Thousands of barrels with bizarre “white halos” were found deep beneath the U.S. coast near Los Angeles, and scientists are starting to unravel the mystery. A study published Tuesday in the journal PNAS Nexus shows they contain a caustic alkali waste, resulting in the sea floor halos and a concrete-like crust inside the circles. Caustic means it can corrode materials it comes into contact with, and alkali is a substance that reacts with water. When the waste leaked from the barrels, it reacted with the water to form brucite, creating the concrete-like sediment. And as that sediment dissolves, it becomes odd-looking halos around each barrel. The barrels were initially discovered in 2021 in the San Pedro Basin. Researchers were concerned they could possibly contain a pesticide called DDT, wh

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