Geological profile through northern Germany with salt domes (blue)

Astronaut photography of salt domes in the Zagros Mountains (the white area in the middle and the hill on the left)

A salt dome is a type of structural dome formed when a thick bed of evaporite minerals (mainly salt, or halite) found at depth intrudes vertically into surrounding rock strata, forming a diapir. The Zagros Mountains (جبال زاجروس (رشته كوههاى زاگرس ( Sorani Kurdish: Zagros - زاگرۆس make up Iran 's and Iraq 's In Geology, a dome is a deformational feature consisting of symmetrically-dipping Anticlines their general outline on a geologic Map is circular or oval Evaporites (iˈvæpəraɪt are water-soluble Mineral sediments that result from the Evaporation of bodies of surficial Water. Halite is the Mineral form of Sodium chloride, Na[[chlorine Cl]] commonly known as rock salt. In Geology and related fields a stratum (plural strata) is a layer of rock or Soil with internally consistent characteristics that distinguishes A diapir (ˈdaɪəpɪər) ( French, from Greek diapeirein, to pierce through is an Intrusion caused by Buoyancy and Pressure

The salt that forms these domes was deposited within restricted marine basins. Due to restricted flow of water into a basin, evaporation occurs resulting in the precipitation of salts from solution, depositing evaporites. It is recognised that a single evaporation event is rarely enough to produce the vast quantities of salt found in evaporite deposits indicating that a sustained period of episodic flooding and evaportation of the basin must occur, as can be seen from the example of the Mediterranean Messinian salinity crisis. The Messinian Salinity Crisis, also referred to as the Messinian Event, is a period when the Mediterranean Sea evaporated partly or completely dry during the At the present day, evaporite deposits can be seen accumulating in basins that merely have restricted access but do not completely dry out; they provide an analogue to some deposits recognised in the Geological record, such as the Garabogazköl basin in Turkmenistan. The Garabogazköl, alternatively the Kara-Bogaz-Gol (literally "mighty strait lake" is a shallow inundated depression in the northwestern corner of Turkmenistan Turkmenistan ( Türkmenistan; also known as Turkmenia) is a Turkic country in Central Asia.

Over time, the salt is covered with sediment and becomes buried. Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of Since the density of salt is generally less than that of surrounding material, it has a tendency to move upward toward the surface, forming large bulbous domes, diapirs , sheets, pillars and other structures as it rises. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different A diapir (ˈdaɪəpɪər) ( French, from Greek diapeirein, to pierce through is an Intrusion caused by Buoyancy and Pressure If the rising salt diapir breaches the surface, it can become a flowing salt glacier. A salt glacier is a flow of Salt (typically Halite) that is created when a rising Diapir in a Salt dome breaches the surface much like In cross section, these large domes may be anywhere from 1 to 10 kilometers across and extend as far down as 6. 5 kilometers.

One example of an island formed by a salt dome is Avery Island in Louisiana. An island (ˈaɪlənd or isle (/ˈaɪl/ is any piece of land that is completely surrounded by water in two dimensions above high tide and isolated from other significant Salt is a Dietary mineral composed primarily of Sodium chloride that is essential for Animal life but toxic to most land plants A dome is a common structural element of Architecture that resembles the hollow upper half of a Sphere. Avery Island is a Salt dome located in Iberia Parish Louisiana, United States, about three miles (5 km inland from Vermilion Bay, which in The State of Louisiana ( or, État de Louisiane, pronounced) is a state located in the southern region of the United States of America At present ocean levels it is no longer surrounded by the sea but it is surrounded by bayous on all sides. A bayou (pronounced oʊ or uː is a small slow-moving Stream or creek or a lake or pool ( bayou lake) that lies in an abandoned channel of a stream

Another example of an emergent salt dome is at Onion Creek / Fisher Towers near Moab, UT, U. Onion Creek is a Census-designated place (CDP in Travis County, Texas, United States. S. These two images show a Cretaceous age salt body that has risen as a ridge through several hundred meters of overburden, predominately sandstone. As the salt body rose, the overburden formed an anticline (arching upward along its centerline) which fractured and eroded to expose the salt body.

End-on view of emergent salt dome between remnants of displaced overburden

Lateral view of emergent salt dome from ridge of remnant of displaced overburden

The term "salt dome" is also sometimes inaccurately used to refer to dome-shaped silos used to store rock salt for melting snow on highways. Halite is the Mineral form of Sodium chloride, Na[[chlorine Cl]] commonly known as rock salt. These domes are actually called monolithic domes and are used to store a variety of bulk goods. A monolithic dome (from Greek mono- and -lithic meaning "one stone" is a structure cast in one piece over a form usually of Concrete or similar structural material

Commercial uses

The rock salt that is found in salt domes is mostly impermeable. As the salt moves up towards the surface, it can penetrate and/or bend strata of existing rock with it. As these strata are penetrated, they are generally bent slightly upwards at the point of contact with the dome, and can form pockets where petroleum and natural gas can collect between impermeable strata of rock and the salt. Petroleum ( L petroleum, from Greek πετρέλαιον, lit Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane, The strata immediately above the dome that are not penetrated are pushed upward, creating a dome-like reservoir above the salt where petroleum can also gather. These oil pools can eventually be extracted, and indeed form a major source of the petroleum produced along the coast of the Gulf of Mexico. The Gulf of Mexico ( Spanish: Golfo de México) is the ninth largest Body of water in the world

Other uses include storing oil, gas, or even hazardous waste in large caverns formed after salt mining, as well as excavating the domes themselves for uses in everything from table salt to the granular material used to prevent roadways from icing over. This article refers to the United States Strategic Petroleum Reserve The Waste Isolation Pilot Plant, or WIPP, is the world's second underground repository (after closure of the Germany 's Asse Salt Mine in A cave is a natural underground void large enough for a human to enter For sodium chloride in the diet see Salt. Sodium chloride, also known as common salt, table salt, or Halite, is a

See also

• Salt tectonics
• Strategic Petroleum Reserve

External links

• Salt dome at Schlumberger's Oilfield Glossary
• Hattiesburg Mississippi Salt Domes interactive map of domes use to store LPG and other gas