Friday, April 25, 2014

Palouse Falls

The first year we lived here in Oregon, just after one of my geology classes had covered the Columbia River Basalts, a couple of my students took a weekend trip to Palouse Falls. They came back from their trip excited because they had been able to take what we had talked about in class and apply it to what they saw at the falls.

Because the Falls are nominally on the way to Spokane, WA or Moscow, ID, I would try and make a side trip to the falls on one of our trips for one of Sam's athletic competitions. Every time we would make the trip, I would plan on stopping on the way home, but something always came up (a snowstorm, a sick traveling companion, cold weather, a wrong turn, a snowstorm, lack of daylight due to a championship softball game, another snow storm) and I hadn't yet made it to the falls. I was finally able to make it this years when I had a couple of extra hours on a trip to Spokane.

The Palouse River cuts a narrow canyon through several prominent layers of Columbia River Basalts, and at the lower falls, there is an alcove where the river drops 56.6m (186ft) into a large plunge pool. From the falls, the river continues about 6 miles to where it empties into the Snake River above Lower Monumental Dam.
Lower Palouse Falls
It was a nice spring day, so marmots were out sunning themselves on the cliff side. It was a great lesson in camouflage that when we got about 5 meters away it took a while to pick the two marmots out from the dark basalt rocks along the edge.

Two marmots enjoy the spring sun.
From the main parking area, a short trail heads north to an overlook of the Upper Falls. From the overlook, a trail leads down into a wide side canyon and to the upper falls. Because we were limited on time, we only hiked down to the level of the UP Railroad grade for a view down the canyon.

View of Upper Palouse Falls from the Railroad grade.
At the base of the cascades of the North Falls, the river makes an almost 90 degree bend. This bend is because during the Ice Age Floods, the path of the Palouse River was diverted into a series of NW-SE trending faults.

The ancestral Palouse River used to follow the Washtucna Coulee to Kahlotus and Connell some 50 miles before ultimately discharging into the Columbia River near Hanford). But the volume of water resulting from the Ice Age Flood pushed the river out of its ancestral channel. The steeper gradient of the fault dominated channel allowed river to carve a deep enough canyon to capture the flow path after the floods receded. The abrupt transition from the ancestral channel into the nearly straight fault driven system can be seen in this Google Earth screen shot.
Google Earth image showing the fault channel of the modern Palouse River

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