Palmetto Oxbow EarthCache
Hidden : 10/17/2013
Difficulty:
2.5 out of 5
Terrain:
1.5 out of 5

Size: Size: other (other)

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Geocache Description:

A river feature Earthcache at Palmetto State Park's Oxbow Lake Trail about an Oxbow Lake.

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Through water erosion (the process by which the earth's surface is worn away) and deposition (the geological process by which sediments, soil, and rocks are added to a landform or land mass), the San Marcos River channel creates many different hydrologic features. Use the definitions, images, and Oxbow Lake Trail to answer the questions. Please Message me your answers. Any logs without answers will be deleted.

An anabranch is a section of a river or stream that diverts from the main channel or stem of the watercourse and rejoins the main stem downstream.

Oxbow lakes are stillwater lakes. This means that water does not flow into or out of them. There is no stream or spring feeding the lake, and it doesn't have a natural outlet. An oxbow lake gets its name from the U-shaped collar placed around an ox's neck to which a plow is attached. It can also be called a horseshoe lake, a loop lake, or a cutoff lake.

Water channels are not straight, because friction slows the water interacting with the walls of the channel. Inertia throws the fastest moving water against the outside of the curve. This "cutbank" experiences erosion. Near the inner bank, the quietest waters accumulate. These deposit sediment in a "point bar". The net result of erosion on the outer bank and deposition on the inner one is for the channel to migrate in the direction of the outer bank.



In map view, the result is a river that meanders in a series of broad loops, and the meanders are self perpetuating. They are limited by the fact that they bump into one another. A meander loop may cut itself off. When this happens, water is faced with a choice: Go the long way or go the short way? Most water chooses to go the short way, i.e it takes the path with the steeper gradient. Thus, as the erosion and deposition continues, the curve becomes larger and more circular. Eventually, the loop of the curve reaches a diameter of approximately five times the width of the stream and the river begins to cut the loop off by eroding the neck of the loop. Eventually, the river breaks through at a cutoff and forms a new streambed. Sediment is then deposited on the loop side of the stream, cutting off the loop from the stream entirely, and the meander loop is abandoned, forming an oxbow lake.



In their evolution, Oxbow lakes lose their distinctive crescent shape due to silting and sediment build-up. Frequently, they become swamps, bogs, and marshes, and over long periods of time, they often dry up as their water evaporates leaving a meander scar on the landscape.




To log this Earthcache, answer the following questions:

#1. Begin at Waypoint #1, which is just north of the restrooms, east of the bridge on Oxbow Lake Trail. Briefly describe the lake evolution here using the information you learned in the description and visual observation at the site (one or two sentences).

Follow the road north and west to access the Oxbow Lake Trail immediately west of the bridge to reach waypoint #2. Please be sure to make mental observations about the north shore to help you answer question #3.

#2. Waypoint #2. Briefly describe the lake evolution here using the information you learned in the description and visual observation at the site (one or two sentences).

Continue to follow the Oxbow Lake Trail south and east to return to waypoint #1. Please be sure to make mental observations about the south shore to help you answer question #3.

#3. Based upon your visual observations of the bank on the north and south sides of the trail and the descriptions of oxbow lakes above, which shore was the cut bank and which was point bar? How can you tell?

#4. Based upon what you read in the description and saw around the lake, is Palmetto State Park's lake really an Oxbow Lake? Why or why not?

Placed by a proud



Bibliography

Dreyer, Lacey, George Ford, and Patrick Laird. "Utilizing GIS to Determine Oxbow Lakes and Meander Scars Along the Neosho River in Coffey County, Kansas." Introduction to Geospatial Analysis Project. Emporia State University, 8 Dec. 2003. Web. 20 May 2013. http://academic.emporia.edu/aberjame/student/laird2/gisproject.html.

Merck, John W., Jr. "Introduction to Physical Geology Syllabus." Introduction to Physical Geology Syllabus. University of Maryland, 12 Apr. 2010. Web. 13 May 2013. http://www.geol.umd.edu/~jmerck/geol100/lectures/29.html.

Rutledge, Kim, Melissa McDaniel, Diane Boudreau, Tara Ramroop, Santani Teng, Erin Sprout, Hilary Costa, Hilary Hall, and Jeff Hunt. "Oxbow Lake." National Geographic Education. National Geographic Society, n.d. Web. 13 May 2013.
http://education.nationalgeographic.com/education/encyclopedia/oxbow-lake/?ar_a=1.

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