Bretz Hole

Bretz Hole

Frenchman Coulee at Vantage is home to some of the finest basalt column rock climbing in the world. But what most of you don’t know is that it is also home to the third-deepest natural pit in Washington. By natural pit I don’t mean a pit made by man, such as a strip-mining pit, but a pit made by Mother Nature that has no surface outflow (i.e., the rim is higher than the bottom and the rim extends all the way around the pit).

Natural pits such as these are easy to spot on a topo map. Their contours contain tiny “spikes” pointing in toward the center of the hole. If you count up the number of concentric spiked contours, you can make a reasonable guess as to the depth of the hole.

Here is a list of the deepest natural pits in each state. Note that this list can and is updated as new holes are found.

The pit at Frenchman Coulee has no official name. John Roper has suggested Bretz Waterfall Plunge Hole. I like this name, though I personally would shorten it to Bretz Hole, firstly because his name implies there is an active falls there by the name “Bretz Falls” and secondly because his name is a mouthful…of floodwater.

It was geologist J. Harlen Bretz in the 1920s who first claimed that the Channeled Scablands of Eastern Washington were formed from massive floods coming from bygone Lake Missoula of the last ice age. This lake repeatedly formed when advancing ice would block its outlet. Water would fill the great basins of western Montana to as much as 500 cubic miles of volume. When the ice dam would break the water would flow out in a mighty rush. Thus were born the channels of the scablands.

Now we all know what happens when water goes off a precipice. The water plunges to the base of the precipice. If the terrain/bedrock at the falls are of a relatively weak material, such as basalt, the force of the water can do two things:
1) it can wear away at the lip of the precipice thus eroding it in an upstream direction
2) it can excavate a hole at the base of the falls by a ram scooping effect.

The first of these created/creates the geography of many famous canyons and waterfalls in the world (examples: Niagara Falls and The Grand Canyon of the Gunnison). The second of these has created Bretz Hole. Actually, the first of these has also created Frenchman Coulee. Another example is Dry Falls 40 miles to the NNE of Frenchman Coulee.

As to our Bretz Hole, a voluminous branch of Lake Missoula floodwater repeatedly (approximately 40 times over a 2000-year period) coursed across the expansive flat of present day Moses Lake and George between the Beezley Hills to the north and Frenchman Hills to the south. The floodwaters would plunge off the high ramparts of the Columbia River. The precipice of the falls receded more and more with each new flood and its present-day position is about 1.3 miles from the banks of the Columbia.

I imagine a hole has existed at the base of the falls at every moment in time once the floods commenced. And so as the precipice has receded so has its associated hole.

So how deep is Bretz Hole? Well that’s not an easy question to answer. The contours are hard to decipher in the bottom of the hole. But two independent altimeter measurements (mine and Roper’s) put the depth at 175-185 feet. The lowest point on the rim is about here (est. 860 ft). The lowest point in the hole would then be about 680 ft. Note that this isn’t much higher than the present-day normal pool of 570 ft for the nearby Columbia River where it is dammed by Wanapum Dam to create Wanapum Lake.

Though this pit looks like the maw of a dragon on the topo map, know that it is a trivial descent in terms of terrain difficulties. The crux of your adventure to visit it will be avoiding any fanged serpents that might happen to bar your way and rattle your nerve.

Michelle and I took off from the white gate here and ambled a rock-imbedded old road toward the objective (a bike might be handy here but the imbedded rocks would surely make for an unpleasant ride, not to mention the danger of doing a header into a rattler). The distance from the gate to the bottom of the hole is only a mile and it only takes 20 minutes on foot.



Eventually the old road disappears leaving a sandy descent to the hole’s lower rim. A few hundred yards of cross country gets you there. The final descent is a bit steeper but nothing difficult. Michelle and I thought that the lowest point in the pit was at the far right (SE) corner where talus reaches the bottom. Here we found a softballs-sized drain hole (probably a varmint hole) to stick our foots into to claim a sumpit made.




In order to measure the difference in elevation from pit bottom to rim lowpoint, I purposely veered left (south) of the road. The low point on the rim is not easy to discern (it stays flat in an east-west direction for a long way). But at a good guess point I erected a cairn and made my measurement and it came out to 181 feet. Taking into account a margin of error, my guess is the pit is between 175 and 185 feet deep.



Alternate Approach
A shorter approach in terms of distance can be made from the rock climber parking lot on the north side of the rim here (see this picture). But what you reduce in distance you add in exertion because you’ll have to climb up a steep talus/scree field on the return. This would be a good approach if you are already there for rock climbing purposes and want to divert your attention to more holey matters.

Images

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