US STOCKS-Wall St posts worst day in four years, S&P 500 now in correction
* All three major U.S. indexes tumble, now confirmed in correction
* Soon after the open, Dow was down more than 1,000 points
* Apple mostly recovers after falling as much as 13 percent
* Indexes close down: S&P 3.94 pct, Nasdaq 3.82 pct, Dow 3.58 pct (Adds details on stock futures open)
By Noel Randewich
Aug 24 (Reuters) - U.S. stock indexes plunged almost 4 percent on Monday as investors, rattled about China's economy, sold heavily in an unusually volatile session that confirmed the benchmark S&P 500 was formally in a correction.
The Dow Jones industrial average briefly slumped more than 1,000 points - its most dramatic intraday trading range ever - with key component Apple falling heavily only to claw back but end down 2.5 percent.
It was the S&P 500's worst day since 2011 and followed an 8.5 percent slump in China markets, which sparked a sell-off in global stocks along with oil and other commodities.
Wall Street had stayed in a narrow range for much of 2015, but volatility returned this month as investors became increasingly concerned about a potential stumble in China's economy and after Beijing surprisingly devalued its yuan currency. Continuación...