How Gondwanaland got Australia to move out of the neighbourhood without being obvious

[sff_corgi_lj]

Gacked from electroweak, co-creator of A Miracle of Science:

From Space.com, BBC Science/Nature News, the Sydney Morning Herald and The Age

Big news from the American Geophysical Union Joint Assembly held in Baltimore this past May 23-26: A team of Ohio University, NASA, Russian and Korean scientists led by Prof. Ralph von Frese from OSU, who had been looking at differences in density that show up in gravity measurements taken with NASA's GRACE satellites noticed, beneath Antarctica's icy surface, a 321-kilometre-wide plug of mantle material — a mass concentration, or "mascon" in geological parlance — that had risen up into the Earth's crust. Cross-referencing against radar imagery, the team found a corresponding 500-kilometre-diameter circular ridge, also still buried beneath 1.6km of ice, which seemed to confirm their suspicions.

The mascon is located in Wilkes Land, East Antarctica; its coast faces Australia, which claims the area as far as the Antarctic Treaty allows such claims.

'...[the impact] could have begun the break-up of Gondwana supercontinent by creating the tectonic rift that pushed Australia northward," the team's leader Ralph von Frese said in a statement. "The rift cuts directly through the crater, so the impact may have helped the rift to form."

The size of the meteor itself has been compared to the city of Sydney; the resulting impact ridge to the size of Tasmania.

The impact is now thought to have started the Permian-Triassic extinction, which wiped out most life on land and in the oceans. Immediate effects would have included shock waves, firestorms, earthquakes, tsunami and vapourised materials contaminating the atmosphere. Secondary side effects from the damage, which punched completely through the earth's crust, would have been supervolcanism perpetuating the environmental changes for centuries.

False-colour radar image of the mascon, ridge and comparison to the Chicxulub crater of Yucatan
Interactive Flash animation of the breakup of Pangaea/Gondwanaland
GIF animation of breakup of Pangaea/Gondwanaland (wow, lookit India fly!)

Any errors in summation are mine, due to the fact that I'm still getting dressed, ack!

Comments

[sff-corgi.livejournal.com]

I have to have a geology 101 TA moment...

Just one?!? ;)

Problem w/ this crater appears to be the 1.6Km of hard ice. Now, if Bush keeps going the way he's going, all they'll have to do realsoonnow is just sweep some slush off.... [/rimshot]

Pangea was the supercontinent that broke up - Gondwanaland was just a piece that broke off...

:nodnod: But it was the Gondwanaland part of Pangea. Hey, what caused India to go scooting around that fast? Or is it just because it's relatively smaller than the other bits and got to be all by itself in the middle of nowhere for so long?

[panamdea.livejournal.com]

Just noticed I'd not replied to this....

It's a good question, and honestly (and possibly embarassingly), I actually don't know. I've had a look at my notes and things and I don't think it's something I've ever covered. It's one of those really obvious questions I've never thought to ask.

I would hazard a guess that there's something about the geometry of the plate boundaries around it which has caused the plate movement to be so rapid. However, what that is, I don't know, as if you look at a map of plate boundaries there's nothing obviously special about the Australian-Indian plate in that respect.

This is going to annoy me for a while and I'm going to have to go and find out....!

I actually heard the guy who presented the data talking about this on science Friday the other week and I wasn't really satisfied by what he had to say either. Though he did say they had planst to do a low level fly over to do more accurate gravity anomaly readings and might look at the "rubble" that glaciers from the area drop to see if it contains any non-terrestrial material. Other than that I've not been able to find much info. My adviser says I can borrow is copy of the PT book that's been recently published, but of course, it doesn't cover this.

[sff-corgi.livejournal.com]

Now, there's always the possibility it's just a PoV thing - it looks, in the animation, relatively fast because of the space around it and the other plates moving away from it simultaneously. They deal with this in deep space astronomy all the time, eh.

But I'd love to know what you find out. I started digging plate tectonics not long after my dinosaur phase, but I think it might be as much for the same reason that I pour over Professor Tolkein's maps, matching up features, as any left-brain reason. ^_^

[panamdea.livejournal.com]

No, it really did move that fast - it's insanley rapid actually. Since the collision with Asia (~50Mya in the Eocene, I believe), India is moving north about 5cm/yr, but before the collision, it was moving about 15cm/yr. That's way faster than any other tectonic plate has ever moved.

I love maps so very much. There's something totally cool about seeing the world spread out in front of you! Palaeomaps are even more fun. There's something fabulous about watching the world change. The father of one of the professor's in my department was a mover and a shaker in the plate tectonics revolution - it's weird to think that such a huge shift in our world view is so recent, relatively speaking.

Every kid goes through a dinosaur phase and a playing in the dirt phase. Some of us just don't grow out of those phases. They call us palaeontologists... ;)