Beware of Bent Trees
In Michigan, United States
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Beware of Bent Trees
Cache Summary: Bent trees give us a clue that this hill is on the move. This site is located on Michigan Tech University’s hilly campus in Houghton, Michigan. The slope is between Phoenix and Cliff Drive. Park in the parking lot across the street.
Figure 1. Bent trees on a slope. Photo by R. Joyce
Cache Coordinates: N 47° 07.256 W 088° 33.108
What does the shape of these trees tell us about the movement of this slope?
Trees growing on an unstable slope may have curving trunks. Plant roots tend to grow in the direction of gravity and shoots and trunks in a direction opposed to gravity. This plant movement is called geotropism.
Figure 2. Source: http://cbse.myindialist.com
If the soil in a slope is moving downward, the trees on this slope will tip downward. As the tree continues to try to grow upward, the trunk will show a curve. The degree of bending could indicate the rate or amount of movement of the soil. In this site, some trees are bent a lot and others not at all. Why could this be?
Figure 3. Source: http://www.indiana.edu/~geol116/week10/wk10.htm
Bent trees on a hillside can be a clue that the hill is slowly sliding downward under the pull of gravity. This downward movement can occur at rates of only a few inches a year, or it can occur very rapidly, as in a landslide. Bent trees can be a warning sign that a slope is not stable and may be a risky place to build. This steep hill is composed of glacial sediments, material deposited by glaciers. How fast do you think this hill is moving?
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Where will this hill end up? Please make a claim, support it with evidence, and explain your reasoning.
Earth Science Literacy Principles Big Ideas: Big Idea 4: Earth is continuously changing. Big Idea 4.8 Weathered and unstable rock materials erode from some parts of the Earth’s surface and are deposited in others. At this site in Houghton the bent trees on this slope are evidence that this hill is eroding. Visit http://www.earthscienceliteracy.org/es_literacy_22may09.pdf for more information on the Big Ideas.
Common Earth Science Misconceptions: A common misconception is that the Earth has always been pretty much the way it is now. This site gives evidence of a landform that is moving and changing. In this case, the change has happened in the last fifty years, a time scale that is easy for us to grasp. Visit http://hub.mspnet.org/media/data/MiTEP_List_of_Common_Geoscience_Misconceptions.pdf?media_000000007297.pdf for more information on Common Earth Science Misconceptions.
Dunning, Jeremy “Mass Wasting” G-116 Our Planet and its Future Indiana University July 20, 2012 <
“Landslide Info” North Carolina Geological Survey July 20, 2012
"Movement due to growth" CBSE Tutorials June 24, 2010. July 20, 2012 <http://cbse.myindialist.com/biology-x-control-and-coordination-coordination-in-plants-movement-due-to-growth/>
(No hints available.)
Last Updated: on 9/16/2017 7:22:56 AM Pacific Daylight Time (2:22 PM GMT)
Coordinates are in the WGS84 datum