Potholes Coulee Traditional Cache

Cache elevation: 1140 ft

General Directions: From SR 281 turn west on White Trail Road. After 3 miles turn left (south) into Quincy Lakes Recreation Area. Go 1.8 miles to trailhead that starts at N47.1384, W119.9309 next to outhouse across from Burke Lake. In winter, access point is from the end of Ancient Lake Road, located northwest of the geocache.

Potholes Coulee

Potholes Coulee is one of the most drammatic features left behind by the great Ice-Age floods. The cache is located at one the best viewpoints where one can really appreciated the awesome scale of the coulee and the floods that created it. J Harlen Bretz, floods pioneer, described Potholes Coulee, or simply The Potholes, as “the best example mapped of a receding waterfall over lava flows known to the writer.” The drainage divide into Potholes Coulee (1200 feet) is the lowest of three coulees that spill into the Columbia Valley from the Quincy Basin. Potholes Coulee, and its neighbors, Crater Coulee and Frenchman Coulee, are spectacular, horseshoe-shaped, tiered cataract canyons that developed when floodwaters rose up to 1425 feet and overflowed several low divides across Evergreen and Babcock ridges. When this happened, an amazing drop of over 850 feet was created over a distance of less than 3 miles between the Quincy Basin and the Columbia River valley to the west! With this difference in water level over such a short distance, floodwaters furiously ate away at the underlying basalt layers, in their vain attempt to establish equilibrium across the divide. All the topsoil was stripped off, along with hundreds of feet of basalt bedrock, along this deep gash between Babcock and Evergreen ridges.

Potholes Coulee consists of two, parallel, amphitheater-shaped, cataract-lined alcoves. The two alcoves are separated by a near-vertical, flood-scoured rib of basalt almost 400 feet high and a mile and half long running down the middle. The upper ends of these alcoves form the Ancient Lake Basin on the north, and Dusty Lake Basin on the south. An upper cataract steps up from these alcoves, forming a wild maze of butte-and-basin scabland all the way up to Quincy Lakes. Deep plunge pools lie at the bases of some cataracts. Beyond the cataracts are found bars of coarse-grained flood deposits, which blanket the bottom of both alcoves westward to Babcock Bench. Elongated depressions (fosses) developed between flood bars and the coulee walls.

Three sets of recessional cataracts are preserved in 2-mile-wide Potholes Coulee. The upper cataract developed across the Roza Member of Columbia River basalt and in places receded as much as 3 miles all the way to Quincy Lakes. Huge columns are characteristic of this basalt member. Another cataract developed across the Frenchman Springs Member, the next oldest basalt member. In some places, these two cataracts are stacked on top of each other, forming a single cataract up to 400 feet tall! This stacking is visible immediately above Dusty and Ancient lakes and where the basalt rib separates the north and south alcoves. A third cataract stepped down into the next oldest basalt member (Sentinel Bluffs) near the mouth of Potholes Coulee along the top of Babcock Bench. The lower cataract appears to have begun to retreat up the coulee when the last scabland floods occurred and prematurely cut off its development.

To experience more incredible features left behind by the Ice-Age floods try finding these other geocaches placed by geologist Bruce Bjornstad:

Staircase Rapids
Upper Goose Lake
Frenchman Coulee Rib
Rattlesnake Slope Erratics
Devils Canyon
Saddle Mountains Overlook (Earthcache)
Wallula Gap Overlook
West Bar Overlook
Lake Sacajawea Flood Bar