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Colluvial Fan: Glacier National Park

Colluvial Fan: Glacier National Park
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Colluvial Fan Profile: Glacier National Park by Shari Maria Silverman is licensed under a Creative Commons Attribution 3.0 Unported License.Colluvial Fan Profile: Glacier National Park

Colluvial Fan Profile: Glacier National Park: Photo taken in mid-September 2009

Glacier National Park shows a number of geological processes, including colluvial fans. The photographs above and below were taken along the trail to Hidden Lake, which is extraordinarily close to the continental divide. It’s elevation is extremely high. Much of the year, snow covers this area in a very thick blanket.

Obviously, these images not taken in snow, but on a warm summer’s day in mid-September, 2009.

The rock cliff is subjected to freeze/thaw conditions with moisture (snow). The freezing and unfreezing water expands and collapses, breaking up the rock. The rock gradually tumbles down the slope. The melting snow forms little rivulets, carrying some rock downslope.

The resultant, broken rock mass is colluvium. The fan you see in the pictures is a colluvial fan: a fan formed from colluvium.

Many of these rocks are angular, since most of them tumble from the slope, rather than transport by snowmelt. Water does not shape them. However, rocks closer to the rills you see in the photo below have some rounding conducted by the water trickle. If it were mostly water-made, this would be alluvium, not colluvium (you see alluvial fans from stream deltas quite often – NOTE: in the little stream rills, it shows small alluvial fans forming within the colluvial fan).

Note the larger rocks at the base of the fan in both the top and bottom images. This is due to the greater distance they can tumble.

Creative Commons License
Glacier National Park Colluvial Fan by Shari Maria Silverman is licensed under a Creative Commons Attribution 3.0 Unported License.Glacier National Park Colluvial Fan

Glacier National Park Colluvial Fan: Photo taken along Hidden Trail in mid-September, 2009.

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Creative Commons License
Colluvial Fan: Glacier National Park by Shari Maria Silverman is licensed under a Creative Commons Attribution 3.0 Unported License.


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