In the 1970s President Nixon severed the dollar's link to gold. The result was a falling dollar measure that revealed itself through rising nominal prices of oil, wheat, soybeans, and much else priced in the global currency. It's not as though the commodities mentioned were suddenly scarce as much as the dollar shrunk in size. Probably the best way to think of it is if the foot were cut in half to six inches, Kim Jong-Un would suddenly stand over 10 feet tall even though his actual height wouldn't change one iota. That's what happened with commodities like oil in the ‘70s, and it explains $70 oil today. The commodity isn't scarce as much as the dollar is once again shrunken.
Notable about the ‘70s is that politicians, totally confused by what was a monetary error on the part of Presidents Nixon and Carter, imposed price controls on gasoline. The result was lines at the gasoline pump. Long ones. When the price of anything is artificially suppressed, scarcity is a certainty. No surprise there. So bad was it in California that endlessly deluded lawmakers instituted an odd/even system. Cars with license plates ending in an odd number were only legal to purchase gas at the filling station on odd numbered days, and vice versa.