In her first congressional testimony as Fed chair, Janet Yellen on Tuesday reassured markets that she is just as dovish as her predecessor and that the central bank will not be quick to pull away from stimulus.

Her comments sparked a sharp jump in stocks and fired up a rally that continued into the afternoon session. The Dow was up more than 1 percent at 15,985, and the Nasdaq hit a new high for the year, rising nearly 1 percent. The S&P 500 also was up nearly 1 percent, breaking key technical levels of 1,800 and 1,810.