Pinhook Lake is a hidden gem that I ran across recently. It is
a great place to enjoy all of the indigenous and migratory wildlife. Please enjoy this area as I have and remember- leave nothing but footprints, take nothing but pictures and garbage (CITO!)
What Is An Oxbow Lake?
An oxbow is a crescent-shaped
lake lying alongside a winding river. The oxbow lake is created over time as
erosion and deposits of soil change the river's course. You can see how an oxbow
lake takes shape below:
(1) On the inside of the loop, the river travels
more slowly leading to deposition of silt.
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(2) Meanwhile water on the outside edges tends to
flow faster, which erodes the banks making the meander even wider.
(3) Over time or a larger event (see below), the
loop of the meander widens until the neck vanishes altogether.
Geology:
An Oxbow Lake is the result of a long geological/river process that is dependent on several factors:
1.Low slope- the elevation of the river that the “oxbow” was once a part of is not dropping very quickly
2.The riverbanks must contain rocks that are relatively easily
eroded as the river cuts into its banks.
3.Time! (OR #4)
4.At times, a larger event, such as an earthquake, flood, volcano (out west) or dam (human or natural occurrence) can trigger an oxbow lake overnight by diverting water to a new riverbed.
Pinhook Lake
This particular lake became an Oxbow due to the road being built next
to the river The choice was to either route the road around the crescent,
build a bridge over the meander, or fill in both
sections, creating a crescent lake to be separated from the river.
As luck would have it, the more cost efficient way was to fill it in.
This was the birth of Pinhook Lake and the changing of the St.Joseph River.
To Log This Earthcache please E-mail me the answers to the
questions below:
1) By observing the Photos and visiting the site, do you think
this Lake was formed through:
a) Time, b) Earthquake, c) Flood, d) Human- Built Dam
2) What man-made item is prominently displayed due north of the picture point
3) Due to the low slope of the Oxbow Lake, Take elevation
readings at Elevation point 1 (EL1), Elevation point 2 (EL2), the Posted coords, and the picture point (PP1). What is the difference in elevation between the points?
4) OPTIONAL- Take a picture of you, or your group holding your GPS at the
picture point- feel free to post in your log. If in a group, describe which one
you are.