Utah Geological Survey

POTD October 14, 2013: St. George basin, Washington County, Utah

St. George basin, Washington County, Utah
Photographer: Robert F. Biek

Ruins of the Harrisburg town site, established by Mormon pioneers in 1861, consist of blocks of Early Jurassic-age Springdale Sandstone, which a mile to the north is the main ore-bearing horizon of the Silver Reef mining district. The mining district is famous among geologists for its uncommon occurrence of silver ore in sandstone. In the distance, the Pine Valley Mountains tower 7,000 feet above the surrounding red-rock country.

Utah Geological Survey

POTD October 11, 2013: Little Cottonwood Canyon, Salt Lake County, Utah

Little Cottonwood Canyon, Salt Lake County, Utah
Photographer: Taylor Boden

Igneous (gray) and metasedimentary (brown) rocks in Little Cottonwood Canyon, Salt Lake County, Utah.

Utah Geological Survey

POTD October 10, 2013: Mineral Basin, Utah County, Utah

Mineral Basin, Utah County, Utah
Photographer: Grant Willis

Tilted Paleozoic strata in the “Bookends” area  of Mineral Basin, Utah County, Utah.

Utah Geological Survey

POTD October 9, 2013: Little Cottonwood Canyon, Salt Lake County, Utah.

Little Cottonwood Canyon, Salt Lake County, Utah.
Photographer: Stefan Kirby

Pfiefferhorn Peak, a glacier-carved “horn” above Little Cottonwood Canyon, Salt Lake County, Utah

Utah Geological Survey

POTD October 8, 2013: Wasatch Range, Salt Lake County, Utah

Wasatch Range, Salt Lake County, Utah.
Photographer: Stefan Kirby

A winter storm clears from Superior Peak (11,132 feet) in upper Little Cottonwood Canyon southeast of Salt Lake City. Beneath its thick blanket of snow, Superior Peak is made up of tilted Precambrian-age sedimentary rocks, including the Big Cottonwood Formation and overlying Mineral Fork Tillite.

Utah Geological Survey

POTD October 7, 2013: Pine Park, Dixie National Forest, Washington County, Utah.

Pine Park, Dixie National Forest, Washington County, Utah.
Photographer: Tyler Knudsen

Stone domes and minarets in relatively soft volcanic tuff shaped by wind and water.

Utah Geological Survey

POTD October 4, 2013: Lost Canyon, Needles District, Canyonlands National Park, San Juan County, Utah.

Lost Canyon, Needles District, Canyonlands
National Park, San Juan County, Utah.
Photographer: Robert Blackett

Backpackers traverse a “slick rock” rim of the Permianage Cedar Mesa Sandstone.

Utah Geological Survey

POTD October 3, 2013: Maple Canyon, eastern San Pitch Mountains, Sanpete County, Utah.

Maple Canyon, eastern San Pitch Mountains, Sanpete County, Utah.
Photographer: Don Clark

Cretaceous-age conglomerate deposited during a mountain-building episode 75 million years ago.

Utah Geological Survey

POTD October 2, 2013: Capitol Reef National Park, Wayne County, Utah

Capitol Reef National Park, Wayne County, Utah
Photographer: Tyler Knudsen

Juniper-covered siltstone ledges of the Torrey Member of the Triassic-age Moenkopi Formation (foreground) rise to a seemingly impenetrable wall of Triassic- to Jurassic- age Wingate (red vertical cliffs in middle of photo) and Navajo (white bluffs at top of cliff) Sandstones in Capitol Reef National Park.  Early explorers referred to any long barrier to travel as a “reef,” while the dome-shaped bluffs of Navajo Sandstone reminded them of the United States Capitol building—thus the name “Capitol Reef.”

Utah Geological Survey

POTD October 1, 2013: Cedar Mountains, Tooele County, Utah

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.