Norridgewock Landslide EarthCache
Hidden : 7/9/2010
Difficulty:
1.5 out of 5
Terrain:
2 out of 5

Size: Size: other (other)

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Geocache Description:


Landslides, common in Maine's history, are caused when gravity pulls on the ground mass of a slope. They can occur when the conditions of unstable soils, a high water content and a high degree of slope are present.

As the land moves, usually a few millimeters each day, tension cracks occur in the earth. As tension increases combined with high amounts of water, the land increasingly moves and eventually slides away from the slope.




The Norridgewock landslide occurred on July 9, 2009 along Sandy River Road. The land slid into the river at a bend in an unpaved section of the road just east of Sandy River.



The geology of the area consists of three soil layers. The bottom and middle layers are granite bedrock topped with glacial till. The top layer is a marine-clay silt. About three feet of road fill makes a 4th "cap" layer.



What caused the landslide? Well, the slope's base soils, through erosion, undercut the road edge causing an oversteep. High rainfall on the slope transformed the underlying marine clay into an unstable lubricated state. The combination of slippery marine clay and an undercut slope sent the land sliding into the river.

The slide is about forty feet long and ten feet high.



To log this earthcache, please submit your answers to the following questions:

1. In your estimation, is the flow of the river slow, moderate or swift?

2. Several conditions lead geologists to believe this site to be at risk for future landslides. In your observations, what conditions do you see that are possible landslide precursors? (look at the trees and road surface.)

3. In your estimation, what is the relief (height) of the river bank?

OPTIONAL: Photographs of yourself or surroundings will be met with giddy earthcache-geek excitement.


FTF honors go to bfrueger!

Resources and Credits:
David Petley, Dave's Landslide Blog
Maine Geological Survey
Natural Resources Canada



Placed by a member of D.A.W.G.S. - Denton Area Wayward Geocache Seekers.

Additional Hints (No hints available.)



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