Re: Questions from a YEC Convert
Arthur V. Chadwick (firstname.lastname@example.org)
Sun, 30 Nov 1997 22:02:40 -0800
At 09:08 PM 11/30/97 -0600, Glenn wrote:
>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.
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.