The 2010 event in which U.S. stocks briefly suffered an extraordinary intraday plunge was the Flash Crash.
On May 6, 2010, major U.S. equity indexes fell rapidly and then recovered much of the loss within minutes. The Dow Jones Industrial Average temporarily dropped almost 1,000 points, an unusually large intraday movement for the period.
Investigations linked the episode to a combination of high-frequency trading, automated order systems, market fragility, and a large sell order. The exact interaction of these forces mattered more than a single isolated trigger.
The Flash Crash differed from a conventional bear market because its most dramatic movement was extremely brief. Some individual securities traded at implausible prices, leading exchanges and regulators to cancel certain transactions and strengthen safeguards against similar disruptions.