Re: Questions from a YEC Convert

Glenn Morton (
Mon, 01 Dec 1997 05:04:15 -0600

At 10:02 PM 11/30/97 -0800, Arthur V. Chadwick wrote:
>At 09:08 PM 11/30/97 -0600, Glenn wrote:
>>In western
>>Montana, a large basin filled and drained several times to form
>>Lake Missoula. About 18,000 years ago its moraine dam in
>>northern Idaho suddenly broke. A wall of water rushed across
>>eastern Washington with incredible velocity. This catastrophic
>>flood scoured channels and deposited immense gravel bars over a
>>large part of the Columbia Plateau (channeled scablands)."~Robert
>>H. Dott, Jr., and Roger L. Batten, Evolution of the Earth, (St.
>>Louis: McGraw-Hill Book Co., 1971), p. 447
>>A 2,000 foot head of impounded water swept across the Columbia Plateau. The
>>erosion was only able to scoop out basins as deep as 135 feet and left river
>>bars 100 feet high and more. "Current ripples 10 feet and more in height"
>>were scattered over the region. A 200 square mile gravel delta was laid
>>done at the joining of the Willamette and Columbia valleys. But no Grand
>>Canyon was excavated. (See J. H. Bretz, "The Lake Missoula Floods and the
>>Channeled Scabland", Journal of Geolgoy 77:505-543, 1969) and Bretz Jour. of
>>Geol. 23, pp 139-149 and Vol 31, pp 617-649
>According to Sheldon, the deepest scours *in solid basalt* were 900 feet
>deep. That is in solid basalt, not in mud, or shale or limestone. There
>were blocks of granite up to 20 ft diameter transported for 50 miles or
>more, and many blocks of basalt 10 ft diameter, and gravel bars up to 150
>ft deep. There were 50 foot high ripples with a period of 400 feet. And all
>of this stuff was essentilaly not reworked after its catastrophic emplacement.

Even if I grant this, that is hardly a Grand Canyon with 5000 feet of
erosion and it is for a short distance, not the hundreds of miles of length.
Has anyone on your side calculated how much water would be required to
suspend the quantity of sediment needed to excavate the Grand Canyon? Could
that lake you all propose have held that amount of water? It is time for
you all to do a calculation. :-)

>If the Grand Canyon area were deluged with a wall of water 2000 feet high,
>given the relative differences in erodability of the different formations,
>I would think it would be a rather simple task to strip the Tonto Plateau
>of overburden. If the overburden was further in different stages of
>consolidation, as some have suggested, this would only exacerbate the process.

Once again, how much water would be needed to carry that much sediment?


Adam, Apes, and Anthropology: Finding the Soul of Fossil Man


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