"The Alligator" at Bryce Canyon
July 17, 2017
Photographer: Patti Weeks
Summary Author: Patti Weeks
The most striking images of southern Utah’s Bryce Canyon National Park to anyone peering down into its eroded amphitheaters are the stunning, red, and almost otherworldly-looking hoodoos. But also fascinating is a sparse layer of material, as seen in this photo looking north from the 8,300 ft (2,530 m) high Bryce Point Viewpoint. It looks as if someone has poured a layer of concrete along the top of one of the formations.
Through the generous assistance of Bryce Canyon National Park resident geologist Keith Moore, I've solved the mystery of this unusual formation. The nickname for this light-colored rock layer is The Alligator, named for its appearance from certain perspectives as a giant inflatable alligator pool float, lying on the more prominent reddish rock beneath it. This isolated rock layer is a concentration of dolomitic limestone, or dolostone (which contains up to 50 percent of the mineral dolomite), a protective, more erosion-resistant caprock found in the pink member of the c. 50 million-year-old Claron Formation of the Paunsaugunt Plateau.
The Alligator is roughly 700 ft (213 m) lower in elevation than Bryce Point and can be seen at the center left in the bottom photo of the Bryce Amphitheater. Park geologist Moore and Interpretive Park Ranger Peter Densmore created a pictorial illustration of this area to aid my research. It gives a perspective of the approximate elevation difference (click here).
Bryce Canyon is not actually a canyon, but rather an eroding, retreating plateau, and subsequently a series of amphitheaters. This wider view shows the large 12 mi (19 km) long, 3 mi (4.8 km) wide Bryce Amphitheater, which contains a broad gently-sloped syncline — a downward fold in the rock strata made over millions of years — in this case by compression of the thick layers of the Claron Formation. The small community of Tropic in the Paria River Valley is seen in the center right, and far in the background on the horizon to the northeast is the Table Cliff Plateau. These photos were taken on September 12, 2015.
Photo Details: TOP - Camera Maker: Panasonic; Camera Model: DMC-ZS7; Focal Length: 25.9mm (35mm equivalent: 158mm); Aperture: ƒ/5.0; Exposure Time: 0.0025 s (1/400); ISO equiv: 80. BOTTOM - same except: Focal Length: 4.1mm (35mm equivalent: 25mm); Aperture: ƒ/5.6; Exposure Time: 0.0020 s (1/500).
