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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), Mantle plumes, , , , Seamounts (underwater volcanic mountains)., Smoke in the water,   

    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 1:03 pm on August 18, 2017 Permalink | Reply
    Tags: , , Hot spot at Hawaii? Not so fast, Hot spots around the globe can be used to determine how fast tectonic plates move, Mantle plumes, Paleogeography, , Seamounts, The Pacific Plate moves relative to the hot spots at about 100 millimeters per year   

    From Rice: “Hot spot at Hawaii? Not so fast” 

    Rice U bloc

    Rice University

    August 18, 2017
    Mike Williams

    Rice University scientists’ model shows global mantle plumes don’t move as quickly as thought

    Through analysis of volcanic tracks, Rice University geophysicists have concluded that hot spots like those that formed the Hawaiian Islands aren’t moving as fast as recently thought.

    Hot spots are areas where magma pushes up from deep Earth to form volcanoes. New results from geophysicist Richard Gordon and his team confirm that groups of hot spots around the globe can be used to determine how fast tectonic plates move.

    1
    Rice University geophysicists have developed a method that uses the average motion of hot-spot groups by plate to determine that the spots aren’t moving as fast as geologists thought. For example, the Juan Fernandez Chain (outlined by the white rectangle) on the Nazca Plate west of Chile was formed by a hot spot now at the western end of the chain as the Nazca moved east-northeast relative to the hotspot forming the chain that includes Alejandro Selkirk and Robinson Crusoe islands. The white arrow shows the direction of motion of the Nazca Plate relative to the hot spot, and it is nearly indistinguishable from the direction predicted from global plate motions relative to all the hot spots on the planet (green arrow). The similarity in direction indicates that very little motion of the Juan Fernandez hot spot relative to other hot spots is needed to explain its trend. Illustration by Chengzu Wang.

    Gordon, lead author Chengzu Wang and co-author Tuo Zhang developed a method to analyze the relative motion of 56 hot spots grouped by tectonic plates. They concluded that the hot-spot groups move slowly enough to be used as a global reference frame for how plates move relative to the deep mantle. This confirmed the method is useful for viewing not only current plate motion but also plate motion in the geologic past.

    The study appears in Geophysical Research Letters.

    Hot spots offer a window into the depths of Earth, as they mark the tops of mantle plumes that carry hot, buoyant rock from deep Earth to near the surface and produce volcanoes. These mantle plumes were once thought to be straight and stationary, but recent results suggested they can also shift laterally in the convective mantle over geological time.

    The primary evidence of plate movement relative to the deep mantle comes from volcanic activity that forms mountains on land, islands in the ocean or seamounts, mountain-like features on the ocean floor. A volcano forms on a tectonic plate above a mantle plume. As the plate moves, the plume gives birth to a series of volcanoes. One such series is the Hawaiian Islands and the Emperor Seamount Chain; the youngest volcanoes become islands while the older ones submerge. The series stretches for thousands of miles and was formed as the Pacific Plate moved over a mantle plume for 80 million years.

    The Rice researchers compared the observed hot-spot tracks with their calculated global hot-spot trends and determined the motions of hot spots that would account for the differences they saw. Their method demonstrated that most hot-spot groups appear to be fixed and the remainder appear to move slower than expected.

    “Averaging the motions of hot-spot groups for individual plates avoids misfits in data due to noise,” Gordon said. “The results allowed us to say that these hot-spot groups, relative to other hot-spot groups, are moving at about 4 millimeters or less a year.

    “We used a method of analysis that’s new for hot-spot tracks,” he said. “Fortunately, we now have a data set of hot-spot tracks that is large enough for us to apply it.”

    For seven of the 10 plates they analyzed with the new method, average hot-spot motion measured was essentially zero, which countered findings from other studies that spots move as much as 33 millimeters a year. Top speed for the remaining hot-spot groups — those beneath the Eurasia, Nubia and North America plates — was between 4 and 6 millimeters a year but could be as small as 1 millimeter per year. That’s much slower than most plates move relative to the hot spots. For example, the Pacific Plate moves relative to the hot spots at about 100 millimeters per year.

    Gordon said those interested in paleogeography should be able to make use of the model. “If hot spots don’t move much, they can use them to study prehistorical geography. People who are interested in circum-Pacific tectonics, like how western North America was assembled, need to know that history of plate motion.

    “Others who will be interested are geodynamicists,” he said. “The motions of hot spots reflect the behavior of mantle. If the hot spots move slowly, it may indicate that the viscosity of mantle is higher than models that predict fast movement.”

    “Modelers, especially those who study mantle convection, need to have something on the surface of Earth to constrain their models, or to check if their models are correct,” Wang said. “Then they can use their models to predict something. Hot-spot motion is one of the things that can be used to test their models.”

    Gordon is the W.M. Keck Professor of Earth Science. Wang and Zhang are Rice graduate students. The National Science Foundation supported the research.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Rice U campus

    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

     
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