The S&P 500 fell 1.5% and resumed its sharp swings following a couple days of relative calm. The Dow Jones Industrial Average dropped 739 points, or 1.6%, and the Nasdaq composite lost 1.8%.

The center of action was again the oil market, where the price of a barrel of Brent crude, the international standard, climbed 9.2% to settle at $100.46. Worries are worsening that the war could block the production of oil in the Persian Gulf for a long time and cause a debilitating