Image:Gwsanjoaquin.jpg
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[edit] Summary
USGS picture found at [1] Approximate location of maximum subsidence in the United States identified by research efforts of Dr. Joseph F. Poland (pictured). Signs on pole show approximate altitude of land surface in 1925, 1955, and 1977. The site is in the San Joaquin Valley southwest of Mendota, California.
The compaction of unconsolidated aquifer systems that can accompany excessive ground-water pumping is by far the single largest cause of subsidence. The overdraft of such aquifer systems has resulted in permanent subsidence and related ground failures. In aquifer systems that include semiconsolidated silt and clay layers (aquitards) of sufficient aggregate thickness, long-term ground-water-level declines can result in a vast one-time release of “water of compaction” from compacting aquitards, which manifests itself as land subsidence (fig. 2).
[edit] Licensing
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This work is in the public domain in the United States because it is a work of the United States Federal Government under the terms of Title 17, Chapter 1, Section 105 of the US Code. See Copyright. Note: This only applies to works of the Federal Government and not to the work of any individual U.S. state, territory, commonwealth, county, municipality, or any other subdivision. |
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File history
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| Date/Time | Dimensions | User | Comment | |
|---|---|---|---|---|
| current | 13:49, 19 February 2007 | 228×494 (24 KB) | Zeizmic (Talk | contribs) | (USGS picture found at [http://water.usgs.gov/ogw/pubs/fs00165/]) |
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