|Dusty Lake in Potholes Coulee|
Access: Washington State Parks Discovery Pass required ($10/day, $30/annual); trailhead at the end of a good gravel road
Washington State's Columbia Plateau can seem largely featureless and drab for drivers traveling through the region along I-90, but just a few miles off the interstate lie some fascinating landscapes shaped by the many violent geological phenomena. Hidden among the desert and reclaimed farmland of Eastern Washington lie dramatic coulees cut into cliffs of columnar basalt. Nowhere is this landscape more beautiful and easily explored than at Potholes Coulee with the hike to Ancient Lakes, just southwest of Quincy. On the dry side of the Cascades, Ancient Lakes usually stays at least somewhat sunny when winter rains drench Seattle. The hike itself is generally easy and flat and recommended to anyone in the area with a few spare hours, as well to Seattle residents hoping to rediscover the sun during the drabbest, stormiest days of the year.
I headed to Ancient Lakes with two friends from Seattle on a rainy Sunday. We followed I-90 west for two hours past Snoqualmie Pass, Ellensburg, and Vantage to George, where we exited the interstate at Exit 149 and followed Route 281 north. We followed 281 through the farmland of the Quincy Basin to the junction with White Trail Road; we turned left onto White Trail Road and followed it around a wide bend to the right until we reached Road 9; we turned left onto Road 9 and followed it downhill past views of the Columbia River and its beautiful gorge all until it turned into a gravel road; we continued on the gravel road until it dead-ended at the trailhead for Ancient Lakes, where a sign indicated that we should display a Discover Pass.
The trail was simply a continuation of the gravel road. We followed the wide gravel path south through the sagebrush, following the base of the a set of columnar basalt cliffs that rose prominently to the east. About half of a mile in, the cliffs to the east opened up to expose Potholes Coulee, a wide canyon filled with shrubs cut into the surrounding basalt landscape. We skipped the initial path leading left into the coulee but took the second, narrower trail that branched off to the left. There were numerous use trails in the coulee that split apart or came back together; it was difficult to keep track of which exact path we were on. However, for the most part, this mattered little; we followed the general direction of hiking deeper into the coulee.
The layers of regularly shaped hexagonal columnar basalt that formed the walls of the coulee were the result of massive volcano eruptions in what is now the Pacific Northwest around 15 million years ago. These eruptions differed greatly from the eruptions that formed the modern Cascade stratovolcanoes; instead, the ancient eruptions occurred in the form of flood basalts, in which lava emerging from the volcanic source covered the entire Columbia River Basin, forming the Columbia River Flood Basalts. Multiple eruptions from this source led to many layers of flood basalts, each set atop the previous eruption's layer. Quickly cooling mafic lava, such as that found in the Columbia River Flood Basalt eruptions, contracts to form joints between sections of exposed lava, eventually forming the vertical columns so commonly seen in Eastern Washington. The source of these massive flood basalts that covered much of the Eastern Washington and Oregon is still disputed; one suggestion is that the basalts formed from an earlier manifestation of the Yellowstone Hot Spot, which may have later migrated across Idaho to form the Snake River Plain as the North American Plate moved before reaching its current position beneath the hot springs in Wyoming.
|Waterfall in Potholes Coulee|
|First pond in the coulee|
|Waterfall at the head of the coulee|
It took geologists a long time to come with grips with the idea that the desert coulees of the Columbia Plateau were carved out by massive Ice Age floods. After all, modern geology was born with James Hutton's principle of uniformitarianism- the idea that geological processes occuring today are the same as ones that have occurred in the past. Geologist J Harlan Bretz first hypothesized that the coulees and the Channeled Scablands of the Columbia Plateau were formed by massive floods, but was written off by more established geologists as a lunatic, a fool, or an amateur. If massive, catastrophic floods of the scale Bretz proposed never occur today, they reasoned, why and how would they have occurred in the past? Yet increasing evidence pointed to the validity of Bretz's theory: both the head of Potholes Coulees and Dry Falls on the Grand Coulee showed signs of having been ancient waterfalls and the discovery of a "bathtub ring" along the mountains above the Clark Fork in Idaho and Montana validated the existence of glacial Lake Missoula. Today, the combined effects of the Columbia Plateau flood basalts and the the Missoula floods on this landscape make it one of the most geologically fascinating areas in the country.
The waterfall that today flows down the head of Potholes Coulee is fed by a non-natural source: it is only a year-round waterfall because of irrigation runoff from the Bureau of Reclamation's Columbia Basin Project. The Columbia Plateau is a desert with just enough water to support sagebrush and tumbleweed, but the Columbia Basin Project turned the area into farmland. A massive works project during the Great Depression led to the construction of the Grand Coulee Dam on the Columbia River. Today, river water is stored in Banks Lake and reaches farms near Quincy, Ephrata, and Moses Lake through irrigation canals, allowing for agriculture in an arid land. The agricultural benefits are clearly great, but the price tag of the project and the environmental consequences on water quality and Columbia River salmon populations have perhaps been equally large.
After lunch at the foot of the waterfall, we retraced our steps along the lakeshore back to the ridge separating the three lakes. From the ridge, we followed a trail that traced the west lakeshore of the southeastern lake, which had a particularly round and pleasant shape. We followed the trail past the lake and briefly uphill and found an unmarked trail heading off towards the left. At this junction, we decided to check out what we would find on the spur and left the wider main trail.
The spur began the first steeper climb of the hike; we soon realized it wasn't actually a spur trail but instead a longer trail that followed one of the higher benches on the coulee. We found a small cave to the right of this trail: the cave wasn't deep but allowed us to explore a small basalt overhang that must have been carved out by the Missoula Floods. Inside the cave, we could clearly make out the polygonal shapes of the basalt columns.
|Cave in the basalt|
|Looking towards Dusty Lake from Potholes Coulee pass|
|Columnar basalt in Potholes Coulee|
The landscape of Potholes Coulee is remarkable and geologically fascinating. While many hikers may prefer to stay in the Cascades to enjoy Washington's alpine terrain, I found the desert to be equally interesting and enjoyable, if in different ways. Don't write off the desert: go and explore this terrain of eroded basalts and lakes.