QUESTION:
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I am researching information about the extent of Glacial Lake Missoula.
Some references say that it it did not include Flathead Lake because an
ice dam from the Flathead glacier prevented it. Other references say
that Glacial Lake Missoula covered the Flathead Valley, and extended all
the way into the Kalispell area. Can you help? Thanks.
Charlotte F.
ANSWER:
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Charlotte:
Both are correct. Flathead lobe of Cordilleran icesheet (like all
end-of-Pleistocene glaciers) receded over some time. Flathead lobe did so
while glacial Lakes Missoula lay against its southern margin. There was a
succession of perhaps a hundred such lakes, the lake dumping suddenly once
every few decades as a colossal flood through Washington's Channeled
Scabland. At its maximum stand, the Flathead lobe of Cordilleran
icesheet covered area of Flathead lake, the southern margin of the glacier
forming the big moraine
at Polson. As the glacier margin receded north over next 2,000 years or so, the
succession of lakes Missoula drowned territory farther and farther north. This
margin between ice to the north and glacial Lake Missoula to the south eventually
crept north of Kalispell -- before the lake itself finally ended.
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If you have an interest in basic scientific literature, try this, available
in any university research library:
R. B. Waitt "Case for periodic, colossal
jokulhlaups from Pleistocene glacial Lake Missoula," Geological Society of
America Bulletin, v. 96, p. 1271-1286 (Oct. 1985 issue).
Reference list at
end has citations to numerous earlier works. If you are not into science
literature, it's not as bad as it may sound, this one fairly readable and
with many photos.
Hope this helps, Richard Waitt, January 1999
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