Quote:
Originally Posted by AstralTraveller
The 'V' for river 'U' for glacier is not completely correct. As far as I know glaciers do erode V valleys into U valleys, and straighten them (glaciers don't meander). Half Dome in Yellowstone would be the text book example. However rivers can produce both V and U profiles. The controls are many, varied and debated in the literature.
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Yes, rivers can produce U shaped profiles but that's not usually the case in most instances. By and large, they produce V shaped profiles. The glaciation in Oz was more of a small icecap type of cover rather than mostly individual valley glaciers. The morphology of the Australian Alps and the surrounding areas is indicative of this. Plus you also have to remember that this ice was deposited on top of an already existing erosional surface (a peneplain). Actually, the whole of the GDR, as it is now, is a fairly recent landform...only began to form around 20-25Ma when the eastern margin of the continent underwent epeirogenic downwarping. The peneplain I speak about is easily seen, if you know what you're looking for. Go to the top of Koscuisko and look out over the surrounding peaks and off to the horizon. You'll see they're relatively flat lying and that you can trace out a surface running from peak to peak. That's the old peneplain...it used to be at (or close to) sea level once
Actually, the whole eastern seaboard is one side of a rift valley...the other half is the Lord Howe Rise, New Caledonia (on the Norfolk Rise) and New Zealand. The floor of the valley is the Tasman Sea. It hasn't quite opened up completely as it's nearly joined to Oz at a point just off Rockhampton.
Just as an aside, the Coral Sea is a failed rift, where the tail of PNG began to rift away from Oz (off the Queensland Plateau) around 15Ma but never completely split.