Case Study: Land Subsistence in the American Southwest

A) The greatest cause of land subsidence is over drafting aquifer. This occurs when ground water is pumped from areas with clay/silt beds around it. These beds lose support due to loss of water pressure. As the water is gradually drained from the clay/silt, the beds are compressed and the land is permanently lowered and compacted. Other Causes include human activity such as the underground pumping of resources (water, oil and gas),sinkholes,soil drainage, and mine collapse.

As human development increases, more and more resources are taken from the earth. The more resources that are taken from the earth, the more he earth is damaged. 

B)Land subsidence can be hazardous to construction and development. It can cause damage to buildings and infrastructure as well as pipelines, sewage, and drainage systems. Transportation is effaced as bridges,roads, railroads, can be ruined. Well casing failure is also an issue. Furthermore, as the land lowers in coastal areas, the tide may advance to areas which were never before below tide level. Earth fissures(cracks/openings in the earth) may also occur as a result of land subsidence.

C)  Some ways to prevent land subsidence would include drafting aquifers where there are less clay and silt beds. Soil drainage can be minimized and underground pumping can be more spread out and gradual causing a weaker impact on the soil. Mines can be more strongly reinforced and filled in before use so as not to accidentally collapse and lead to subsistence.