I love geology, and if I weren’t an astronomer, writer, and internationally beloved blogger full time I’d probably take classes in rocks. I’m also fascinated by Antarctica (I came close to applying to go many years ago), so it’s especially cool to hear about both together.
And hey, if I can throw in a smackdown of young-Earth creationists, then that’s sauce for the goose.
Geologists scoping out a glacier in Antarctica found a piece of granite there. Finding rocks on the ice isn’t that unusual; there are flows and currents in the ice that bring up rocks from below, and in fact that’s how meteorites are found so commonly on the frozen continent.
But this granite was unusual. Basically, its structure matched that of granite found in only one other place: North America. Not only that, radioactive dating tests using several methods all match the age of the same granites in North America. So how did that rock get to Antarctica?
Thing is, there is an explanation already in place about this: continental drift. The idea is that eastern Antarctica (along with part of Australia) was once joined to North America, forming a bigger continent called Rodinia. Tectonic action separated the two, with Antarctica drifting south. There is a long streak of this odd granite across America, from California up to Newfoundland. But on the west coast it stops suddenly, right at an ancient rift valley, as if the continent were sheared in two.
See where this is going? The rock found in Antarctica supports the idea that the continent was once way up here, split off, and headed for points south.
Now think on this: we can measure the speed of continental drift very accurately (obAstro: very long baseline interferometry is a technique that links radio telescopes across the planet. The positions of the ‘scopes must be known so accurately that astronomers have to account for tectonic plate drift!), and we know how far away the continents are. Let’s be rough and say that Antarctica is 15,000 km from California, and the drift rate is 3 cm/year. That means it broke away from America about 500 million years ago (remember, a rough estimate). Now, the true age is tougher to find; the continents remerged into Pangia after Antarctica broke off, and the flow rate might change somewhat (the best estimates are that the breakup occurred about 750 million - 1 billion years ago).
But I’m thinking that no matter what, we’re talking ages significantly longer than say, 6000 years. In fact, unless Antarctica was moving at a pace faster than you can jog, we’re talking millions if not hundreds of millions of years here.
Of course, creationists have an answer for this, including “catastrophic plate tectonics”, which apparently can have all the continents scurrying across the face of the Earth like cockroaches avoiding light. Go ahead and read that link; it’s pretty entertaining. According to them, the continents all got pushed around by Noah’s flood, then suddenly stopped, except not really stopped; now they move slowly, and at just the right speed to be in concordance with the hundreds of other pieces of evidence that show that the Earth is billions of years old.
You can’t make this stuff up.
Oh wait. Yes you can, if you abandon reality. But you won’t be right. It’s something like what the great scientist Philip J. Frye said, trying to keep score: “Crazy theories one, regular theories a billion.”
Except, of course, he was off by one.
Tip o’ the trilobite to Jess Zielinski at the USA Today blog. Transantarctic Mountain range image credit: John Goodge/University of Minnesota-Duluth. Details of this find are in Science Magazine, Volume 321, July 11, 2008.