Tuesday, October 21, 2014

Week 6: Sedimentary Rocks

Arches National Park is a unique treasure that is just a few hundred miles away from us. It is the densest collection of natural stone arches in the world. 

Arches is made up of two main formations--Entrada and Carmel (or Navajo). The Entrada layer is porous sandstone, formed by a vast desert. The Carmel layer beneath is comprised of a mix of sand and clay, formed by desert-like conditions about 210 million years ago. It is more dense than the Entrada layer, which was formed by stream laid and windblown sediments about 140 million years ago.. 

Deep beneath is a layer of salt deposited in the Paradox Basic 300 million years ago. This salt has squeezed upwards, cracking large domes into the layers above. Rain water drains into the porous Entrada layer and dissolves the calcite that makes up the sandstone of both layers. During the winter, the water freezes and expands, causing more cracking and erosion from the inside.

Most of the formations visible at Arches National Park are the salmon-colored Entrada formation or the buff-colored Carmel formation. 

My little family visited the Double Arch last summer.

Arches National Park is located at: 
Coordinates38°41′00″N 109°34′00″W

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