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Antarctica Once Abutted Death Valley

Posted by kdawson on from the may-i-borrow-some-grey-poupon dept.

Science News has a story of strange bedfellows. It seems that Antarctica was once adjacent to what is now the American Southwest, some 800 million years ago. Earth's continents then formed a supercontinent called Rodinia, predating Pangaea by some 550 million years. "...the ratios of neodymium isotopes in the ancient sediments in the Transantarctic Mountains are the same as those in what was then Laurentia, says Goodge. Also, the hafnium isotope ratios in the 1.44-billion-year-old zircons found in East Antarctica match those of the zircons found in the distinctive granites now found primarily in North America. Finally, the researchers note, the ratios of various isotopes and elements in a basketball-sized chunk of granite found in East Antarctica — a chunk ripped by a glacier from bedrock now smothered by thick ice, the team speculates — match those of granite found only in what was southwestern Laurentia, which today is the American Southwest."

9 of 182 comments (clear)

  1. but wait... by Jafafa+Hots · · Score: 5, Funny

    ... how do we know it was called Rodinia? Who left records?

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    1. Re:but wait... by Max+Littlemore · · Score: 5, Insightful

      Good point. My understanding about the theoretical pre-history of continents only went as far back as Gondwana, which dates back roughly 500 million years and is a very different map to the one in TFA, so I had a look at this to refresh my memory and try to resolve conflicts. If TFA is true, then the continents really do shift pretty quickly and change direction a fair bit too, considering Australia started in the northern hemisphere according to TFA, went South to join Gondwana and is now heading North again.

      But back to your point about how they knew what it was called, I have a related question. How do they know that Eastern Laurentia had crinkle cut coastlines like Canada? Weren't they formed by glacial activity? How does that happen at the equator?

      Also, it wasn't clear to me from TFA whether the magnetic field lines conflict with this theory or support it. If they do conflict, how do we know that the distribution of isotopes isn't due to some other phenomenon?

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    2. Re:but wait... by syntaxglitch · · Score: 5, Insightful

      But back to your point about how they knew what it was called, I have a related question. How do they know that Eastern Laurentia had crinkle cut coastlines like Canada? Weren't they formed by glacial activity? How does that happen at the equator?

      Most likely, they don't know that, or even think that it did. Continental drift maps are usually drawn by moving around the outlines of the modern continents for the most part, probably because that best communicates which parts went where, rather than amorphous blobs labeled things like "p.s. this is actually Canada".

      My understanding would be that the actual outline of the old continents looked nothing like that and we have no way to figure out what they actually did look like.

    3. Re:but wait... by srmalloy · · Score: 5, Interesting

      I happened to catch part of a program on the History Channel this morning that was talking about Rodinia and how the coalition of the continents into a supercontinent disrupted ocean currents, allowing the poles to become colder, expanding the continuously-frozen area until the process ran away, completely covering the Earth in ice until the eruptions that accompanied the breakup of the supercontinent threw CO2 and methane into the air that couldn't be absorbed into the oceans (covered as they were by ice), building up to the point where the greenhouse effect melted a permanent ice-free zone, which (being darker than the ice) would absorb more heat, triggering a positive feedback. The program described this happening in a single freeze-and-thaw, although some 'snowball earth' theories suggest that there were several freezovers as the CO2/methane levels rose and fell until the Cambrian Explosion. It seemed to me, though, that the arguments for Rodinia and Snowball Earth can also be explained by other theories, and that drawing conclusions about conditions that far in the past based on evidence that can accumulate in different ways is going to remain somewhat speculative.

  2. Re:Death Valley is a bitchin place by gardyloo · · Score: 5, Funny

    Fine. One of the reasons there's nobody there is because of all of the assholes on their Harleys :)

  3. Re:Death Valley is a bitchin place by mrbluze · · Score: 5, Funny

    One of the reasons there's nobody there is because of all of the assholes on their Harleys :)

    Taken literally or figuratively, the visuals are not appealing.

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  4. Re:Death Valley is a bitchin place by gardyloo · · Score: 5, Insightful

    True, and I know lots of Harley riders, most of whom are very nice. However, anyone who rides an unmuffled motorcycle and is proud of its noise is, by definition, at least an inconsiderate jerk.

  5. Re:How many supercontinents were there? by Anonymous Coward · · Score: 5, Informative

    The oldest one proposed is called Columbia, existing from 1.8 - 1.5 bya.
    The next widely accepted was Rodinia, existing from 1.3 bya - 800 mya
    The next possible was Pannotia, but it didn't last long, only from 600 - 550 mya.
    The last one was Pangaea, from 250 mya to 150 mya.

    The earliest ones are deduced mainly from paleomagnetism, so there may have been earlier supercontinents that we do not know about due to a lack of rocks that old.

  6. Re:Death Valley is a bitchin place by Anonymous Coward · · Score: 5, Insightful
    Revving your goddamn engine at a stop sign to make your dick sound bigger (0 mph) is, I concede, a safe speed for neighborhood driving. It still wakes up my kid, and any driver who can't see a stationary douchebag on a motorcycle isn't going to take noise into consideration.

    Besides, if being noticed is a problem, why is the standard-issue biker uniform an oh-so-visible black?