This earthcache attempts to show a regional feature that stretches across many states. This would best be done from the air or with hundreds of miles of driving, so please keep that in mind when visiting this earthcache.
Antelope Island sits at the eastern edge of the Basin and Range province. A geologic province is a region with similar geologic features and processes. The Basin and Range province is characterized by steep roughly parallel linear mountain ranges with deep basins separating them. These basins have typically filled with sediment to form flat deserts. The Basin and Range province extends from eastern California to central Utah, and from Southern Idaho to Sonora Mexico.
The Basin and Range province is the result of the stretching and thinning of the earth’s crust that began about 20 million years ago. Since then, the region has been stretched by as much as 100% of its original width and appears to be continuing today at the rate of about 1 cm/year.
Image source: Extent of Basin and Range, Answers.com Image source: Shaded Digital Elevation Model Data of Nevada, NASA
This stretching has pulled the California and Baja California away from the center of the continent. As the crust pulled apart, roughly north-south normal faults formed to accommodate the extension. In a normal fault, the rock on one side of the fault slides down the fault plane. In addition to one side sliding down relative to the other, it also moves two points on the surface away from each other creating the extension.
Valleys formed in the down-dropped sides leaving the high mountain ranges. These mountain ranges eroded into the valleys filling them with sediment. Due to the thinning and faulting of the earth’s crust this region also has relatively common volcanism.
Image Source: Normal fault, USGS
The coordinates are on one of the ranges, Antelope Island and you can see the ranges to the east, the Wasatch Range, and west, Carrigton and Stansbury Island. Beyond these islands to the west are the Lakeside and Cedar Mountains. Both to the east and west the Great Salt Lake has filled in the basins between these ranges. (This might better be seen from the top of Frary Peak, but that location is a challenge to hike up to. There are also a few National Parks where features of the Basin and Range can be observed http://wrgis.wr.usgs.gov/docs/parks/province/basi.html.)
The Basin and Range extension has also created another large geomorphological feature, The Great Basin. The Great Basin is an internal drainage, none of the surface water drains to the ocean. This region includes a 200,000 square mile area that includes Nevada, most of Utah, and portions of Idaho, California, and Oregon. It is shown in orange on the adjacent map. On the NASA shaded digital elevation model the Great Basin is outlined in light green.
Image: Great Basin outline, USGS http://pubs.usgs.gov/of/1999/of99-425/webmaps/home.html
This region is not one single watershed but instead a number of individual watersheds that drain to separate basins. Any precipitation that falls in this region usually collects in one of many short-lived lakes called playas and quickly evaporates or percolates into the ground to become groundwater.
However, enough water and snow melt drain to the Great Salt Lake to make it a permanent lake. On the average, the amount of water that drains into the lake from the surrounding mountains during the spring evaporates later in the summer. There are yearly fluctuations that cause yearly changes in the lake level (See Oolites of the Great Salt Lake Earthcache)
Send me a note with :
- The text "GCZ5ZC Basin and Range Province and Great Basin" on the first line
- The number of people in your group.
- There are a few other island and peaks in and around the Great Salt Lake. Send me a note explaining if these other islands are part of the Basin and Range expansion or if they are volcanic.
The above information was compiled from the following sources:
- USGS, Geologic Provinces of the United States: Basin and Range Province, http://wrgis.wr.usgs.gov/docs/parks/province/basinrange.html
- USGS, A Tapestry of Time and Terrain: The Union of Two Maps – Geology and Topography, The Basin and Range Province, http://tapestry.usgs.gov/features/22basinrange.html
- Willis, Grant C. et al, Geology of Antelope Island State Park, Utah in Geology of Utah’s Parks and Monuments, 2003 Utah Geological Association Publication 28 (second edition)
- D.A. Sprinkel, T.C. Chidsey, Jr. and P.B. Anderson, editors Flight Across the United States – Boston to Denver to San Francisco, The Nevada Basin and Range; The Desert Southwest; and The Snake River Plains, NASA, http://rst.gsfc.nasa.gov/Sect6/Sect6_8.html
- USGS, Visual Glossary, Fault, Normal faults, Reverse faults, Strike-slip fault, Fault scarp, http://wrgis.wr.usgs.gov/docs/parks/deform/gfaults.html
- USGS, Open-file Report 99-425 online version1.0, Geothermal Industry Temperature Profiles from the Great Basin, http://pubs.usgs.gov/of/1999/of99-425/webmaps/home.html