27 July 2012

The amazing vanishing garden

Posted by Dave Petley

Komonews ran a slightly perplexing story yesterday about a couple living in Whidbey Island, which lies a little to the north of Seattle in Washington State, USA.  In the link there is a video that shows the rather interesting retrogressve failure that is steadily eroding away their garden.  With luck and a following wind you might be able to see it below:

It is not at all clear to me why this should be happening at this site at this time.  The owners describe a geysir 25 feet (about 8 metres) high, which suggests very high pore pressures developed in the ground at this location.  This presumably indicates a change in subterranean plumbing, but the cause is far from clear.  The process now appears to be a set of retrogressive failures that are slowly but steadily devouring the garden.  There is a good article on the geology of Whidbey Island here – it is formed of glacial deposits that are likely to be highly erodible.  Indeed, Whidbey Island has a long history of landslide problems, suggesting that one should not be too surprised that a failure can occur at this location.  It is unlikely that the owners can do much except wait for the system to stabilise naturally.