The selling on Wall Street was so dramatic Monday that it triggered unprecedented emergency freezes on stocks.

Stocks and exchange-traded funds were automatically halted more than 1,200 times, according to Nasdaq.

The high level of trading pauses highlights just how extreme the selloff was in a short span of time. Fears about China’s economic slowdown caused the Dow to plummet over 1,000 points when the market opened. The Dow ended down 588 points, its worst decline since August 2011.

CNNMoney – CNNMoney: Trading was halted 1,200 times Monday