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Salt domes come from layers of salt. Salt layers were deposited in the same manner as the salt layers are currently being deposited in The Dead Sea or The Great Salt Lake. When large bodies of water are isolated from the oceans and the water in these large lakes evaporates, the precipitated salt and gypsum layers are left as lake bed deposits. These precipitates, called evaporites, only make up a small portion of sedimentary record, and yet their movement or flow can have a significant impact on subsurface geology and hydrocarbon accumulation.
The process of creating the giant salt domes underneath the Katy Prairie and elsewhere around the earth starts when Sodium (Na), Potassium (K), Magnesium (Mg), Chloride (Cl), and other ions are extracted from rocks and sediments during chemical erosion processes. These ions are carried by streams and rivers to lakes and oceans. In the process these ions combine and precipitate to create salts like Sodium-Chloride (NaCL), Potassium Chloride (Kcl), and Magnesium Chloride (MgCl). In the Dead Sea, these salt layers grow at a very fast rate of 20 millimeters per year.3.140 This translates to 20 meters (~70 feet) per millennium (1,000 years) of salt being added to the bottom of the Dead Sea, which, again, is considered a very fast rate for chemical deposition. Salt layers around the earth are often hundreds of feet thick, and cover gigantic areas.
The salt dome creation process continues when these salt layers become buried in the geologic record. Rivers, like the Mississippi River, bring eroded sediments from the mountains and the plains. These eroded sediments cover whatever is at the mouth of the river, including the salt layers, as shown in Figure 9. Over geologic time the sands and shales, and the carbonates from reef building are very thick (thousands of feet thick) compared to the thin evaporite layers (hundreds of feet thick).
Under the pressure of overlying sediments, the salts act like a liquid and flows. Faults and areas with less sedimentary overburden provide a place for the salt to move to. The movement of the salt is like the movement of toothpaste inside a toothpaste container. As the salt is squeezed out of areas it leaves what is referred to as a salt weld. The places the salt moves to are referred to become salt pillows or salt domes, which grow over geologic time to be these giant subsurface mountains shown in Figures 44 and 45.
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paradoxes
