WALLULA GAP: Bottleneck of the Ice Age Floods

When you first hear about how 15,000 years ago, glacial Lake Missoula broke free of its ice dam and raced across the Mid-Columbia Basin – some 500 cubic miles of water traveling at speeds of up to 80 miles an hour – you’re tempted to say bullshit.

That’s what most scientists thought when J. Harlen Bretz first proposed his theory of a great “Spokane Flood” in the early 1920s. But 30 years later, after he and others collected more evidence, and after the advent of aerial photography made it possible to recognize giant “current ripples” in suspect landscapes, scientific opinion began its necessary shift.

On a recent trip to the tri-cities, I spent time in the Horse Heaven Hills, south of Kennewick in order to see some of the evidence for ancient cataclysmic floods as laid out in Bruce Bjornstad’s guidebook, On the Trail of the Ice Age Floods.

Evidently, the Horse Heaven Hills form the defining southern rim of the Mid Columbia ‘Basin’ and when the floods came, the only way through this barrier was the relatively tiny, two mile wide, Wallula Gap.

Driving up the Columbia Gorge in early April was almost a metaphorical journey from darkness to light. Portland lay under its omnipresent gray overcast sky, an ambiguous ceiling that extended almost all the way to The Dalles. But eventually my weary truck broke out into the open, under painfully bright, blue skies where freshly weaned clouds floated peacefully in vast herds, grazing on invisible water vapor.

Pivot irrigation lends credence to the idea that spring has decided to hang out in Kennewick this year.

An idea that is easily dispelled around the next corner

I keep trying to decide if these are pretty or not…and I’m leaning towards pretty.

The trailhead to the Wallula Gap overlook lies on private property. The owners are very accommodating to hunters and hikers and have posted friendly signs that say (provided the bullet spray is light), “Hey, come on in and hunt if you want…just don’t stay overnight.” 

It’s just an extraordinarily bad place to wear an antler hat.

With no clear sense of direction and no compass, my first attempt to find the overlook trail failed.

…and those innocent clouds that had been feeding all day had been transmogrified into something somewhat more threatening.

A mini deluge ensued as the moon fought to ascend over the gap.

Moonrise over Wallula Gap

These long straight valleys are thought to be the result of floods that, “etched out the weaker basalt along one of many tectonic fractures that run through this area.”

On track and steadily gaining elevation (the city of Pasco receding in the distance).

Approaching the overlook.

Bjornstad writes that this cliff would still have been 80 feet under water at the height of one of the Ice Age Flood events.

The distinctive double pillars (Twin Sisters) and the surrounding tortured landscape are thought to be the result of backed up flood waters (from temporary Lake Lewis) squirting through the only available pathway to the sea.

This erratic granite boulder sits atop a plateau of black basalt that comprises the Wallula Gap.

An improbable journey.  A stowaway from a Montana Iceberg.

Muddy water from the Snake River mixes with the Columbia.

Temporary Lake Lewis would have buried the Tri-cities under 800-900 feet of water for almost a week before it would have drained out via the Wallula Gap. The arrival of Homo sapiens on the North American Continent is thought to have been made possible by a land bridge in the vicinity of Russia and Alaska. The land bridge appeared as more and more water got tied up in the continental glaciers of the Ice Age and sea levels receded. Evidence suggests this human migration happened 25,000 years ago – maybe 50,000.

It makes me wonder if there were witnesses to these floods – if early settlers – perhaps whole cultures - were swept away before they learned to read the stories recorded in this area's geology.

Notes:
See also Washington Road Trip - Only two CDs: http://thenarrativeimage.blogspot.com/2009/08/washington-roadtrip-only-two-cds.html for pictures of more Ice Age Flood artifacts including, Palouse Falls and way at the end, Frenchman Coulee, Agatha Tower, and The Fingers 

Most of the data regarding the Ice Age Floods is from Bruce Bjornstad's book, On the Trail of the Ice Age Floods: http://www.keokeebooks.com/IceAgeFloods.html

An excellent source for information regarding Ice Age Floods is Huge Floods.com: http://hugefloods.com/LakeLewis.html  I've linked to the page that describes Lake Lewis, but don't stop there. Huge Floods.com also features the paintings of Stev H. Ominski who tries to imagine what the Floods looked like.

Here is a link to the Ice Age Floods Institute. http://www.iafi.org/

For an impressive visualization of an Ice Age flood at Washington's Dry Falls, see: https://www.youtube.com/watch?v=OqUyAFZFyVo