The CBOE Volatility Index , a popular gauge of stock-market volatility known by its ticker symbol VIX, jumped to a nearly two-month high Thursday as stocks sold off in the wake of President Donald Trump's announcement of new tariffs on $300 billion of Chinese goods. The VIX rose more than 13% to trade above 18.0 for the first time since June 4. Volatility has been subdued, with the VIX trading below its long-run average around 19. Trump, via Twitter, announced the U.S. would impose 10% tariffs on $300 billion of Chinese goods and products beginning Sept. 1, after trade talks this week failed to make much progress. Stocks sold off following the announcement, erasing gains, with the S&P 500 down 0.8% at 2,955 and the Dow Jones Industrial Average falling more than 230 points, or 0.9%.