1 March 2013

Landslide oddities part 3: the ground moves in mysterious ways

Posted by Dave Petley

First, my thanks to Ellen Hardy for pointing this one out.

Actually it is not really a landslide, but it is an example of the “strange” ways that the ground can behave.  The Southern USA has recently been affected by heavy rainfall.  In Leslie, Georgia, a homeowner was somewhat surprised when his empty swimming pool popped out of the ground.  WALB News 10 has the full story with a selection of photographs, although the best one is on the News 8 website, which also has a video:


From the WALB News 10 images:


An empty swimming pool is of course in effect a boat.  When the groundwater level becomes sufficiently high it will start to float upwards unless it is properly anchored down.  In this case it clearly was not.

This does illustrate some of the problems of interpreting the movement of landslides – sometimes strange things appear to happen through simple physics.  Landslide movement is usually controlled by buoyancy forces, which technically we term effective stress, operating in a very similar manner.