Glacial Lake, Sandpoint Idaho
by Bob Gunter
The pale sun rolled back the mist like a
scroll and the surface of the monstrous lake slowly became
visible in the morning light. The swirling water and ice
covered much of the land except for some of the higher
mountains. Around the lake there was sparse vegetation
growing among the windblown sand dunes through which
greenish-gray rivers cut. Giant cliffs and walls of ice
could be seen far on the northern horizon.
The lake was growing at all times and covered an area the
size of Lake Erie and Lake Ontario combined. Lake Missoula
stretched for hundreds of miles across western Montana. An
ice dam standing about 3,000 feet high was the plug, which
held the huge volume of glacial water in place. The dam was
located where the Clark Fork River meets Lake Pend Oreille
in North Idaho.
Indian Point on Lake Pend Oreille, Sandpoint Idaho
Click photo to enlarge
Nothing, on the surface, gave any
indication as to what was going to transpire at the lake
over 12,000 years ago, but at the base a small stream of
water flowed from the ice. The stream grew until more and
more water came gushing out and the stream grew larger. With
a thunderous roar of breaking ice and rushing water the ice
dam collapsed and in less than 48 hours Lake Missoula was
drained. The force of the 2,000-foot wall of water shooting
out of Clark Fork Canyon measured 10 times the combined flow
of all the known rivers of the world. The ground shook as
between 500 and 600 cubic miles of glacial water roared
through Cabinet Gorge on its way to the Pacific Ocean. The
torrents of water raced forward at the speed of 70 miles per
hour stripping away soil, moving large boulders, and
creating deep canyons, or coulees, in the bedrock. The paths
of the great flood converged in the Pasco Basin. There the
rush of water was slowed by a narrow passage called the
Wallula Gap. This narrow gap caused the waters to back up
and a 1,200-foot lake was formed.
The cause of the largest, scientifically
proven, flood known to man was due to the rapid drainage of
Glacial Lake Missoula. During the ice age a great lobe of
the Cordilleran ice sheet in Canada had moved down the
Purcell Trench into Lake Pend Oreille basin. This resulted
in the Clark Fork valley acting as a dam and creating a
glacial lake, which covered about 3,000 square miles in
western Montana. The breaking of this dam resulted in the
flood leaving its mark across Montana, Idaho, Washington and
Oregon. As the floodwaters engulfed the rivers in an area it
would push back up the major rivers. Lewiston was covered
with water when it pushed back up the Snake River. Wenatchee
and the area around Yakima were covered by water. Coeur
d'Alene, Idaho, Spokane,WA and Portland, Oregon were
inundated by the raging floodwaters.
There is evidence that the great floods
of the Northwest occurred many times and played a big role
in shaping the great Northwest. The scabland of Eastern
Washington, the Columbia basin with its stark cliffs and
waterfalls, the numerous gravel deposits and the huge
potholes found in the path of the flood give a picture of
its force and magnitude. The landscape of Rathdrum, Idaho,
Coeur d'Alene and Spokane, as well as, the Spokane aquifer
are results of the glacial floods.
The scientific data that confirms the
fact that this part of the Northwest was partly formed by a
cataclysmic flood comes from Professor J. Harlen Bretz. He
was a professor at the University of Chicago and in 1923
began a series of papers explaining the origin of the
Channeled Scabland in Washington State. His view that large
scale flooding had caused the dry channels and coulees so
evident in Washington was rejected by the geologists of his
day. Over time, with help from further scientific evidence,
the ideas promoted by Bretz have been accepted.
All photographs have been used with permission of the Bonner County Museum.
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