In normal conditions arbitrage caps contango at full-carry. Super contango means the arbitrage is unavailable: every tank, cavern and ship is taken, so nobody can buy the spot barrel and store it, and the curve is free to widen until it prices the marginal cost of exotic storage such as floating tankers.
It is a screaming signal of physical distress and it always resolves the same way — production is shut in, demand recovers, storage drains, and the curve flattens or flips to backwardation.
Example: in spring 2020 front-month WTI traded near $20 while the contract six months out traded above $32, a spread far beyond the roughly $0.50 a month that onshore tank storage costs. Traders chartered VLCCs at $100,000 a day purely to store crude.
Related: contango, full-carry, cash-and-carry-arbitrage, negative-oil-price-2020, cushing