Tuesday, February 9, 2010

Sumas Mountian Slides and LIDAR

LIDAR Sumas Moutain

LIDAR (Light Detection and Ranging) http://en.wikipedia.org/wiki/LIDAR provides a bare earth image of the earth. LIDAR has proven to be a very useful tool for identifying large landslides and fault lines as well as a number of other key geologic features that are otherwise very hard to see in our heavily forested western Washington landscape. The LIDAR image of Sumas Mountain has taken up a lot of my time trying to figure out a very complicated mountain. I have used the LIDAR of Sumas Mountain for work, for geology curiosity and for just plain fun. One could plot out a bunch of field trips using LIDAR.

Sumas Mountain is located approximately 10 miles northeast of Bellingham near the Canadian border. As noted in a previous post title Whatcom County’s Desert, the Swift Creek landslide is located on the west slope of Sumas Mountain. Another post showed a LIDAR image of the slide.

The large image of Sumas Mountain shows other large scale slides on the mountain and a lot more! Only a few of the more obvious landslides are marked on the photo, but there are others and there are plenty of other features including plenty of drumlins, alluvial fans, an old sea level strand, bedrock structures, old river channels, a glacial outwash river valley, kettles and a fault line. The fault line was not identified until LIDAR imagery of the area was produced. See if you can find the fault. I’ll save it for a future post. Below is a closer view of some post ice age slides.

Post ice age landslides

The three large slides are each approximately 1,500 feet high and are deposited on the valley floor of a now abandoned glacial outwash valley. All three of these slides involve bedrock failures on a very steep glaciated valley wall. The slides are also located very close to a recently identified active fault line. I worked on a project to the north of these slides a few years ago prior to LIDAR. LIDAR would have made the project a lot less stressful.

Natural Gas Break Site

Approximately 10 years ago a large natural gas transmission line ruptured. The break ignited and lit up the area for about half an hour. Ground fractures to the north and south indicated a deep landslide was responsible for the slide. This was a previously unidentified slide. The pipe was rerouted further up the slope. At the time there was some debate as to whether the new route was off of the landslide or simply moved off of a portion of the slide that had moved. Whatcom County geologist Doug Goldthorpe thought the pipe was still on the slide and pushed for monitoring equipment to be installed. I reviewed some drilling records with cone penetrometers and agreed with Doug that the failure of the slide was beneath the new pipe route as well. We did not have LIDAR to review at that time, but looking at the image now, it appears that this is a complex deep slide structure that involves bedrock.

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