Comments Posted By schaffman
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RELIGION AND POLITICS: INTOLERANCE IS GROWING
As an aside, I think the quoted "age" of the Grand Canyon as 550 million years is misleading. Readers should be aware of this when debating the larger issues discussed in Rick's excellent post and the ensuing discussion.
By age, do we mean the canyon's present appearance, when it started to form, or the age of the oldest rocks exposed at the bottom?
The answer to the first is that it's current appearance is fully modern..it's as old as yesterday.
The canyon began to form with the uplift of the Colorado Plateau and subsequent incision of the Colorado River. This started some tens of millions of years ago. (I could look it up but am feeling lazy.)
The oldest rocks in the canyon are Precambian and far older than 550 million years. I'm guessing that the 550 million years figure is from the date of the beginning of the Cambrian Period, represented at the base of the Tapeats Sandstone (the bottom rock formation of the outer canyon).
Anyway, sorry for the somewhat pedantic diversion, but I think it's important to have an understanding of the minutia, here.
Comment Posted By schaffman On 6.01.2007 @ 13:32
