Wednesday, May 4, 2011

Kettles in the Columbia Valley

Kettle lake or pond, Columbia Valley, Whatcom County, Washington

Kettles are a common feature along former glacial ice margins. Blocks of ice that get buried or partially buried in gravels and other debris melt creating pits in the landscape. There are numerous kettle areas in Washington State along former glacial margins.  

I took a trip out to the Columbia Valley in Whatcom County with David Tucker to check out some of the kettles on the valley floor. First, the Columbia Valley in question is in Whatcom County and should not be confused with the Columbia River. In fact this valley currently has no river. It formerly had a very large river during the late stages of the last glacial period.

These particular kettles stand out as the area is very flat and around at least a few of them there are no trees. As noted kettles are a common feature along ice margins where ice is melting back. There are numerous kettle areas in Washington State as well as along former ice margins where glacial ice was melting back. These areas tend to be lumpy landscapes of debris left behind by the ice. The Columbia Valley kettles formed within a former large river channel and as such the topography of the area is fairly level except for old river channel banks and the kettle depressions. 

Not all of the kettle depressions contain water. Only the ones that are deep enough that they intersect the ground water contain ponds or lakes. I have seen one of these kettles in the summer and the water was a fair bit lower. However, the Columbia Valley contains a fairly productive aquifer within the old gravel and cobble river valley. 
Two kettle lakes or ponds, Columbia Valley, Whatcom County, Washington

Columbia Valley in north Whatcom County

Columbia Valley showing former river flow path in blue

The LiDAR image of the valley shows the former river channels as well as numerous kettle depressions within the former river channel. The kettle depressions, are concentrated in only one area and are all located only within the deepest and most recent channel.  

LiDAR of Columbia Valley, blue arrows show flow direction of former river.

A major river flowed down the Columbia Valley during the late stages of the last glacial period approximately 12,000 years ago. The ice margin was located a few miles to the north in Canada. Multiple channels can be seen in the LiDAR image. I have always been intrigued by the fact that for at least a period of time some of the water escaped to the west and flowed down what is now Saar Creek and down through an area called South Pass. The LiDAR indicates that the river channel where the kettles are located is the deepest channel. A number of geologist have scathed their heads trying to figure out the timing of the events associated with this old river not only in Columbia Valley but downstream well. And the problem has some practical applications regarding landslides, slope stability, faulting, current river processes on the Nooksack River and Samish River and gravel resource areas in Whatcom County. The kettles provide some clues as to the history of water flow through this valley during the late glacial period.

Besides the great views of the kettles the former river bank channels are readily apparent not only on the LiDAR but out on the ground as well.

River channel edge as viewed looking from the former river channel

Road traversing up former river bank.

The valley floor is very rocky with lots of cobbles and boulders. Streams flowing off of the mountain sides disappear into the gravel and cobbles shortly after flowing off the mountain sides. Except for the kettles there are no surface water bodies in this portion of the valley. We enjoyed the short New England style rock wall with trees near one of the kettles.

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