Dow Jones Indices: Jul 31 4:33 PM ET 

Dow plunges over 300 points, erasing its gains for the year

Geopolitical worries weigh on investors; Dow sees biggest drop since February.

Geopolitical worries weighed on investors Thursday, with the Dow Jones industrial average dropping 317 points and leading a broad market retreat that left the blue-chip index down for the year.

By the close of trading, the Dow had chalked up its biggest drop since February.

In addition to the Dow’s sharp slide, the S&P 500 index and the Nasdaq both fell 2% in afternoon trading. The Dow is now lower than where it began the year. In July, the index crossed the 17,000-point mark for the first time ever as broader market indexes hit multiple record highs.

The Chicago Board Options Exchange Volatility Index (VIX), known as the “fear index,” rose 27%, hitting a multi-month high.

Contributing to the market’s retreat: news late Wednesday that Argentina’s credit rating has been downgraded to selective default by Standard & Poor’s.