Originally posted by Mentat
How plastic is the Earth? I don't mean like literal plastic, but I mean "how moldable is it?". How long would it take water to erode away ground? Does the amount of water make a difference?
Obviously I'm lost, as far as geology goes, so any help is appreciated 
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sorry to point out anything obvious...
The "ground" is made of many different materials...there are rocks and soils of many different types. Otherwise, geology would not be much of a subject to study would it? Physical geology has all kinds of factors to consider...faulting, fracturing, folding, and probably some other f words. (No, not
that one.) Some rocks are tough for water to erode, other types are easier. "Dirt" can be sand, rock, gravel, silt, clay, till, etc. each of which has different characteristics to consider (not to mention packing, porosity, and other p words...no, not
that one...please get your mind out of the gutter).
In short, there is no short answer. But what the heck, here's a short answer. I seem to recall Sagan saying in his book Pale Blue Dot that it takes something like 10 million years to erode a mountain...or did he say 100 million? Aw, crud. I forget.
In human terms (say, a lifetime) the Earth is, overall, very resilient. Mountains don't seem to change and river banks don't alter that much. Sherpas don't notice that India is smashing into Asia and driving up the Himalyas. Well, perhaps things look static until you see your first mudslide or volcano, then you may wonder what the heck is holding everything together the rest of the time! The mudslide bit is probably a good visual answer to your "amount of water" question.
But in geologic time frames, the Earth is very "plastic". Things are constantly shifting around. Rock flows and crumbles. Dirt is pushed around. New rock forms. Continents drift (what is it, I forget...like an inch per year?) and collide and dive back into the Earth's mantle or are thrust upwards into new mountain ranges.
I'd have to sneak a peak at a geology textbook for specific plasticities/strengths of specific rocks.
