Santa Barbara oil spill - 1969

Though federal standards at the time required such sites to be outfitted with well casing — a steel lining that helps prevent blowouts — to at least 300 feet below the ocean floor, Union Oil Co. was given a waiver that allowed it to install casing 61 feet shorter. As the drilling proceeded into a highly pressurized zone of oil and gas, it caused an explosion so powerful that it cracked the ocean floor in five places and prompted the mass spill.
Associated Press
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