Salt Domes

Introduction
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.

Salt domes, NASA

Domes of salt visible from space, NASA

Diapirs
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 surrounding 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.

Table salt
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.

Oil deposits
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.

More Rock Cycle Links

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Pahoehoe-Lava Find out how pahoehoe lava forms in the Hawaiian Islands.


Pyroclastic Rocks Find out how pyroclastic rocks form during volcanic eruptions.

Salt Domes Learn more about how domes form, what they are used for and how they are sometimes a key to find oil.

Rock Cycle Learn more about igneous, sedimentary and metamorphic rocks and how they form.

Kids Fun Science The links on our home page include information about volcanoes, science activities, plate tectonics, the rock cycle and much more.

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