It was an ugly day in the oil market -- the ugliest since 1991.
Oil prices suffered an historic collapse Monday after Saudi Arabia shocked the market by launching a price war against onetime ally Russia.
US oil prices crashed as much as 34% to a four-year low of $27.34 a barrel as traders brace for Saudi Arabia to flood the market with crude in a bid to recapture market share.
Crude settled with a staggering loss of nearly 26% to settle at $31.13 a barrel. Brent crude, the global benchmark, plunged 24% to close at $33.36 a barrel.
Both oil contracts fell to four-year lows.
Read more about the oil drop here.