Tabbys Peak in the Cedar Mountains, Tooele County, Utah.
Photographer: Don Clark
About 40 million years ago, magma intruded to form a large dike. While cooling, the magma shrank and fractured into a six-sided column pattern, resulting in the blocky appearance of the weathered andesite at Tabbys Peak in the Cedar Mountains, Tooele County.
The Utah Geological Survey (UGS) is a division of the Utah Department of Natural Resources. Several specialized programs comprise the UGS: Data Management, Energy & Minerals, Geologic Hazards, Geologic Information & Outreach, Geologic Mapping, Groundwater & Wetlands, and Paleontology.
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