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lowering of a portion of the earth's crust. The subsidence of land areas over time has resulted in submergence by shallow seas (see oceansocean,
interconnected mass of saltwater covering 70.78% of the surface of the earth, often called the world ocean. It is subdivided into four (or five) major units that are separated from each other in most cases by the continental masses. See also oceanography.
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). 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 faultsfault,
in geology, fracture in the earth's crust in which the rock on one side of the fracture has measurable movement in relation to the rock on the other side. Faults on other planets and satellites of the solar system also have been recognized.
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. 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 spreadingseafloor spreading,
theory of lithospheric evolution that holds that the ocean floors are spreading outward from vast underwater ridges. First proposed in the early 1960s by the American geologist Harry H.
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) subsides after cooling, as do calderas, the craterlike features at a volcano's peak. An atoll is a coralcoral,
small, sedentary marine animal, related to the sea anemone but characterized by a skeleton of horny or calcareous material. The skeleton itself is also called coral.
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 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. For example, withdrawal of oil from the field at Long Beach, California, beginning in 1936 resulted in subsidence at rates ranging from 0.5 to 2.0 ft (0.15–0.61 m) per yr in the center of the field. By 1962 the center of the oil field had subsided slightly over 27 ft (8.5 m), caused by the removal of fluid from the pore spaces in the underground rock, allowing the grains to compact. Similarly, withdrawal of groundwater through well pumping has resulted in subsidence in such cities as Mexico City, Houston, Tex., and Venice, Italy. Subsidence is also caused by the collapse of underground salt, ore, and coal mines.



the compaction of soil owing to external stress or the soil’s own weight. It occurs in loess and loesslike deposits after artificial wetting and may result from thawing (thermal subsidence in frozen soils) and such dynamic actions as vibration subsidence. The soil’s surface may subside from a fraction of a centimeter to 2 meters. Subsidence may cause cracks on the surface and in the soil mass. If percolation of moisture in soils compacted by wetting occurs after subsidence, deformation of the soil is possible owing to leaching from the soil of water-soluble compounds.

The cause of subsidence in loess and loesslike deposits is insufficient compaction of the soil and accompanying loss of stability in particle bonding as a result of wetting. With soil of a given moisture content, a specific porosity corresponding to each degree of pressure decreases with increasing pressure. The bonds between particles in soil may keep it compact despite an increase in pressure caused by the weight of new deposits or of structures. This gives rise to a disparity between porosity and pressure, or a state of insufficient compaction. Subsidence also results from lowered stability of particle bonding in soil when loess is wetted by leakage from water pipes or when the groundwater level near a reservoir rises. Insufficient compaction of loess and loesslike deposits is characteristic of such arid semi-desert or steppe regions as those in Middle Asia, the Ukraine, the Northern Caucasus, China, Southern Central Europe, and the Mississippi basin. Thermal subsidence may occur in the permafrost zone.

The subsidence properties of loess and loesslike soils are studied in compression testing devices and by wetting trenches. The extent of the compaction of soil when wetted in relation to the original elevation of a soil sample is called the relative degree of subsidence and may vary from 0 to 0.1 or more. Subsidence may arise when the moisture content of soil increases to a certain level (initial moisture content of subsidence) or when pressure exceeds a certain level (initial pressure of subsidence). Conditions for construction on loess and loesslike soils are of two types: surface subsidence of less than 5 cm resulting from the weight of the wet ground itself, and surface subsidence of more than 5 cm. Different conditions require different construction measures.

Steps taken to control subsidence during construction include wetting of the ground, silicification, compaction, and firing. Structural measures are also taken, and the danger of water harming the foundations of structures is eliminated.


Denisov, N. Ia. Stroitel’nye svoistva lessa i lessovidnykh suglinkov, 2nd ed. Moscow, 1953.
Abelev, Iu. M., and M. Iu. Abelev. Osnovy proektirovaniia i stroitel’stva na prosadochnykh makroporistykh gruntakh, 2nd ed. Moscow, 1968.
Gil’man, Ia. D., and V. P. Anan’ev. Stroitel’nye svoistva lessovykh gruntov i proektirovanie osnovanii i fundamentov. Rostov-on-Don, 1971.



A descending motion of air in the atmosphere, usually with the implication that the condition extends over a rather broad area.
(mining engineering)
A sinking down of a part of the earth's crust due to underground excavations.


A sinking of an entire area, in contrast to the settlement of an individual structure.


A descending motion of air in the atmosphere over a broad area, as in polar regions.
References in periodicals archive ?
However, given the tough rhetoric, we expect the regulator to start its easing cycle only after the inflationary pressure starts to subside in Q2 13.
The land naturally sinks, or subsides, as loose sediments from the Mississippi River settle and compact.
Once negotiators decide that TPIs may help to resolve an incident, they must allow strong emotions and tensions to subside before permitting TPIs to enter the process.
From now on, with the referendum discussion behind us, the interest-rate structure will continue to subside, and the value of the Canadian currency should firm as we go forward.
Once the pressures began to subside late in September, the dollar began to drift down toward the levels of late August.
For more information about lactose intolerance, write the clearinghouse.) If your symptoms are severe, your doctor may recommend that you take only liquids or small amounts of soft foods until the symptoms subside. If these measures do not work, your doctor may prescribe medical therapies to control persistent symptoms.
'We hope and pray that the waters would subside so that the process of recovery in the affected areas could immediately begin,' Cayetano added.
"Before, flash floods take around a day in order for it to subside. But on Thursday, it subsided quickly," he said.
Police sources on the ground reported heavy traffic snarl-upon both sides as motorists wait for the rains to subside.
Atmospheric dust levels are expected to get worse this afternoon but subside later in the evening, the meteorological department said on Saturday.
? SUBSIDE has re-opened nearly one year after it was closed to make way for the redevelopment of Birmingham city centre.
What didn't subside for a full six weeks was the tinnitus, which was horrible.