Stocks soared today after the Federal Reserve did what Wall Street was clamoring for and cut its key discount rate a half percentage point. The move quelled investors’ credit worries at least for the time being and sent the Dow Jones industrials up about 230 points.

The Fed — which had resisted lowering rates despite weeks of market volatility, and instead added nearly $120 billion in liquidity into the banking system — cut its discount rate to 5.75% from 6.25%. The central bank acknowledged that the stock market turbulence that has pulled the Dow by hundreds of points a day was posing a risk to economic growth.

“People were kind of baiting the Fed into doing something, and finally they did,” a managing director of equity trading at RBC Dain Rauscher, Philip Dow, said. “The playground monitor finally showed up, and it showed someone cares and someone is bringing rationality into the market.”

But the central bank made no mention of lowering its target for the federal funds rate, which has stood at 5.25% for more than a year. The fed funds rate determines the rates that banks charge each other, while the discount rate only covers loans the Fed makes to banks. Many strategists believe the market won’t settle down until the Fed lowers the fed funds rate target, considered a more significant benchmark.

If the market doesn’t get that rate cut, today’s gains may not stick, especially since it’s likely there will be plenty more news in the coming days and weeks of further troubles in the lending industry. Any mention of problems at subprime lenders or funds that invested in mortgages has sent stocks skidding, and so have worries that tighter credit will stanch the flood of takeovers, which sent Wall Street to new highs earlier this year.

Still, the Fed made it clear this wasn’t the only step it would take if the volatility continued. In its statement, the Fed said it “is prepared to act as needed.”

According to preliminary calculations, the Dow Jones industrial average surged 233.30, or 1.82%, to 13,079.08.

Trading was still volatile throughout the day, with the Dow rising more than 320 points in early trading, giving up more than half those gains, and then gaining steam once more. However, the blue chip index stayed in positive territory the whole time. The Dow is more than 6% below its record close of 14,000.41 reached July 19, and is down more than 1% for the week.

The Standard & Poor’s 500 index rose 34.65, or 2.46%, to 1,445.92, and the Nasdaq composite index rose 53.96, or 2.20%, to 2,505.03.

Bonds slipped as stocks rose, with the yield on the benchmark 10-year Treasury note rising to 4.67% from 4.66% late yesterday.