UPDATE: Location Revealed
Step Mountain is a Tertiary-aged (dated at 36 million years) andesitic dike in Rose Canyon, three miles southwest of Herriman. The summit is at 6109 feet above sea level. The mountain is a fine example of columnar jointing, typically associated with basalt, but also found in andesites. Columnar jointing is found below the surface of thick lava flows, sills, and dikes, and is caused by the cooling and contracting of the lava creating long vertical joints that form slender polygonal columns, typically pentagonal or hexagonal in shape. In the case of Step Mountain dike, magma filled a crack in the pre-existing rock and the joints formed horizontal to the surface, so the columns act as “steps.” The weathering-resistant dike now has a prominent relief due to the erosion of the softer surrounding volcanic rock.