Orogeny by jerks - June 06, 2008
Mountains appear to be pushed up faster than we thought, according to a group of researchers who’ve been looking hard at the Andes.
If the work is right our understanding of mountain formation made need some tweaking (National Geographic, PA, New Scientist, Reuters).
In this week’s Science the team review several recent studies, and conclude that rather than rising slowly over 40 million years, “recent studies of the Andes indicate that their elevation remained relatively stable for long periods (tens of millions of years), separated by rapid (1 to 4 million years) changes of 1.5 kilometers or more”.
This, says author Carmala Garzione of the University of Rochester, supports a controversial theory of orogeny – mountain building - called delamination.
The crunching movement of plates that pushes up mountains generally leaves them with a heavy ‘root’, says Garzoine. Previous thinking holds that this root is gradually eroded by the Earth’s mantle and the mountains gradually rise as a result.
Delamination holds that what actually happens is the root slowly moves downwards until is suddenly breaks off and sinks. Instead of a gradual move up, the mountains do a (relatively) rapid jump. In this case, says Garzoine, the Andes went from under 2km to 4km in less than 4 million years (press release).
As an aside, Garzoine won the 2007 Young Scientist Award at the Geological Society of America, and was presented with it along with this (scansion-challenged) rhyme:
There was a geologist named Garzione
Whose work in Tibet took her far along.
For the altimetry game
Soon gave her great fame
And now she’s entitled to party-on.
Image: Garzione high in the Andes / University of Rochester
