Salt domes are associated with oil and gas deposits in the Gulf of Mexico. They are increasingly used as impervious storage areas for dangerous chemicals. Some spent nuclear waste has been stored in these domes.
Domes of salt visible from space, NASA
Diapirs are rock formations that develop when ancient seas evaporate leaving behind thick layers of salt deposits. Over time the salt deposits are covered with deep layers of sediment carried into the basins by river water. The salt eventually turns into solid rock that is lighter than the surrounding rock.
Diapirs moving upward
The salt is less dense than the country rock and begins to "bubble" upward breaking through weak spots in the sedimentary rocks. Salt domes are called diapirs, which comes from a Greek word meaning to pierce.
Salt in a diapir is sometimes mined for table salt or used on roads to melt ice in the winter. The domes are also used as storage areas because they are almost impermeable.
The salt pushing upward forms pockets between the shale rocks and the domes. Oil and gas often collects in these pockets. Oil companies drill into the pockets to obtain the petroleum used to make gasoline. A major source of the oil found in the Gulf of Mexico is in the pockets associated with salt diapirs.
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