Wednesday, September 29, 2010

Esker Near Lake Padden?

Another UPDATE: See below
UPDATE: See below
I paid a visit to my local County Council last night regarding Lake Padden, a lovely gem of a lake in south Bellingham. Essentially every time anything comes up regarding that lake either the City Council or County Council gets to see me. Beforehand I was checking out the watershed boundaries using LIDAR imagery when besides the really cool folding apparent within the Chuckanut Formation, I spotted an interesting feature snaking across the slope to the northeast of Lake Padden. I have not ground truthed this feature, but it sure looks like it is an esker.
Possible esker near Lake Padden
The esker is the squiggly line across the otherwise smooth slope.
Clicking on the image will make it a lot easier to see.

Eskers are formed by water flowing underneath glacial ice, but instead of eroding downward into the ground surface, the water erodes upward into the ice. When the glacial ice melts away an inverted stream bed is left behind. LIDAR is pretty good at spotting eskers. They are otherwise hard to see in western Washington where the land is covered with trees.

Eskers are part of the National Natural Landmark designation on the Waterville Plateau in central Washington. The Waterville Plateau is west of the Grand Coulee. The continental glacial ice margin was located across this plateau and wonderful eratics and terminal moraine features as well as eskers cover the area north of Highway 2. The following Google earth Images are of a esker near Simms Corner.

Esker on the Waterville Plateau
Oblique view of esker showing inverted stream bed.

Update: Dave Tucker emailed that he knows of one geologist that did check out the possible esker. He thought it might be a morainal feature. I'll throw out another theory I have that the feature appears to be just below the crest of the slope from the north and may be a small depositional feature as the glacial ice rode over the crest of the slope from north to south. Anyway I look forward to hearing from some ground truth views of the feature. I do know that there is a morainal like feature to the southwest of the word Padden on the above map. As always thanks Dave for the info.
Another Update: Doug Clarke (personel communication, 2010) interprets the feture as morainal. Thanks Doug.
Two thoughts on this. One is the intent of this blog is to share observations so the input is greatly appreciated. And two, it is clear that LIDAR helps identify features that can be pursued in the field. Now I am thinking about what type of moraine and why is it there. But keep in mind that not all questions and features are readily answered or explained. Think Mima Mounds or just exactly what happened to the pronghorn antelopes in eastern Washington.


a fan (non-alluvial) said...

Would really love to see a detailed post on the suitability (or lack of it) for dense development on the Yew Street slopes above Lake Padden, from a geologist's perspective, the science.

San Juan Blvd has lurked out there as long as I've lived in Bham, and that is a long, long time now. The proposal has been pushed, laughed at, downgraded, resurrected, buried, reborn. Whatever stakes have been pounded into its heart, the zombie idea keeps shambling.

It goes to an idea I have that good ideas are fragile and easily harmed. Bad ideas can live for thousands of years and there just really is no way to kill them.

Dan McShane said...

Yes, bad ideas have a tendency to never go away. My own experience is that when a bad project that was once approved gets axed, there is very little notice except by those associated with the bad project. Another tactic for bad ideas is to spend a little money on it at first. From then on that money will be viewed as wasted unless the project is completed.