Gravel Bars and Buttes Along Crab Creek
[74.6 MM 89]
Another example of giant ripples is in the gravel bar on our right.
[74.6 MM 89]
To the north is another flood channel (coulee).
[89.6 MM 74]
Up ahead through a road cut we view the Crab Creek Valley near Wilson Creek. The irrigation of the area brings a lush green valley out of the semi-arid desert.
[93.3 MM 70]
We are at the junction of Highway 28 and Wilson Creek Road (to the right). The view to the west includes well-developed sloping gravel bars and flat-topped buttes along Crab Creek. Just upstream of this point Crab Creek is a meandering stream cutting through the basalt just as it was before the flood formed the channel in this area. Take a few moments to view the buttes and gravel bars in the distance and the fertile Crab Creek valley. We continue on Highway 28 and cross Crab Creek Flood Bar #4 where deposits of gravel of larger size changes to smaller sizes downstream.
|"Prior to catastrophic flooding, Crab Creek was apparently a meandering valley cut into the Yakima Basalt (one of the many Columbia Plateau basalt layers). The valley sides and interfluves were thickly mantled with loess as in the modern Palouse Hills near Pullman (WA). Just upstream from this stop Crab Creek preserves the forms of pre-flood valley meanders." [Field Trip 2]|
[100.4 MM 60]
To our right across the small lake we can see where an irrigation canal has cut through flood gravels for several hundred feet. Soon we cross Crab Creek and enter the town of Stratford.
[101.8 MM 59]
In the road cut on both sides we see white clay-like lakebed deposits. These deposits contain silt, sand and dead marine animals and plants that settled on the bottom of an ancient lake.
[102.9 MM 58]
We are at the junction of Highway 28 and Pinto Ridge Road and turn right to proceed north on our trip. Just ahead [102.9] we cross the main canal of the Columbia Basin Project.
Here are some basic terms used in the tour. Find more geology terms in the Glossary.
- Volcanic rock caused by partial melting of the Earth's crust.
- Long winding channel cut through lava formations. A term primarily used in the northwestern United States.
- Current Ripple
- Mark left on streambed from water current usually less than an inch high and a few inches between the tops (crests) of each ripple. The giant ripples from Lake Missoula floods are as much as 35 feet high and several hundred feet between.
- Fine dirt deposited by wind usually from arid or glaciated areas.
Kids' Cosmos… Expanding Minds Beyond the Limits of the Universe
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