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Geology of Nevada Jonathan G. Price Preprint from Castor, S.B., Papke, K.G., and Meeuwig, R.O., eds., 2004, Betting on Industrial Minerals, Proceedings of the 39th Forum on the Geology of Industrial Minerals, May 19–21, 2003, Sparks, Nevada: Nevada Bureau of Mines and Geology Special Publication 33. Abstract The geology of Nevada is the foundation of its natural Geology plays a central role in Nevada’s human history, resources and is closely linked to its human history. The economy, and future. Cordilleran tectonics have created the Basin complex geologic history of the state relates to such and Range landscape and interior drainage of the Great Basin, provided a rain shadow to make Nevada the nation’s driest state, resources as minerals, water, and energy; to environmental and generated frequent earthquakes along normal and strike-slip issues; and to natural hazards. This article draws heavily faults. Geology is key to reducing risks from Nevada’s natural and from the references listed in the bibliography for general anthropogenic hazards (earthquakes, flash floods, drought, land information on the geology of the state, particularly subsidence, erosion after wildland fires, landslides, swelling and Stewart (1980), Stewart and Carlson (1978), Price and collapsing soils, radon, arsenic, and others). others (1999), and Price (2002). Nevada’s geologic fortunes make it the leading state in the production of gold, silver, barite, lithium, and mercury and a major Mountain ranges in Nevada, commonly about 10 producer of geothermal power and gypsum. The metals are primarily miles wide and rarely longer than 80 miles, are separated related to igneous activity, with major pulses of magma during the by valleys. The geologic structure that controls this basin- Jurassic, Cretaceous, and Tertiary. Barite is mined from Paleozoic and-range topography is dominated by faults. Nearly sedimentary rocks, and gypsum occurs in sedimentary beds of every mountain range is bounded on at least one side by Permian, Triassic, Jurassic, and Tertiary age. Lithium is extracted from brine beneath an unusual playa. Geothermal power production a fault that has been active, with large earthquakes, during primarily occurs along Quaternary faults. the last 1.6 million years. For the last several million years, We are in the midst of the biggest gold-mining boom in these faults have raised and occasionally tilted the American history. The Carlin trend is one of the world’s premier mountains and lowered the basins. Over the years, these gold-mining regions, and reserves along the trend and elsewhere basins have filled with sediments that are derived from in Nevada will sustain the boom for at least two more decades. Nevada’s booming population will continue to increase demands Figure 1. The Carson Range, with Lake Tahoe in the background, for construction raw materials and for geological information to near Genoa and Walley’s Hot Springs, Douglas County; photo help manage growth while minimizing losses from geological by Terri Garside. A prominent fault scarp occurs at the base of hazards. the range. 1 erosion of the mountains and that are locally tens of most of Nevada transforms into northwest-trending ranges thousands of feet thick. within the Walker Lane. Many of the range-bounding faults are still active The climate of Nevada is closely tied to the geologic (Figs. 1 and 2). Nevada is the third most seismically active structure and resultant topography. Judging from fossil state in the nation (behind California and Alaska); over evidence of plants that grew in different parts of California the last 150 years, a magnitude 7 or greater earthquake and Nevada in the past, the Sierra Nevada (in California has occurred somewhere in Nevada about once every 30 and far western Nevada) rose to current elevations only years. Most faults are normal, although some are strike- within the last six million years. Today the Sierra Nevada slip faults. The most apparent zone of strike-slip faults in and other high mountains in California trap moisture Nevada is in a 50-mile wide swath along the northwest- coming off the Pacific Ocean and leave Nevada the driest trending border with California, the Walker Lane. These state in the nation. Only a few rivers leave Nevada. These northwest-trending faults are accommodating part of the include the Bruneau, Jarbidge, and Owyhee Rivers in motion between the Pacific Plate, which is moving northeastern Nevada, which flow north into the Snake relatively