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  • richardmitnick 10:02 am on January 7, 2019 Permalink | Reply
    Tags: Antarctic Circumpolar Current (ACC), , Australia and Antarctica, , Did a hotspot break up your relationship?, , Lithosphere (the Earth’s crust and upper mantle), , , , , Seamounts (underwater volcanic mountains)., Smoke in the water, University of Tasmania   

    From CSIROscope: “Did a hotspot break up your relationship?” 

    CSIRO bloc

    From CSIROscope

    7 January 2019
    Sophie Schmidt

    1
    Women make up 85% of scientists on this voyage of RV Investigator, which is being led by the University of Tasmania.

    RV Investigator Australia

    We’re back out on the waves on board RV Investigator serving up live science plucked fresh from the high seas – and what a voyage it’s been! Since departing Hobart just after Christmas, we’ve been busy sailing for science – not in pursuit of freaky abyssal fish, nor whale watching or shipwrecks – this time we’ve set out for the love of rocks.

    Yep, you read it correctly. The Chief Scientist, Dr Jo Whittaker from the University of Tasmania is leading a team of geologists on a two-week voyage to undertake research into one of those huge, soul-searching kind of break ups. Think less Ariana and Pete (hello, millennials, are you reading CSIROscope?) and more Australia and Antarctica.

    We’re hoping that we might get the closure we need by investigating an area hundreds of kilometres off the coast of Tasmania brimming with seamounts (underwater volcanic mountains).

    All of this drama went down like, 35 million years ago, so we should really be over it by now, but according to Jo, it’s vital that we understand what happened in Antarctica’s past in order to predict its future.

    2
    Jill, CSIRO summer scholar student (right) has been busy mapping seamounts as part of our Geophysical Survey and Mapping (GSM) team.

    Smoke in the water

    Seamounts are caused by mantle plumes – basically, the homewreckers of the lithosphere (the Earth’s crust and upper mantle). Mantle plumes are an up-welling of extra-hot molten rock (magma) from the mantle below and they can seriously mess stuff up. They can cause the Earth’s crust to weaken and rise up through the sea floor, creating big structures such as seamounts and large underwater plateaus, like the Kerguelen Plateau in the Southern Ocean.

    While a mantle plume more or less stays put over time, tectonic plates can continue to drift over it, resulting in seamounts sprouting up in chains across the seafloor. A mantle plume can also cause the Earth’s surface to be uplifted.

    Jo thinks that if we can determine the age and the order in which the seamounts we are studying sprouted as a result of the Balleny mantle plume, we’ll get a better understanding of the role this plume played in this epic break-up.

    “Antarctica underwent a dramatic change 34 million years ago going from Tasmanian rainforests to a glaciated state,” says Jo.

    “Around the same time, it’s thought that the Tasman Gateway, separating Antarctica from Tasmania, opened up.”

    “This research is all about determining whether the mantle plume played a role in opening the Gateway.”

    3
    Voyage Chief Scientist Jo Whittaker inspects the contents of the latest geological treasure haul.

    Rockin’ n rollin’

    Faced with the prospect of a dry ship on New Years’ Eve and oscillating bouts of sea sickness – compounded by my baseline understanding of geology (which has marginally improved), it’s been a seamount-shaped learning curve catching up on the science above and below decks.

    RV Investigator operates 24 hours a day (eye-masks issued on board say “good science doesn’t sleep but good scientists do”) and being on board this world-class research vessel feels like living inside a big, heaving, cooperative sea creature, fuelled by the enthusiasm and smarts of the crew, scientists and support staff on board.

    2
    (In case you can’t tell) Tom, PhD student from University of Tasmania is excited to find some fresh basalt, because it will clue us in to the age of one of the seamounts.

    Much to one geologist’s delight, we occasionally dig up sediment. Popping this under the microscope can reveal a catalogue of million-year-old microfossils including the remnants of coral and plankton which can be dated.

    Everyone is connected on board by some advanced and not so advanced technology. It’s not unusual to wake up to a message from a scientist at 2am posting a photo from another ‘gorgeous dredge’ or to find napkins passionately scribbled with geological diagrams lying around the ship’s galley.

    4
    RV Investigator has advanced multibeam systems that can map to full ocean depth.

    Navigating the unknown is, of course, made much easier with detailed maps and our geospatial mapping team has been constantly collecting seafloor data in rotating 12-hour shifts. The maps are used to decide which part of the seamount we’d like to sample. The ship’s winch is then used to lower a dredge down to thousands of metres below the ocean surface to sample along the top of the seamount.

    Enough about us, though – let’s jump into a quick recap of why we’re here.

    Australia and Antarctica – a lava story
    When things were good, they were really good

    We don’t know how long Tasmania and Antarctica shacked up together before separating around 100 million years ago but their relationship goes back at least 500 million years (New Zealand came along for the ride too #itscomplicated).

    But their issues only became bigger and bigger

    At some point, maybe around 80 million years ago, tension rose to the surface. The Balleny mantle plume, a hotspot, appeared on the scene and fired up seamount after seamount in progressive chains. After being so close for so long, Antarctica and Tasmania started to drift apart.

    They decided their problems were just too big to solve

    At first, Tasmania started to back off slowly, at a rate of a few millimetres or so per year.

    Then, around 35 million years ago, rapid uplift of the crust saw Tasmania start zipping north at around 7 centimetres per year. It was time for Tasmania to move on, and leave the hotspot and Antarctica behind.

