Tuesday, October 6, 2015

Back Eddy at Pangborn Bar

Apples heading to the warehouse above the Columbia River valley

There is a lot of landscape in the above picture of the Columbia River valley downstream of Wenatchee. The view is looking west up the valley towards Wenatchee which us around the corner and out of site on the right. On the right is the edge of picture as well as the foreground is Pangborn Bar. Pangborn Bar is a huge gravel bar deposited by early ice age floods that surged down the Columbia River. The green valley floor was formed by later ice age floods that created a back eddy that carved off a bit of the older gravel bar.

The picture really fails to capture the scale of the landscape. And in truth, even standing and looking at the view is only a modest improvement. The scale of the features is to hard to take in and our minds have a hard tome reading landscapes of this scale. The ice-age floods left such massive features they are hard grasp.

DEM showing back eddy with curved blue line

Note in the DEM, the Pangborn Bar is about 8 kms long. Note the large old landslide complex northeast of the bar. A classic feature in over steep basalt lava flows of eastern Washington. Southwest of the river is an even larger landslide complex. It is old, but parts show evidence of relatively recent movement.

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