The Windows, Arches National Park, Utah, USA, 25th October 2014.

Arches National Park has the highest concentration of natural arches in the world.  The area has an unusual geology in that beds of Jurassic sandstone and mudstone were underlain by beds of salt.  The salt eroded away due to the ingress of water as the Colorado River established itself in the area, causing undercutting, fracturing and faulting of the rocks above.

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The first stage in the formation of an arch can be the generation of a fin.  The desert region can be very hot in the day and very cold at night.  Even though it is a desert, there can be water present in cracks in the rock, which then intensifies those cracks through the heating/ cooling process slowly over time.  In this case, fracturing leading to the formation of fins can also be in part due to the stresses on the rock due to the dissolving of the underlying salt layers.

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Once the fins are formed, then the holes appear through a slow process of the erosion of the face.

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Ultimately, of course, the arches will collapse, though hopefully not when people are underneath.

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Looking up.

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Still the same arch, I think North Window.

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I think this is South Window.

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North Window again.

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Turret Arch.

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Turret Arch.

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Looking North from Turret Arch, perhaps towards the parade of Elephants.

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Perhaps looking South.

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Turret Arch.

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Looking East from near South Window.

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Turret Arch.

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Trivia point:  This is post number 500 in this blog, though there are less than that on display as I have hidden or removed some of the temporary ones.

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