The stock market couldn't shake off a case of the jitters from last week and closed sharply lower again on Monday.
Airlines, energy and materials stocks were among the biggest decliners. The market is coming off its biggest weekly decline in more than two years.
Many investors remain concerned that economic growth in Europe and Asia could be slowing. A meeting of Eurozone finance ministers in Luxembourg didn't appear to ease those concerns.
A measure of volatility soared, indicating investors are getting increasingly nervous.
"There is a sense that ... the U.S. maybe can't go it alone, that if global growth continues to weaken, the U.S. is not going to be able to sustained the kind of momentum we've been gaining since the first quarter," said Quincy Krosby, market strategist at Prudential Financial. "That's the worry."
A late slide in the last half-hour of trading came after an otherwise calm day in the markets. Index futures had pointed to a higher open in premarket trading early Monday, then the market opened lower and wavered for much of the day between small gains and losses.
The late wave of selling was likely triggered by automated trading programs that started selling stocks when it became clear that the S&P 500 would close below an important technical level, said Randy Frederick, managing director of trading and derivatives at Schwab Center for Financial Research.
Many traders follow these levels to give them an indication about the near-term direction of the market.
In this case, the S&P 500 closed below 1,905, the 200-day moving average price for the index. The index had traded above the average since November, 2012, gaining 36 percent.
"We've broken down to a point where we haven't been for a long, long time," Frederick said.
Frederick still thinks the stock market will avoid a "correction." That's Wall Street talk for a drop of 10 percent or more, something that hasn't happened since October 2011. Frederick is expecting the recent volatility to continue for a few more weeks yet.
All told, the Dow Jones industrial average lost 223.03, or 1.4 percent, to 16,321.07. The Standard & Poor's 500 index shed 31.39, or 1.7 percent, to 1,874.74.
The Nasdaq slid 62.58 points, or 1.5 percent, to 4,213.66.
The VIX, a measure of volatility that is commonly called Wall Street's "fear index," climbed 12.7 percent to 23.95, its highest level since June 2012.
All of the 10 sectors in the S&P 500 fell, led by energy with a decline of 2.9 percent. Utilities, a safe-play sector, fell the least, just 0.1 percent.
The downturn leaves the S&P 500 up just 1.4 percent for the year and down 6.8 percent from its recent peak of 2,011.36 reached on Sept. 18.
The Dow went negative for the year on Friday and is now down 1.5 percent for 2014 and 5.5 percent below its September peak. Small-company stocks have fared much worse than the rest of the market as investors shun investments seen as more speculative. The Russell 2000 index has fallen 13.2 percent since July.
Airline stocks had some of the biggest declines on Monday. That sector has received a drubbing from investors recently as worries mount that the outbreak of the Ebola virus will curb travel spending. Concerns about a slowing global economy have also hurt the stocks.
American Airlines Group fell $2.20, or 7.1 percent, to $28.58 and Delta Air Lines fell $2.01, or 6.1 percent, to $30.90. American has fallen 24 percent in the last month, Delta 22.2 percent.
Investors found reasons to cheer some stocks.
CSX led the gainers in the S&P 500 as investors reacted to a published report that another railroad operator has approached the company about a possible merger. The stock climbed $1.76, or 5.9 percent, to $31.70.
Atlas Energy vaulted 14.9 percent on news of its acquisition by Targa Resources Partner. Atlas Energy added $4.84 to $37.25.
Investors were looking ahead to earnings news from a number of big companies later this week including General Electric, Intel and Bank of America.
Despite the recent volatility in the markets, the overall earnings outlook is good.
Third-quarter earnings growth for companies in the S&P 500 is expected to be about 6.8 percent compared with the same period a year ago, according to S&P Capital IQ.
If earnings live up to or exceed analysts' forecasts, that could help reassure investors, said Karyn Cavanaugh, senior market strategist at Voya Investment Management.
"These companies haven't changed from two months ago, when we were talking about all-time (market) highs, to today," Cavanaugh said. "These are still good companies, with good value and good earnings potential."
The price of U.S. oil slipped slightly and the global oil price fell sharply on expectations that OPEC countries will not cut output in response to lower global demand.
Benchmark U.S. crude fell 8 cents to close at $85.74 a barrel on the New York Mercantile Exchange. Brent crude, a benchmark for international oils used by many U.S. refineries, fell $1.32 to close at $88.89 on the ICE Futures exchange in London.
In other energy futures trading on the NYMEX, wholesale gasoline fell 0.3 cent to close at $2.255 a gallon, heating oil fell 0.3 cent to close at $2.557 a gallon and natural gas rose 5.7 cents to close at $3.916 per 1,000 cubic feet
Gold rose $8.30 to $1,230 an ounce, silver rose four cents to $17.35 an ounce and copper was flat at $3.04 a pound.
Bond trading was closed for Columbus Day.