Drive on Interstate 10 along the Gulf Coast of the United States, through Louisiana and into Texas, and you’ll see signs of the oil industry everywhere. There are offshore rigs out in the water and refineries lining the shoreline, where tankers deposit crude oil extracted from the Gulf floor.

But what you might not realise from looking at the surface, is that this area is also home to a network of underground salt deposits, known as salt domes.

And dug down deep inside them are caverns, carved out in the late 1970s, that contain the  Strategic Petroleum Reserve, America’s huge stockpile of oil. 

Current stocks stand at 374 million barrels worth of oil, well short of its capacity of 714 million barrels.

With the........

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