Tuesday, November 4, 2008

Potholes Coulee Ellensburg IAFI Field Trip

Click any image to expand

Nick Zentner describes the formation of Potholes Coulee.
On Sunday 2 November 2008 - The Ellensburg Chapter of the Ice Age Floods Institute's President/CWU geologist Nick Zenter (center) led a field trip to Potholes Coulee and the West Bar overlook on Babcock Bench. These are two of the most amazing features along the path of the Ice Age Floods. This was the fourth field trip of 2008 for the Ellensburg Chapter.

Email from Nick:

Ellensburg IAFI enthusiasts -

In a light drizzle, 47 brave folks appeared at CWU's Hebeler Hall parking lot yesterday (Sunday, Nov 2) to carpool to Potholes Coulee near Quincy. Their reward? Sunshine, no wind, and temperatures in the mid-60's at the coulee! Thanks to all that participated. Our next field trip will be in April. Our next lecture will be Wed, December 3 in Hebeler Hall room 121. Details coming soon...


Comment from Tom: Nick- You forgot about the three of us that met up with the group in Grant County (Karl, Bill and Tom) ... so I think the offical count was 50 +2 dogs.


Potholes Coulee -Bruce Bjornstad image

The first stop was on the north rim of the coulee. At that location Nick described the basalt flows and formation of Potholes Coulee. The second stop was out of frame to the north - on Babcock Bench at the West Bar overlook. Yellow line marks trail the group followed to the final lecture location on the coulee floor.


Nick made arrangements with a landowner on the north rim of the coulee for the group's first stop.


Professor Karl Lillquist (CWU Geography and Land Studies Department) displays a 1910 U.S. Geological Survey topographic map of the Quincy Basin.

Karl told the story of J Harlen Bretz being intrigued by what he saw on the map -- huge canyons and cliffs that had once been waterfalls -- at an elevations high above the Columbia River.


Bretz's Flood


In his new book Bretz's Flood - author John Soennichsen describes the 1910 trip 27-year-old J Harlen Bretz made to the Univeristy of Washington's Department of Geology to view the new Quincy Quadrangle map:

"For hours, Bretz poured over the abandoned cataracts, huge pothole depressions, and overhangs of exposed rock he saw in the swirl of lines this map comprised. Although at that time geology was merely an avocation for Bretz, he could clearly see that some unusual event had happened here at some point in the distant past."



Nick describes the Columbia River Basalt Group, Glacial Lake Missoula and the formation of the Channeled Scablands.

Link to USGS Channeled Scablands page.



Walking up to the West Bar overlook on Babcock Bench is always a stunning experience.


Nick couldn't have picked a better spot to describe depositional features created by Ice Age Floods. The giant current ripples and the massive gravel deposit underneath Trinidad are amazing.


This shot of the giant current ripples on West Bar was taken at sunset in June.

The group sure seemed impressed with the ripples on a fall afternoon but I've got to mention that they're much more impressive on a summer evening.
(I've had to walk around rattlesnakes in this area a couple times - Watch where you step if you visit during warmer months).



How big are those ripples over there?

Click on the image to enlarge and check out the guy standing on one of the largest ripples. This image was taken two years ago during a visit to West Bar.


Karl did a great job explaining how the Ice Age Floods took apart the basalt and also described depositional features on the coulee floor.


Nick recaps the day during a rest stop at the west end of the coulee mid-rib.


Thought I'd add this aerial that was taken a few miles south of the area we visited Sunday. This shot gives us a pretty good look at Babcock Bench. If you click the image to enlarge you'll notice West Bar.

3 comments:

Anonymous said...

A day to remember! Thanks for the photos, maps, and general high quality, Tom! Nick Z.

angel said...
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I think it was a really nice experience to go with many people walking and watching incredible landscapes it is great.