    Antarctica turned pretty frosty post-split

    Around 34 million years ago Antarctica became increasingly cold – icy, if you will – and the happy memories of the flora and fauna it once shared with Tasmania became a thing of the past. Perhaps Tasmania still carried a flame as it moved north – after all, its rocks, landforms, soils and vegetation are all by-products from a long-term relationship with Antarctica.

    As continental drift accelerated, the sea floor widened enough to form a gateway (opening) for colder waters to start circulating around Antarctica. We call this the Antarctic Circumpolar Current (ACC), which thermally isolates Antarctica and helps keeps it cold.

    It’s possible that the uplift of the seafloor could have led to the opening of the Tasman Gateway – and the related onset of the ACC. Determining how and when the seamounts formed in this region will help us better understand the evolution of the ACC.

    5
    Emily is an Australian teacher on board under our Educator on Board Program. When she’s not assisting scientists with preparing samples, she’s coming up with new geological slants for the school curriculum.

    Get your rocks off (the dredge and into the lab)

    Even though things have cooled off, we still have some lingering questions to be answered. Did continental drift alone cause the Tasman Gateway to open, leading to Antarctica’s progressively cold state? How drastically did the Balleny mantle plume affect the seafloor over time?

    Out here, Jo’s looking for those answers in the rock samples, which she describes as ‘geological time capsules’– they’ll be dated and analysed back at the lab.

    “All of the data we’re collecting will be used to train better models used to predict what will happen to Antarctica’s future coastline and the melting of its ice sheets.”

    “We’ll understand how the Tasman gateway opened – and whether or not the mantle plume played a major role in the glaciation of Antarctica.”

    6
    Scientists are seeking to join the dots to better understand this chain of seamounts that stretches across the Tasman Sea.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    SKA/ASKAP radio telescope at the Murchison Radio-astronomy Observatory (MRO) in Mid West region of Western Australia

    So what can we expect these new radio projects to discover? We have no idea, but history tells us that they are almost certain to deliver some major surprises.

    Making these new discoveries may not be so simple. Gone are the days when astronomers could just notice something odd as they browse their tables and graphs.

    Nowadays, astronomers are more likely to be distilling their answers from carefully-posed queries to databases containing petabytes of data. Human brains are just not up to the job of making unexpected discoveries in these circumstances, and instead we will need to develop “learning machines” to help us discover the unexpected.

    With the right tools and careful insight, who knows what we might find.

    CSIRO campus

    CSIRO, the Commonwealth Scientific and Industrial Research Organisation, is Australia’s national science agency and one of the largest and most diverse research agencies in the world.

     
  • richardmitnick 10:28 am on January 15, 2018 Permalink | Reply
    Tags: , , University of Tasmania,   

    From COSMOS: “Underwater eruption largest in living memory” 

    Cosmos Magazine bloc

    COSMOS Magazine

    15 January 2018
    Andrew Masterson

    US-Australian team find surprises and complexity at Pacific ocean volcano site.

    1
    A remotely operated vehicle (ROV) lands on the seafloor at Havre submarine volcano to retrieve a heat flow monitor. Woods Hole Oceanographic Institute.

    The first close quarters investigation of what was possibly the largest underwater volcanic eruption in modern history has uncovered a carpet of pumice rocks, some as big as motor vehicles, and unexpected ocean-bed lava flows.

    In a paper published in the journal Science Advances, a research team led by the University of Tasmania in Australia and the Woods Hole Oceanographic Institution (WHOI) in the US report on the use of two autonomous underwater vehicles to explore the aftermath of the eruption of the 2012 Harve volcano, which lies between New Zealand and American Samoa in the southwest Pacific Ocean.

    The volcano blew on July 18, 2012, an event noted only when passengers on an airliner flying above the Kermadec Islands (of which Harve is an underwater component) noticed a huge number of pumice rocks floating on the surface of the ocean. The raft of rocks eventually covered almost 400 square kilometres.

    Three years later, the joint Australian-US expedition headed to the blast site.

    “We knew it was a large-scale eruption, approximately equivalent to the biggest eruption we’ve seen on land in the Twentieth Century,” says Australian volcanologist Rebecca Carey, and co-chief scientist on the expedition.

    Carey and her colleagues suspected they would find evidence of a deep-sea explosive eruption – the commonest form of underwater volcanic activity – but what they discovered was different.

    Instead of the classic blast pattern associated with explosive eruptions, they saw an ocean floor littered with large lumps. So unusual was the find that at first co-author Adam Soule from WHOI thought something had gone wrong with the autonomous vehicles’ imaging system.

    “It turned out that each bump was a giant block of pumice, some of them the size of a van,” he says. “I had never seen anything like it on the seafloor.”

    Having gathered as much evidence as possible, the team concluded that the Harve volcano had undergone an underwater silicic eruption, characterised by the forceful emission of viscous, gas-filled lava.

    This made for an exciting find. Very little is known about silicic eruptions. They are extremely violent acts, but because they take place deep underwater in vast oceans they are very rarely recorded. Most of the current knowledge about their behaviour comes from geologic records rather than observation.

    Already, the team’s findings are adding considerably to the picture. The Harve eruption, they discovered, was a complex affair, with lava emerging from 14 vents, between 900 and 1220 metres below sea level.

    While explosive eruptions produce mainly pumice, this one also produced significant amounts of ash, lava flows and lava domes.

    Although an estimated 75% of the erupted material headed to the sea surface and eventually floated away, that which remained underwater was enough to spread across the ocean floor for several kilometres.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
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