosphere.

            CO2 concentrations are not strongly temperature-dependent, no.

            One kilogram of magma will heat up about 500 kg of water 1 degree Celsius. That adds up to a lot of energy very quickly when talking about a pumice flotilla of 400 km^2.

            It is not a lot of energy when compared to the Earth's energy budget, and you're ignoring the heat of vaporization. Why don't you try again, preferably with a reputable citation.

  • by SandorZoo ( 2318398 ) on Saturday January 20, 2018 @07:12PM (#55969419)

    The article couldn't be bothered to actually include any of the photos taken from the plane, but I think you can find one of them here [si.edu].

  • by careysub ( 976506 ) on Saturday January 20, 2018 @08:50PM (#55969841)

    Since the Havre Seamount is at a depth of 900 to 1200 m, while the critical pressure for water is 218 bar (the pressure at 2200 m depth), steam can form in such an eruption so I would have expected a lot of noise from this event. Did no one with hydrophones notice anything?

  • Seems like all the events are July through October 2012. Did any part of this happen recently?
  • by bongey ( 974911 ) on Saturday January 20, 2018 @11:47PM (#55970277)
  • by riverat1 ( 1048260 ) on Sunday January 21, 2018 @02:27AM (#55970599)

    This Wikipedia article on it contains some more information and a couple of satellite photos.

    2012 Kermandec Islands eruption [wikipedia.org]

  • Could this be the major cause of oceans increased acidification(https://en.wikipedia.org/wiki/Ocean_acidification)?
    • Maybe because all the heat of the magma raised the temperature of the ocean water and therefore lowered the pH. The ocean is alkaline because there are stronger bases (sodium, magnesium, calcium) than acids in the water, and that balance controls the carbonate content in the ocean and what is in the atmosphere.

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