GOOSENECKS STATE PARK
I visited the Goosenecks State Park in Utah for my travel
entry on river erosion. The overlook
gazes down on the San Juan river a thousand feet below. This is one of the better examples of an
entrenched river meander in North America.
The river flows a distance of six miles while only traveling, as the
crow flies, one and a half miles. What I
saw at the park is the result of three hundred million years of geological
activity where the San Juan, head-watered in the San Juan mountain range in
Colorado, has harnessed the erosion of hydraulic action to abrade the sediment
and carry it away. The flow velocity is measured
between five hundred and eight thousand cubic feet per second throughout the
year with ninety percent of the water in the river at the park coming from
Colorado. Erosion has transported larger
particles in a process called bedloading.
Smaller particles, like sand grains, are moved in a process called
saltation. You can see the suspended load,
like silts and clay, in the color of the river. The S shaped curves of this meandering river have
almost cut a path connecting the bend. This is known as a cut bank and is very noticeable here in the park. It is the result of higher flow
velocities on the outside of the river bend and "cuts" away the material. Low velocity, on the inside of
the meandering curve, results in the deposition of point bars. These are where the material is deposited and can be noted as shallow areas of the river on the "point" of each turn. Both can be seen in the pictures below. Runoff increases all these erosion
processes. The geologic makeup of the area
is mostly sandstone with some shale. To
a lesser extent, there is even some limestone, so acidity is also a factor in
this erosion. In a few million years,
this canyon will continue to form and change the river’s course even more than
what I saw today.
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