Channels, Pillows and Giant Ripples
[25.4 MM 257]
This view to the southeast shows Hanning Butte and Magnison Butte. These are granite hills that were able to withstand the floodwaters. Steptoe Butte, some 60 miles south, is also made of granites that stood higher than the basalt flows that formed the Columbia Plateau. The plateau is actually more like a basin or saucer since the weight of the basalt made it sink into the Earth's crust.
[32.7 MM 250]
We enter Davenport and soon turn south (left) onto State Highway 28.
[33.9 MM 130 State 28]
We are now in one of the flood channels of the Channeled Scablands.
[45.8 MM 118]
Soon we are entering the farm community of Harrington. Just out side of town we start to leave the channel and travel on a loess-covered island.
[58.4 MM 105]
This weathered basalt in the road cut looks very different than the pillow basalt of the next road cut. Pillow basalt is formed when lava flows under water. The light colored material surrounding the basalt is palagonite, a soft yellowish rock full of clay. Formed by hot basalt and steam it is mixed in with sand and mud.
[63.5 MM 100]
A geologist has to be careful when identifying patterns and landforms. Erosion, weathering, wind, water, heat and other natural actions can make it hard to determine just what happened thousands of years ago. In the image below, do you see lap marks from an ancient lake, flood water carved ledges, or wind blown ripples? What else might they be? Click on the image or here to find out or see answer below.
[64.1 MM 99]
Giant ripples can be seen in the flood gravel bar on our left. Current ripples are found in the beds of flowing streams and rivers and are similar to "washboard" gravel roads in that the ripples are from side to side and have regular patterns and distances between them. Ordinary ripple marks are one-half to one and a half-inch high, however, this flood region has current ripple marks up to 30 feet high.
[69.9 MM 93]
Odessa is a small community that will turn 100 years old in 2002. Founded by German Russians, they celebrate Deutschesfest the third week of September. This festival is similar to Octoberfest festivals elsewhere in the world. For bird watchers the US Department of the Interior, Bureau of Land Management has a list of "Birds of the Channeled Scablands of Eastern Washington."
[71.0 MM 91]
Floods deposited the gravel in this quarry just outside of Odessa. You can see the larger more coarse deposits and rock up to 4 inches in size that settled out first. We continue our trip by crossing a train of giant ripples.
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.
- Channeled Scabland
- Area in Washington state where huge floods made channels in a large, deep basalt flow. Named by J Harlan Bretz during the 1920's in various publications. See also Channeled Scabland and Glacial Lake Missoula.
- 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.
- Pale yellow, glassy material that forms when hot steam and other gases contact water during a lava flow. Sand and clay is usually mixed in as well.
- Pillow Basalt
- Basalt formed underwater or as a basalt flow contacts a river or lake.
Kids' Cosmos… Expanding Minds Beyond the Limits of the Universe
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