The Encyclopedia Americana (1920)/Crater Mound, Arizona

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CRATER MOUND, Arizona. This feature in the plains 25 miles due west of Winslow, Ariz., formerly known as Coon Butte, is one of the most remarkable natural wonders in existence. It consists of a crater 600 feet deep and 400 feet in diameter surrounded by a rim 100 to 150 feet high. This rim consists of loose fragments of rock and sand from the hole. The walls of the hole are limestone (Kaibab) and sandstone (Coconino), more or less upbent and shattered. The relations are shown in the figure.

Americana 1920 Crater Mound Arizona section.jpg

Section through Crater Mound, Arizona Plateau

The cause of this extraordinary hole is one of the perplexing questions over which scientists speculate. It has been suggested that the crater was caused by impact of a large meteor, a view snstained by the occurrence of many small masses of meteoric iron in the vicinity, but a mining company organized to find and work the large mass of iron presumably buried in the hole obtained no evidence of its existence. A detailed survey with magnetic needle hung to swing vertically also failed to indicate the presence of a body of metallic iron. A plausible suggestion is that the bole was caused by explosion of volcanic steam accumulating in the porous sandstone under the dense limestone and finally reaching the limit of tension. Many conspicuous volcanic features occur in the general neighborhood but not in the immediate vicinity of the hole. Closely similar craters due to explosion are known in the Southwest, in Mexico and other parts of the world.

N. H. Darton,
United States Geological Survey.