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  • Rights: University of Waikato
    Published 26 September 2018 Referencing Hub media
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    Dr Demian Saffer and Aliki Weststrate from JOIDES Resolution expedition #375 tell us how scientists read the clues found in core samples taken from deep under the ocean.

    Point of interest: Why do you think Aliki compares magnetic reversals to a barcode in the rock?

    Note: This video footage was bounced off a satellite1 during a Skype session with Otumoetai Intermediate School students. If you find the sound quality difficult, please refer to the transcript.

    Transcript

    DR DEMIAN SAFFER

    If we look at the cores, they don’t tell us anything about the time of an earthquake, but what they do tell us about is the time during which they were laid down, so when these sediments2 were approximately deposited. There are a couple of different ways to tell how old they are, and as they are laid down, of course, they are laid down in layers. The oldest ones are on the bottom and then they get younger as you go up. And the two primary ways that we figure out how long that takes or how old the rocks are with fossils or with the magnetic signatures.

    The fossils – we use the word microfossils – and if you look under a microscope3, you see these tiny shells. We know that certain collections of species4 were around in certain time periods in Earth’s history, and that’s really well calibrated or really well known and so you can actually start to map out say the bottom of this core might be 30 million years old and a few metres5 above that it might be 28 million years old, so you not only get the ages but you also figure out then whether there are time periods where things were laid down really rapidly, time built up quickly or time periods where maybe it was more slowly deposited.

    And the other way that we can view this is taking detailed magnetic measurements, and that is again a way of measuring time because we also know that Earth’s magnetic fields flip back and forth over its history and that’s known kind of independently, it’s known pretty well. So mapping those what are known as magnetic reversals down the core is basically like going back in time when you go down the core, so you can figure out the ages of the material based on those flip flops of the magnetic field6 that are preserved in the rock.

    ALIKI WESTSTRATE

    And you can hear that beeping behind us, that’s virtually what Demian is talking about. That’s from the cryomagnetometer, which is measuring the magnetic reversals. It’s like a barcode in the rock.

    Acknowledgements
    Dr Demian Saffer, Pennsylvania State University
    Aliki Weststrate
    International Ocean Discovery Program (IODP)
    Australia and New Zealand International Ocean Discovery Program Consortium (ANZIC)
    GNS Science
    Otumoetai Intermediate School

    Close-up footage of dinoflagellates7 micrographs and microscope from JOIDES Resolution expedition #318 by ZCENE Moving Media for IODP courtesy of Ocean Leadership, IODP and ZCENE

    Three stills of cryomagnetometer courtesy of Nina Rooks Cast, IODP and JOIDES Resolution Science Operator

    All other footage from ship to shore video conference from JOIDES Resolution expedition #375 courtesy of Otumoetai Intermediate School

    1. satellite: Any object that orbits around another object.
    2. sediments: Material that settles to the bottom of a liquid. In geology, it describes the solid fragments of inorganic or organic material that come from the weathering of rock and are carried and deposited by wind, water or ice.
    3. microscope: An instrument that uses a lens or a series of lenses to magnify small objects.
    4. species: (Abbreviation sp. or spp.) A division used in the Linnean system of classification or taxonomy. A group of living organisms that can interbreed to produce viable offspring.
    5. metre: The base unit of length in the International System of Units (SI).
    6. magnetic field: The zone around a magnet in which a magnetic force can be detected.
    7. dinoflagellate: Microscopic single-celled organism that lives in freshwater and seawater. Under warm conditions, marine species can grow and spread to cause a red ‘bloom’ visible in the sea.
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      satellite

    1. + Create new collection
    2. Any object that orbits around another object.

      species

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    4. (Abbreviation sp. or spp.) A division used in the Linnean system of classification or taxonomy. A group of living organisms that can interbreed to produce viable offspring.

      dinoflagellate

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    6. Microscopic single-celled organism that lives in freshwater and seawater. Under warm conditions, marine species can grow and spread to cause a red ‘bloom’ visible in the sea.

      sediments

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    8. Material that settles to the bottom of a liquid. In geology, it describes the solid fragments of inorganic or organic material that come from the weathering of rock and are carried and deposited by wind, water or ice.

      metre

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    10. The base unit of length in the International System of Units (SI).

      microscope

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    12. An instrument that uses a lens or a series of lenses to magnify small objects.

      magnetic field

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    14. The zone around a magnet in which a magnetic force can be detected.