CRATER MOUND (long known as Coon Butte), perhaps the most mysterious geological feature in western United States, is located about I om. S. of Sunshine, Arizona. Viewed from a distance, the mound appears as a low ridge, but on near approach this ridge is found to be circular and to enclose a great hole 4,000ft. in diameter and 600ft. deep. The encircling ridge is from ioo to I5oft. high, and consists of loose fragments of rock and sand, evidently blown out of the hole. The cause of this great hole has not been satisfactorily determined. Several geolo gists believe that it was made by a great meteor, but no evi dences were revealed by the tests made. Others suggest that it is due to an explosion of steam from volcanic sources below. The latter theory would account for the somewhat upturned and broken strata of the rim.