[meteorite-list] Large Ice Age Floods Moved 16-Ton Willamette Meteorite To Oregon

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:28:23 2004
Message-ID: <200310081714.KAA21543_at_zagami.jpl.nasa.gov>

http://www.missoulian.com/articles/2003/10/07/news/local/znews03.txt

Floods' footsteps
By JOSEPH B. FRAZIER
Associated Press
October 7, 2003

Institute looks to mark route of Glacial Lake Missoula's overflow

THE DALLES, Ore. - Picture an ice dam 30 miles wide forming a lake 2,000
feet deep and 200 miles long, a lake stretching from the Idaho panhandle
into western Montana and containing more water than Lake Erie and Lake
Ontario combined.

Now picture that dam giving way, and most of its 520 cubic miles of water
thundering out in about 48 hours through four states as it roared across
eastern Washington and west through the Columbia Gorge to the Pacific.

The water would have filled a lake a mile deep and a mile wide from the
Columbia River to San Francisco.

The Missoula Floods, at the end of the last Ice Age about 14,000 years ago,
were the biggest scientifically documented floods ever.

How big were the floods?

Geologists from the U.S. Geological Survey have estimated the flow near the
dam breach of Glacial Lake Missoula at 10 times more than the combined flow
of all the rivers in the world.

The floods spilled over the Columbia River Gorge, and USGS geologist Jim
O'Connor says they probably swelled to 4,000 times the flow of the river
today.

By any account, the Old Testament flood was a leaky faucet by comparison.
And the Missoula Floods occurred repeatedly over the course of about 2,500
years, as new glacial ice dams plugged the river outlet, Glacial Lake
Missoula refilled with water, and the dam then ruptured once again.

Signs and interpretive centers in the Pacific Northwest mark the route of
Lewis and Clark and of the pioneers who followed the Oregon Trail.

But there is nothing similar to mark the Ice Age floods, which were partly
responsible for the appearance of the region's terrain and formed much of
the Columbia Basin.

There are hit-and-miss markers that refer to the flood, O'Connor said, but
they were placed by a variety of organizations and don't tell a
comprehensive, chronological tale of what happened.

A study for the National Park Service, and a growing number of amateur and
professional geologists fascinated by the floods, think that's a shame.

The Park Service study, issued in 2001, suggests an Ice Age Floods National
Geographic Trail that would follow the 600-mile path of the flood, mostly
along existing highways, with signs and information highlighting significant
flood features.

The funding for the study came from Congress, but Congress has not followed
up on its recommendations, which include recognizing the path of floods and
the 16,000 square miles they covered as a nationally significant resource.

The report summary says features of the flood and its pathway make it
suitable for inclusion in the national park system, not as a traditional
park or monument but as an interpretive flood pathway across the four
states.

It recommends that private land not be taken over for the project.

It envisions towns near key flood features as "gateway communities" with
hiking and horse trails, canoeing and kayaking routes that will help
visitors realize the scope of what happened.

"No bill has been introduced yet," said Dale Middleton of Seattle, president
of the nonprofit Ice Age Flood Institute dedicated to educating people on
what the floods were and why they mattered.

"We are trying to get someone in the Northwest congressional delegation to
do so. We have had some contacts," he said.

The institute will meet in The Dalles on Oct. 11 to go over plans for a
geologic interpretive trail.

Middleton said the institute envisions information and visitors centers at
key points along the flood routes.

None of it has gone anywhere, although the effects and traces of the floods
remain very much in evidence.

The floods hit the Columbia River near present-day Wenatchee, Wash., and
roared west. The Columbia Gorge, 80 miles long and up to 4,000 feet deep,
couldn't contain the water, which scoured the rock walls clean and spilled
over, probably widening the gorge.

Geologists compare the gorge to a nozzle that sent the floods roaring out in
a wall of water perhaps 500 feet high at 80 mph, or more, putting Oregon's
Willamette Valley as far south as the Eugene area and present-day Portland
under 400 feet of water.

"Most of Portland is a big sand and debris bar deposited where the flood
slowed down as it spread out over the Portland Basin," said O'Connor, who is
with the USGS Portland office and has researched the floods extensively.

Much of the deep soil that makes the Willamette Valley one of the richer
agricultural areas in the country is from deposits of flood silt.

"The Oregon Trail might have gone somewhere else if the floods hadn't filled
the valley full of sand and silt," he said. It was the Willamette Valley's
fertile soil that attracted many a traveler who set out on the Oregon Trail.
Rich silt left by the flood reaches 100 feet deep in places.

University of Montana geology professor David Alt, who has studied the
floods since the 1960s, wrote in his book "Glacial Lake Missoula and its
Humongous Floods" that his research shows that Glacial Lake Missoula, which
bottled up the Clark Fork River, broke through ice dams and refilled at
least 36 times, probably on average about once every 50 years, and that the
largest floods were the earlier ones.

Some geologists put the number of floods at 50 or higher.

In all, the floods washed out about 50 cubic miles of earth.

O'Conner said it is not clear whether the floods hit inhabited regions.

Residents of Portland's comfortable Alameda Ridge and even posher nearby
Lake Oswego still curse and swear as they tussle with large boulders on
their property, unaware that they may have ridden the floods for 500 miles
encased in icebergs.

The Willamette Meteorite, at nearly 16 tons the largest ever found in the
United States and the sixth-largest in the world, apparently also rode the
flow. It was identified near West Linn south of Portland in 1902 and resides
at the American Museum of Natural History in New York City.

Flood deposits 50 feet thick in the Beaverton area west of Portland are
considered a factor in the area's vulnerability to earthquakes.

In what is now eastern Washington, water flooded today's Spokane Valley to a
depth of about 500 feet. The floods ripped away bedrock and formed deep
canyons, or "coulees," which remain. Erosion and washed-out channels are
visible from space. Some scientists say they curiously resemble those on
Mars.

Scientists have always disagreed over some aspects of the flood, its size
and scope, its frequency.

Some have been pilloried for what they thought, none more than J Harlen
Bretz, a geologist who spent most of his career at the University of Chicago
and did extensive field work in the flood area.

In 1923 he came up with the theory of a catastrophic flood that deluged the
landscape over a matter of days.

Alt notes that this was crosswise with scientific thought that prevailed at
the time - that geologic events took place gradually, not all at once.

Bretz's colleagues thought he was a dunce and a heretic and said so, but
gradually saw it his way as they looked at the evidence he had compiled.

Bretz died vindicated in 1981, well into his 90s.
Received on Wed 08 Oct 2003 01:14:55 PM PDT