[The “Wagonwheel”, an unusual circular pattern of canals just south of Yellow Cotton Bay, also owes its pattern to the combination of geology and extractive logistics.  Here, the oil companies’ canals depart from their typically linear vocabulary to follow the roughly circular limit of a raised salt dome.  Salt domes form when buried deposits of rock salt, which typically has a lower density than the surrounding materials, slowly rise through sedimentary material, thrusting upward towards the surface.  (The study of the “geometries and processes” associated with the movement of salt through the earth is known as “salt tectonics”.)  As they do so, the strata they crunch through tend to bend upward at the edges of the forming salt domes, producing pockets where hydrocarbons — like petroleum and natural gas — can collect.  Those filled pockets attract the extractors, and the extractors produce patterns like the Wagonwheel.   These salt domes are not uncommon in the delta region: Avery Island, for instance, is another example (and also a site of extraction.)]