Subsidence

Human Depedence Project

This Is Subsidence

subsidence, lowering of a portion of the earth's crust. The subsidence of land areas over time has resulted in submergence by shallow seas (see oceans). Land subsidence can occur naturally or through human activity. Natural subsidence may occur when limestone, which is easily carved by underground water, collapses, leaving sink holes on the surface, such as in Florida. Earthquakes can also cause subsidence of the land because of the movement of faults. Permafrost, or the permanently frozen ground in tundra regions, can subside during local warming trends, a phenomena called thermokarst. Oceanic crust produced at spreading ridges (see seafloor spreading) subsides after cooling, as do calderas, the craterlike features at a volcano's peak. An atoll is a coral reef that forms a ring with no apparent central peak and may form when volcanic islands subside—an explanation first proposed by Charles Darwin. Human activity has contributed greatly to subsidence over the last few centuries. http://www.encyclopedia.com/topic/subsidence.aspx

2 Main Issues Of Subsidence

Subsidence frequently causes major problems in karst terrains, where dissolution of limestone by fluid flow in the subsurface causes the creation of voids.Several types of sub-surface mining, and specifically methods which intentionally cause the extracted void to collapse (such as pillar extraction, longwall mining and any metalliferous mining method which uses "caving" such as "block caving" or "sub-level caving") will result in surface subsidence.

The Neggative Effects On The Enviorment

Subsidence is a global problem, and the increasing of land and water resources threatens to exacerbate existing land-subsidence problems and initiate new ones.


http://water.usgs.gov/edu/earthgwlandsubside.html

Main Regions in or nearest to North America affected by Subsidence

Mexico City, where long-term extraction of groundwater has caused significant land subsidence and associated aquifer-system compaction, which has damaged colonial-era buildings, buckled highways, and disrupted water supply and waste-water drainage. Land subsidence in California, due to groundwater withdrawal. Fissures near Lucerne Lake (dry) in San Bernardino County, Mojave Desert, California.

http://water.usgs.gov/edu/earthgwlandsubside.html

Land subsidence, a growing problem

What Wildlife is most affected by Subsidence

Groundwater is a valuable resource both in the United States and throughout the world. Where surface water, such as lakes and rivers, are scarce or inaccessible, groundwater supplies many of the hydrologic needs of people everywhere.

http://water.usgs.gov/edu/gwdepletion.html

How are Wildlife affected by Subsidence

Longwall mining is an underground coal mining technique which involves removing a portion of an underground coal seam. Longwall mining can cause the land above the mined-out coal seam to destabilise and collapse - this is known as subsidence.

http://www.environment.nsw.gov.au/threatenedspecies/LongwallMining.htm

Does Subsidence affect our lives in in League City?

The greater Houston area, possibly more than any other metropolitan area in the United States, has been adversely affected by land subsidence. Extensive subsidence, caused mainly by ground-water pumping but also by oil and gas extraction, has increased the frequency of flooding, caused extensive damage to industrial and transportation infrastructure, motivated major in- vestments in levees, reservoirs, and surface-water distribution facili- ties, and caused substantial loss of wetland habitat. http://pubs.usgs.gov/circ/circ1182/pdf/07Houston.pdf

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Are people affected by Subsidence?

Even relatively modest subsidence can also damage a variety of human structures. Buildings are weakened and collapse, railway lines and roads are twisted and broken, and underground sewer, power, and water lines are torn apart. Due to its ability to destroy property on a large scale, subsidence is a very expensive type of mass wasting that also poses some risk to human lives.
http://science.jrank.org/pages/6565/Subsidence-Effects-subsidence.html

Who or What causes Subcidence to occur?

Land subsidence occurs when large amounts of groundwater have been withdrawn from certain types of rocks, such as fine-grained sediments. The rock compacts because the water is partly responsible for holding the ground up. When the water is withdrawn, the rocks falls in on itself. You may not notice land subsidence too much because it can occur over large areas rather than in a small spot, like a sinkhole.

http://water.usgs.gov/edu/earthgwlandsubside.html

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What solutions that people have come up with for Subsidence?

Settlement usually occurs in new or relatively new buildings. They are very heavy and cause the ground to compact, but this normally stops after a short while. Additionally, most buildings are constructed in a variety of materials, all of which need to settle down and have different shrinkage rates. It is not unusual for a builder’s contract to require them to come back in six months to make good those settlement cracks that have appeared, for instance, between the walls and ceilings. http://www.telegraph.co.uk/finance/property/advice/propertyclinic/7251914/Subsidence-what-you-need-to-know.html

New idea for a new solution

They could help everyone remake homes, help people out who are suffering. Other states or countries around the world could give donations of food or water and shelter, for people who lost there homes.
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