Entrada Sandstone

July 31, 2013

Entrada SS Cliffs

Entrada SS Block1

Photographer: Gregory Lowell Vogt
Summary Author: Gregory Lowell Vogt

The photo at top features sedimentary layering of a cliff face in northern New Mexico. Chinle Formation sandstone (late Triassic) is found at the cliff base, while Entrada Sandstone (Middle Jurassic) and Todilto limestone (Jurassic) are further up the slope. Interactions with iron compounds have given the marine-formed Entrada sandstone its yellow, white and red colors. This rock is poorly cemented and breaks down easily. The bottom photo shows a block of yellow Entrada sandstone that’s tumbled down and rolled about 300 ft (100 m) from the cliff base. Wind and rain have broken down the block so that it now resembles a giant scoop of custard ice cream dropped on a hot sidewalk. Photos taken June 26, 2013.

Photo details: Top - Camera Maker: SANYO Electric Co.,Ltd.; Camera Model: CG20; Focal Length: 6.8mm (35mm equivalent: 38mm); Aperture: f/6.2; Exposure Time: 0.0025 s (1/399); ISO equiv: 50; Software: iPhoto 9.4.3. Bottom - same except Exposure Time: 0.0019 s (1/533).