The common denominator was growing fears that governments, central banks and finance ministers seem powerless to stop the deepening of a global recession that will slam corporate earnings and lead to deep job losses around the world.
The Dow Jones industrial average dropped more than 430 points in morning trading. Before the open of New York trading, Dow futures had dropped 550 points, triggering a temporary trading halt in stock futures contracts in an effort to slow the decline. If the Dow drops 1,100 points before 2 p.m. the New York Stock Exchange would be forced to use "circuit breakers" that could lead to temporarily shutting the market, something it hasn't done since 1997.
"This is beyond volatile: It is chaotic," Carl Weinberg, chief economist at High Frequency Economics wrote in note to clients. "This is the kind of day when the central banks step into the market with an 'unexpected' interest rate move to calm things down."
Treasury Secretary Henry Paulson is monitoring the markets and staying in close touch with market participants, a spokeswoman said.
Oil fell sharply and traded near $63 a barrel amid weakening global demand for crude - despite a decision by the OPEC cartel to cut production quotas by 1.5 million barrels a day from next month.
The dollar plunged below 93 yen, a 13-year low. Gold fell as low as $681 an ounce, its lowest since January last year.
It was already a black Friday overseas. Japan's Nikkei stock average dropped 9.6 percent. Germany's benchmark DAX index plunged as much as 10.8 percent, France's CAC40 slid 10 percent and Britain's FTSE 100 shed 8.7 percent.
"We are getting used to wild swings in the markets, but today's moves verge on the bizarre," said Julian Jessop, chief international economist at Capital Economics.
The only good news was the 5.5 percent increase in September existing home sales. Median home prices, however, dropped to $191,600, down 9 percent from a year ago.
The U.K.'s third quarter gross domestic product fell 0.5 percent, with the steepest decrease in 18 years putting the country on the brink of recession. Shares of Japan's Sony sank more than 14 percent when it slashed its earnings forecast for the fiscal year. In Germany, Daimler's stock dropped 11.4 percent in morning trading; it reported lower third-quarter earnings and abandoned its 2008 profit and revenue guidance.
Emerging market economies and currencies are coming under extreme pressure. Investors are pulling money out of countries in Eastern Europe, Latin America and Asia on fears vulnerable countries will not only be hit hard by the financial crisis but may also default on debt.
Hong Kong's Hang Seng index fell 8.3 percent and markets in India, Thailand, Indonesia and the Philippines were also down sharply.
Brazilian stocks slumped for the fourth straight day, with the Ibovespa index down 3.9 percent in midday trading. Mexico's benchmark index was down 6 percent.
"Periods of panic punctuated by occasional calm appears to be the manner of things for now," said Daragh Maher, a strategist at Calyon Corporate and Investment Bank in London.
Investors around the world seemingly have become more convinced the global economy is on the brink of a long and painful recession, if it's not already in one.
Over the past few weeks, governments have taken unprecedented steps to thaw frozen credit markets and avert the downturn. But while there are signs that credit markets are beginning to thaw - rates banks charge each other for short-term loans have been falling in recent days - the outlook from companies reporting earnings are almost universally cautious about their prospects going forward.
That means companies will be reluctant to buy new equipment or hire new workers. U.S. unemployment claims, already well into recession territory, are rising even faster than expected. Economists warn the worst is yet to come.
On Thursday, the government said new applications for unemployment insurance rose 15,000 last week to a seasonally adjusted 478,000, above analysts' estimates of 470,000. Jobless claims above 400,000 are considered a sign of recession.
Goldman Sachs, Chrysler and Xerox all announced they were cutting workers by the thousands, adding to the woes of an economy beset by tighter credit and wobbly banks.
PNC Financial Services said it is acquiring National City bank for $5.8 billion and will receive $7.7 billion in capital from the federal government as part of its $700 billion financial rescue plan.
The White House, in unusually stark language, acknowledged Thursday the economy is going through what spokeswoman Dana Perino called a "rough ride."
"We expect our GDP (gross domestic product) number next week not to be a good one and the next quarter to be tough as well," Perino said.
The Commerce Department will release its first estimate of third-quarter economic performance Oct. 30, and Wall Street analysts project it will show the economy contracted by 0.5 percent, according to Thomson/IFR.
Many economists expect the decline to continue into the current quarter and the first three months of 2009, if not longer. The classic definition of a recession is at least two consecutive quarters of negative growth.
Former Federal Reserve Chairman Alan Greenspan, testifying before a House committee, said he could not see "how we can avoid a significant rise in layoffs and unemployment."
The apparently universal gloomy outlook was feeding the selling.
The Standard & Poor's 500 was down 45.94, or 5 percent, to 867.62. Sam Stovall, S&P's chief investment strategist, put a 700 target on the index, saying S&P's equity analysts expect operating results for the 500 large companies to decline 10 percent in 2008.
Under New York Stock Exchange circuit breakers, if the Dow drops 2,200 before 1 p.m., trading will be halted for two hours. If the threshold is breached between 2 p.m. and 2:30 p.m., the halt will last 30 minutes. Trading will continue to take place if stocks plummet 1,100 points after 2:30 p.m.
If the index falls 2,200 points before 1 p.m., the market will close for two hours. If the decline takes place between 1 p.m. and 2 p.m., there will be a one-hour pause. The market will close for the day if stocks sink 2,200 points after 2 p.m.
In there's a 3,350-point decline, the market would close for the day, regardless of the time.
Associated Press writers Stevenson Jacobs in New York, Louis Watt and Carlo Piovano in London and Martin Crutsinger, Christopher S. Rugaber and Marcy Gordon in Washington contributed to this report.