US stocks soared by four percent Wednesday after major central banks joined hands to ensure commercial banks would not be undermined by market worries over the eurozone crisis. Sharply higher from the open, an upward flourish in the last hour pushed the Dow Jones Industrial Average\'s gain to 4.2 percent, while the broader S&P 500 surged 4.3 percent and the Nasdaq Composite added 4.2 percent. The Dow ended the day at 12,045.68, up 490.05 points; the S&P was at 1,246.96, up 51.77, and the tech stock-heavy Nasdaq rose 104.83 to 2,620.34. All 30 members of the blue-chip Dow were higher, led by JPMorgan Chase\'s 8.4 percent gain, Caterpillar\'s 8.1 percent and Alcoa\'s 7.6 percent. Ahead of Wall Street\'s open, the central banks of the United States, the eurozone, Britain, Japan, Canada and Switzerland announced a move to ease fears of a collapse of Europe\'s financial system as lenders tightened credit for eurozone banks. The central banks said they would make cheaper US dollars available to commercial banks facing a lack of liquidity, and also made arrangements to lend each other their various currencies if needed. That drove a strong confidence jump in markets on both sides of the Atlantic, with London\'s FTSE 100 up 3.16 percent, the German Dax adding 4.98 percent and Paris\'s CAC 40 gaining 4.22 percent. Helping was a clutch of other generally positive news. China\'s central bank cut its reserve requirement for banks, a move to boost its economy; Canadian growth for the third quarter came in at a strong 3.5 percent rate; and the US delivered better-than-expected data on private sector job creation, pending home sales and business activity in the important Chicago region. And the Federal Reserve\'s periodic Beige Book review, released Wednesday, described the US economy growing at a \"slow to moderate pace,\" a slightly more positive phrasing than the previous report on October 19. The main driver for stocks came from the concerted central bank move. \"It sends a clear message that central banks are going to do what\'s necessary and to the markets that they\'ll respond to the sovereign debt crisis,\" said Michael James of Wedbush Securities. Banks were big beneficiaries in the day -- despite a general downgrade of most global banks by Standard & Poor\'s on Tuesday: besides JPMorgan, Morgan Stanley rocketed 11.1 percent, Goldman Sachs 7.9 percent, Wells Fargo 7.4 percent, Bank of America 7.3 percent and Citigroup 8.9 percent Shares of American Airlines parent AMR, which crashed 84 percent Tuesday after AMR filed for bankruptcy protection, rebounded six cents to 32 cents for a 23.1 percent single-day gain. US bond prices slumped. The yield on the 10-year Treasury rose to 2.07 percent from 2.00 percent on Tuesday, while the 30-year bond yield climbed to 3.06 percent from 2.96 percent. Bond prices and yields move in opposite directions.