Saturday, September 28, 2013

Big Landside Hints

Posting has been a bit limited of late due to field work and deadlines.
I visited a large slide area on Hood Canal recently. I had been to the same slide area a few years ago before it reactivated and identified a clay unit that is rather consistently associated with a number of deep-seated landslides in the area. With the more recent movement it really doesn't take a geologist to know something is amiss. Lots of obvious and not so obvious hints.
The first picture above shows a fairly mature cedar that is tilted well out of plumb. The road also has a bend where it crosses onto the failure area and has been off set from its original straight path. Note the thick growth of horse tail indicating wet soils at depth.

The fence has been off set about 15 feet as a block within the slide complex moved at a faster rate than another block.

Silt/clay unit that is unraveling and is the cause of the failure 

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