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Photographer's Note

This view within Utah's Arches National Park, shows the "Parade of Elephants" on the right, and "Double Arch" on the left.

Arches National Park has the highest concentration of natural stone arches on Earth, with over 2,000. Conditions were ideal for arch creation here. The Entrada Sandstone was once a massive desert of shifting dunes of fine-grained sand. The sand grains are nearly spherical, forming porous rock when packed together. And just the opposite, the Carmel layer beneath the Entrada contains a mix of sand and clay. Clay being much smaller particles, pack into the gaps between sand grains, making the rock denser and less porous than the sandstone.
Deep beneath the surface is a thick layer of salts. Squeezed by the tons of rock above it, the salt flowed and bulged upward, creating long domes. The rock layers covering these domes were forced to crack, like the surface of freshly baked bread, into a series of more or less parallel lines.
The next arch requirement is 'water erosion', with the right amount of rain, averaging 8 to 10 inches a year. Keeping erosion working 24 hours a day all year long. Rainwater soaks into the porous Entrada Sandstone easily then slowly dissolves the calcite bond, rotting the rock inside out. Water puddles just above the denser Carmel layer where it erodes a cavity, like food trapped between your teeth. In winter, water trapped between the two layers expands when it freezes and pries the rock apart.
The result is large gaps in the rock, creating windows and arches.

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Additional Photos by Ray Anderson (photoray) Gold Star Critiquer/Gold Note Writer [C: 1077 W: 1 N: 2836] (11807)
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