Wenatchee Valley Ice Age Flood
Self Guided Tour Map
Driving through central Washington, one can't
help but notice an extraordinary geological panorama unfolding
along the roadways. What most people fail to realize is that
the entire terrain; hillsides, cliffs, valleys, and canyons created
over millions of years, was dramatically reshaped by an unusual
series of events, which took place during the end of the last
Ice-Age.
Approximately 17,000 years ago near the end
of the Pleistocene Epoch enormous glaciers covered nearly one
third of North America. The western portion of the glacial
ice was known as the Cordilleran Ice Sheet and the eastern
portion as the Laurentide Ice Sheet. East of the Cascade Mountains,
the Okanogan lobe of the Cordilleran Ice extended south on
a line between what is now Chelan and Coulee City.
Farther east a lobe of advancing ice blocked
the Clark Fork River at the point where the river passed through
the Bitterroot Mountains. This buildup of ice blocked the drainage
of a large portion of what is now northwestern Montana. The
subsequent backup of water from the melting glaciers formed
an enormous lake known today as Glacial Lake Missoula. Although
we don't know the eventual height reached by the ice dam, high
water marks on the mountainside indicate a depth of approximately
2000 feet.
Exactly what happened next is still open to
speculation; however, evidence shows the ice dam was eventually
breached. When the dam collapsed it permitted catastrophic
flooding of the landscape to the west. With incredible force,
approximately 500 cubic miles of water and glacial ice burst
through the channel gap, sweeping all before it, as it roared
westward.
This massive flow of water scoured the soil from the landscape,
breaking loose enormous chunks of rock, which it rolled and
tumbled along for miles. Icebergs with incorporated large boulders
or erratics floated on the muddy turbulent flood-waters until
finding a quiet resting place sometimes hundreds of miles from
their ice dam origin.
It is believed the force of the rushing water
was so great a mere four days were required to drain the entire
lake. Today, we can see evidence of how the floods carved out
more than 50 cubic miles of earth, deposited mountains of gravel,
and scattered 200 ton boulders across the landscape. This astounding
process is believed to have happened not once, not twice, but
again and again, possibly as many as 100 or more times.
Additional information about the Ice Age Floods is available at www.iceagefloodsinstitute.org
Contact the WVCVB at 800-572-7753 or Request
a Map here.
Download mp3 Audio Files for Tour Stops
(Short 30 mile loop version)
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