LANDSLIDE IN KEENE, NY
Progression of landslide from May 10 - May 31, 2011.
A landslide taking place since May, 2011 is now considered to be the largest recorded landslide in New York State. Over 82 acres of earth are moving, albeit slowly, but steadily. Unlike the movie version of landslides in which rocks and boulders and fast-moving earth quickly destroy everything in its path, most true landslides are slow-moving. Early measurements taken by the New York State Geological Survey indicate the hillside moving downward at the rate of about 1 millimeter an hour along a mile-long scarp. This is considerable when you take into account that the foundation of several homes located along the site are being moved as well.
After the initial period of relatively fast movement this spring and early summer, the landslide has slowed. As the summer season has progressed groundwater has been drained from the system and the rate of movement is about 1-2 mm per week. Although dry weather has helped to slow the slide, rain and snow from upcoming seasons could integrate into the well developed fractures in the ground and continue to destabilized the area.
In the News:
About the Keene Landslide:
Read more about Landslides and their history in New York State
The condition of the landslide taking place in Keene Valley is a type of slide known as a "rotational slump." Rotational slumps occur when a slump block, composed of sediment or rock, slides along a concave-upward slip surface with rotation about an axis parallel to the slope. Rotational movement causes the original surface of the block to become less steep, and the top of the slump is rotated backward. In this instance, the snow and ice melts, coupled with recent heavy rains, are believed to have caused the "complex rotational slide," in which the ground drops and rotates. The hillside itself is comprised mostly of layers of silt, clay and sand along with an unsorted mix of boulders and fine sediment.