Get ready for another blast of head-spinning volatility.
Following the most turbulent market week in years, some strategists are ready to call the all clear. But others say stocks could test the lows of the past week—especially if there are more signs of a weakening global economy; Ebola headlines get worse, or U.S. corporate earnings fail to deliver.
IBM already soured the mood ahead of the opening bell Monday, turning stock futures negative, after its earnings missed expectations.
Read MoreIBM earnings miss the mark
Earnings are expected this week from about 20 percent of the S&P 500, including tech companies, like Apple and Microsoft. Big Dow stocks Boeing, McDonald's, Coca-Cola and Caterpillar join a parade of consumer companies, automakers and industrials.
Earnings will be especially important for sentiment as there is little fresh U.S. economic data with the exception of existing home sales Tuesday and CPI inflation data Wednesday. Chinese retail sales, GDP and industrial production data will be important for markets Tuesday as traders try to assess whether its economy is weakening.