northwest, and the North American Plate, which River in Idaho, and the White and Virgin Rivers in is moving relatively southeast. The San Andreas Fault southeastern Nevada, which flow into the Colorado River takes up most of the motion between these two plates. (Fig. 3). The Colorado, which is the largest river in The generally north-south trend of mountain ranges in Nevada, gets the bulk of its water from the Rocky Mountains to the east and provides much of the municipal and industrial water for Las Vegas and other communities in southern Nevada before flowing southward into the Gulf of California. Most of Nevada, however, is part of the Great Basin, a large area with no drainage to the ocean and centered on Nevada but including parts of California, Oregon, Idaho, and Utah. The Truckee, Carson, and Walker Rivers, which provide much of the drinking, industrial, and agricultural water for northwestern Nevada, flow generally eastward from the Sierra Nevada to terminal lakes and lowlands in the desert (Pyramid Lake, the Carson Sink, and Walker Lake, respectively). The Humboldt River, which supplies much of northeastern Nevada with drinking, agricultural, and industrial water, flows southwestward into Humboldt Lake, and, when the lake fills, into the Carson Sink. During glacial times (most recently about 10,000 years ago), large expanses in the Great Basin were covered by water. Great Salt Lake and the Bonneville Salt Flats in Utah and parts of far eastern Nevada were once part of ancient Lake Bonneville, and Pyramid Lake, the Carson Sink, and Walker Lake were once connected in ancient Lake Lahontan. Native Americans occupied the shores of these lakes as early as 10,000 to 12,000 years ago. Glaciers existed in the higher mountains, carving some of the spectacular U-shaped valleys in the Ruby Mountains (Fig. 4) and sculpting high-mountain topography in the Sierra Nevada. Glaciers are still present high in the Ruby Mountains and Snake Range in eastern Nevada. Groundwater, mostly from aquifers in alluvial basins, Figure 2. Backhoe trench along the Genoa fault near Walley’s Hot Springs, south of the town of Genoa, Douglas County. The is used throughout the state. In some basins, groundwater maximum displacement along the fault during its last event, about has been pumped out more rapidly than it is naturally 550 to 650 years ago, was 18 feet (Ramelli and others, 1999). recharged from rain and snowmelt; this causes significant See www.nbmg.unr.edu/dox/sp27.pdf for Nevada Bureau of lowering of the groundwater table and can affect the land Mines and Geology Special Publication 27, a booklet on Living with Earthquakes in Nevada, for more information about surface. In Las Vegas Valley, cracks have developed earthquake hazards. locally in the ground (near preexisting faults), and in a 2 ° ° 120 ° ° ° 115° 114 42° 119 118 117° 116 42° J J a E a r r . S O b b F . i i d w B o F d g y r r o g k h u e r e n e k e e R R a . O R . w i u yh v e e r R e i v R e i r v e r boldt R m iv u e H r k r o F . N 41° 41° Winnemucca H u m b ol Elko dt River Carlin Battle Mountain Y E L Pyramid L A Lake Lovelock V E PIN 40° 40° CARSON SINK Reno r e Rive cke Eureka ru Austin T Fallon Virginia City Ely rson River Ca W Carson alk City er ° R 39 Yerington iv 39° e 120° Minden r E Gabbs . W lker a a l W k Walker e . r Y W R Lake . E L L Hawthorne A V D A O R IL A 119° R W h ite R iv Tonopah e r 38° 38° Pioche Silver Peak Goldfield 118° 0 10 20 30 40 50 miles P a h r a 0204060 80 kilometers n a g a t 37° County boundaries 37° W a s h Beatty Yucca ° r 117 Mountain ve M Ri ud d in y g r R i . V Las Vegas Lake 116° Mead 36° 36° C o l o r a d Figure 3. Shaded relief map of Nevada (modified from Nevada o R i v Bureau of Mines and Geology Educational Series E-31). See e r www.nbmg.unr.edu for this and other free maps, including E-30, a generalized geologic map of Nevada. 115° 3 Figure 4. Hanging valley, carved by glaciers, that is a tributary of Lamoille Canyon, Elko County. few places the land has subsided more than 6 feet in the last 60 years (Fig. 5). On a percentage basis, Nevada is the fastest growing state in the country. The U.S. Census Bureau reported a population of 1,201,833 in 1990 and 1,998,257 in 2000. Most of the increase has occurred in and around the urban areas of Las Vegas and Reno-Carson City. Urban expansion in the Las Vegas area has been at a rate of about two acres per hour and is expected to continue at a rapid rate. The Nevada State Demographer has projected the population to be 2.8 million in 2010 (Fig.