Geology of Glen Canyon National Recreation Area, Arizona and Utah

The park

Glen Canyon National Recreation Area, established October 27, 1972, lies at the heart of the Colorado Plateau, from the Orange Cliffs in Utah to Lees Ferry in northernmost Arizona. It covers about 507,523 hectares (1,254,117 acres) of rugged canyon country in Garfield, Kane, San Juan and Wayne counties, Utah, and Coconino County, Arizona.

• Lake Powell stretches about 300 km (186 miles) behind Glen Canyon Dam, with 3,150 km (1,960 miles) of shoreline and 96 major side canyons.
• The area also takes in stretches of the Colorado and San Juan rivers, and borders Canyonlands, Capitol Reef, Grand Canyon and Rainbow Bridge.
• People have lived in and explored Glen Canyon for more than 10,000 years.

Three hundred million years of rock

More than 3,000 m (10,000 feet) of sedimentary rock span the Pennsylvanian, the Permian and the whole Mesozoic — about 300 million years. They record:

• several mountain-building events;
• the assembly of the supercontinent Pangea;
• repeated invasions of shallow seas;
• vast deserts of Sahara-like dunes;
• the age of dinosaurs;
• unusual igneous intrusions called laccoliths;
• the carving of the Colorado River system.

The Mesozoic exposures, from about 252 million to 66 million years ago, are among the best Mesozoic sequences in the national parks, documenting ancient ecosystems and climates.

Slickrock sandstone with desert varnish and cross-bedding. NPS photo by Bob Moffit.

Landforms

Glen Canyon's landforms include mesas, buttes, cliffs, slickrock, slot canyons, alcoves, hanging gardens, arches, natural bridges, badlands, hoodoos, entrenched meanders, desert varnish, sandstone pipes and weathering pits.

Protected resources

• Fossils are protected under the Paleontological Resources Preservation Act of 2009.
• Caves are protected under the Federal Cave Resources Protection Act of 1988.
• Abandoned mine lands can be valuable cultural sites and habitat, but many are dangerous and pollute water and land. Near them: stay out and stay alive.

Setting and inventories

Glen Canyon belongs to the Colorado Plateaus Physiographic Province.

Geologic map of Glen Canyon National Recreation Area. NPS Geologic Resources Inventory.

The NPS Geologic Resources Inventory has produced digital maps, a report (Graham, 2016) and posters for the park (DataStore), and a soil inventory is complete (DataStore). More: Glen Canyon geology and fossils, the Arizona Geological Survey and the Utah Geological Survey.

Sources

Based on "NPS Geodiversity Atlas—Glen Canyon National Recreation Area, Arizona and Utah," National Park Service; a work of the United States government in the public domain.