14 May 2013

How to escape a landslide

Posted by dr-dave

Various news reports suggest that a couple in Alaska had a very lucky escape from a landslide on Sunday.  The best news report that I have come across is on Alaska Public Media, which also has this image of the landslide (credited to Kevin Knox):

Alaska Public Radio / Kevin Knox

Kevin Knox and Maggie Gallin were staying at Redoubt Lake Cabin in Alaska when, in Kevin’s words:

“We had just tied the boat up and Maggie was in the cabin, and it just let loose — a huge piece off of the side of the mountain. I yelled for Maggie to run, to get out of the cabin. We started running down the beach.”

“We were running along the lakeshore and got thrown into the water, trees kind of toppling on top of us. We both popped up three or four feet from each other. Then we got our wits about us and just tried to hunker down.”

Interestingly, the report indicates that they saw precursory rockfalls the evening before.  The couple were extremely luck to escape the landslide; sadly it appears that their dog was killed.  The couple were rescued by floatplane a few hours after the landslide.

The website of the former cabin suggests that it would have offered little protection from a landslide.  This is a Google Earth perspective view of the slope that failed:

..

There are few if any obvious signs of instability on the image. From the photo the left side of the landslide appears to be a wedge failure in bedrock; this in turn has destabilised regolith / colluvium on the right side.

It is quite rare to outrun a landslide in the way that these people have; they are exceptionally fortunate.