The Lesson:
Oxbow lakes are simply a type of lake that was once a part of bend(or meander) of a river that has become isolated or separated from the main channel, making its own body of water.
How does this happen? How does a river just change like that?
Erosion:
Meanders in a river grow through erosion and sediment deposition. They grow laterally as the faster flowing outside bend erodes away and the slower moving inside bend deposits sediment. Over time this will create a narrow neck in the meander. When the loop gets to large and starts to consume too much energy (friction), the river will eventually find a less energetically "taxing" shortcut(through the narrow neck), and a part of the old channel will be abandoned and becomes an oxbow lake.
Flooding:
River flooding can also help with the creation of oxbow lakes. It can be caused by heavy rains, snow melting upstream or any number of other ways. When this happens it can give the river the opportunity to create a new channel through the narrow neck of a meander as the flood waters create new levees and raises itself over the floodplain. The slope and the transport power of the stream decrease, the channel fills gradually with sediment, and finally (often during a flood) the river will breach its levee and follow a steeper path down the valley.
Bonus Info:
An oxbow is a part of the yoke for a team of oxen that is shaped like a crescent or the letter U. This piece of the yoke is called a bow. The reference may be a little dated, and most of us have never seen a team of oxen in real life, but in geography, the name sticks. An oxbow lake is a crescent-shaped lake (yes, it looks like the bow of an oxen yoke) that forms to the side of a meandering river.
The Location:
The posted coordinates will lead to a boat ramp in Grayville Illinois. Here you can see a great example of a large oxbow lake.
Here is an overhead view of your location:
See how the lake was once part of the Wabash River? The meander grew a very sharp curve here forcing the Wabash river to cut it off as described above. If the lakes water level gets high enough the lake will connect back to the river by a run off stream on the south end. Major flooding in the early 1900's also helped form this oxbow lake(flood level shown on the nearby monument).
There are 2 other waypoints you will need to visit nearby in order to answer all the questions.
There is a plaque discribing a hotel at this location when the oxbow was still part of Wabash River at one waypoint and a monument with indicators of major Wabash River crest levels from the past at the other.
The Questions:
Send the answers to these questions via email to me.
1. What years are on the crest monument?
2. About what year did the Wabash House open?<<<<This is cool to know because it shows the oxbow was still a part of the river not so long ago.
3. Look out to the southeast of the lake when standing at the posted cords. Depending on the water level you will most likely see sediment beds raising from the water. How was this most likely deposited there?
4. What happens on the "outside bend" of a meander helping it grow?
5.(Optional) Post a picture of yourself and your phone or GPSr and the oxbow lake in the background. This is nice to have to verify your visit and also see all the awesome geocachers who have found my caches.
If you have an questions or trouble with this EC feel free to send me a message! Cache on!