The major U.S. stock indexes moved modestly higher in late-afternoon trading Monday after spending much of the day veering between gains and losses. Materials and health care stocks were among the biggest gainers, while energy stocks fell the most following another steep slump in crude oil prices.

Investors were weighing the latest batch of company earnings news and looking ahead to the beginning on Wednesday of two days of testimony before Congress by Federal Reserve Chair Janet Yellen.

KEEPING SCORE: The Dow Jones industrial average was up 38 points, or 0.2 percent, to 16,061 as of 3:21 p.m. Eastern Time. The Standard & Poor's 500 gained five points, or 0.3 percent, to 1,858. The Nasdaq composite added six points, or 0.1 percent, to 4,289. Stocks posted steep slides Monday and Friday.

THE QUOTE: "The market has been trying to define a direction, leadership," said Quincy Krosby, market strategist for Prudential Financial. "But the pockets of uncertainty continue. That's part of what's holding the market back."

SECTOR TALLY: Six of the 10 sectors in the S&P 500 index moved higher, with materials stocks leading the gainers. Energy stocks posted the biggest decline, 2.3 percent.

RIDING HIGH: Martin Marietta Materials vaulted 11.1 percent after the construction materials company reported a sharp increase in earnings. The stock was the biggest gainer in the S&P 500 index, climbing $13.11 to $130.96.

A BOOST: Boston Scientific climbed 4.7 percent after the medical device maker said the Centers for Medicare and Medicaid will cover an additional key treatment for its Watchman device. The stock added 75 cents to $16.83.

SALES CONCERNS: Viacom tumbled 18 percent after the owner of Nickelodeon, MTV, Comedy Central and Paramount Pictures reported a worse-than-expected drop in fourth-quarter revenue on lower ad sales. The stock dropped $7.54 to $34.31.

OIL EFFECT: Several energy sector companies slumped as the slide in crude oil prices deepened. Consol Energy lost 88 cents, or 10.2 percent, to $7.68, while Southwestern Energy fell $1.08, or 13.6 percent, to $8.26. Murphy Oil slid $1.30, or 6.8 percent, to $17.93.

MIXED RESULTS: Bristow Group tumbled 26.5 percent after the helicopter services company reported better-than-expected fiscal third-quarter profit, but revenue fell short of forecasts. The stock lost $4.90 to $13.58.

ROUGH GOING: Stock markets have endured a torrid start to the year as investors have fretted over a number of issues, including the fall in the price of oil to multi-year lows, a slowdown in China and whether many parts of the global economy will fall into recession and suffer a debilitating period of deflation, or falling prices. Global equities have now lost about $6 trillion since the start of the year. In January, that was largely due to worries over the slowdown in China and the slump in the price of oil.

EYES ON THE FED: Yellen is scheduled to addresses Congress over two days Wednesday. Yellen will outline the central bank's outlook on the economy. Investors will be watching for hints about when the Fed will make its next move to raise its key interest rate. Most analysts and investors think the Fed will raise rates fewer than four times this year, if at all.

EUROPEAN MARKETS: Stocks managed to eke out early gains in Europe before succumbing to another bout of selling. The FTSE 100 index of leading British shares was down 1 percent, while Germany's DAX fell 1.1 percent. The CAC-40 in France was 1.7 percent lower.

ASIA'S DAY: Japan's Nikkei index tumbled 5.4 percent and the interest rate on the country's benchmark bond dropped into negative territory for the first time. The yields on Japan's bonds have been low for years as the country kept its interest rates at or near zero.

ENERGY: Crude oil prices fell sharply for the second day in a row Tuesday. Benchmark U.S. crude oil dropped $1.75, or 5.6 percent, to close at $27.94 a barrel in New York. Brent crude, a benchmark for international oils, fell $2.56, or 7.8 percent, to close at $30.21 a barrel in London. The International Energy Agency, which advises countries on energy policy, said oil prices will continue to come under pressure as supply is set to outpace demand this year.

METALS: Precious metals prices were mixed. Gold rose 70 cents, or 0.1 percent, to $1,198.60 an ounce and silver inched up 2 cents, or 0.1 percent, to $15.44 an ounce. Copper, an industrial metal that will often rise and fall along with investor's optimism about the global economy, fell 5 cents, or 2.4 percent, to $2.04 a pound.

BONDS AND CURRENCIES: Bond prices rose. The yield on the 10-year Treasury note fell to 1.73 percent from 1.75 percent late Monday. The dollar was down at 114.99 yen from 115.58 yen. As recently as the end of January, the dollar was trading above 121 yen. The euro up $1.1286 from $1.1186.