February 13, 2018

Going with the Flow

Posted by larryohanlon

Sometimes you have to build the field in the lab. At the Virginia Tech Active Tectonics and Geomorphology Lab researchers do just that. This is the latest in a series of posts shared from their blog. More of their posts can be found here.

Words by Lisa Whalen, Model by Phillip Prince

Images credit: British Geological Survey


Sandbox models aren’t just for mountain building. In this video Phillip Prince replicates landslides.


A translational landslide is when rock or soil moves down-slope along a plane of weakness like a joint, fault or bedding surface. Best illustrated with chocolate and a weaker layer of caramel:



A rotational landslide on the other hand has a curved surface of weakness and moves large blocks of material that tend to rotate backwards as they move.



Here in southwest Virginia are some of the largest known landslides in the world, with one slide reaching almost 3 miles long. You can learn more about “The Mountain that Moved” on the USGS site about Sinking Creek Mountain. The landslides occurred in the Pleistocene, but weren’t discovered until the 1980’s because the enormous size of the landslides obscured their presence. Today they can be identified partly through different vegetation and the presence of springs and pare visible from many of my favorite hiking areas. They may have been caused by erosion or even by earthquakes.

As an aspiring mountaineer another way to think about translational landslides is to think of slab avalanches. In this case you have layers of snow separated by a weaker layer. Weather, more snow, or people (such as in the video below) can tip the scales of the forces that are keeping the layers of snow coherent and trigger an avalanche.