New York (CNN Business) The bull market is under siege as extreme turbulence grips Wall Street.

The Dow dropped 296 points, or 1.2%, on Friday, capping off another wild week of steep losses and fleeting rebounds.

The Nasdaq tumbled 2.1% as slowing revenue growth from Amazon and Alphabet unnerved investors about richly-valued tech stocks. Amazon plunged 8%, its worst day in four years.

The good news is that markets recovered from even steeper losses. The Dow had been down as many as 539 points and the Nasdaq had plunged 3.6%.

The S&P 500 briefly slipped into a correction before bouncing off the lows.

Still, it was another dreadful week on Wall Street, especially in the tech world. The Nasdaq plunged 3.8% on the week, its worst since March. The index is on track for its steepest monthly decline since November 2008.

"The sentiment in tech is remarkably poor," said Nicholas Colas, co-founder of DataTrek Research. "Technology was priced for perfection. But we live in an imperfect and increasingly unpredictable world."

The bout of volatility reflects mounting worries that the best days of the bull market and economic recovery may be over. The euphoria that carried stocks to record highs has morphed into sudden caution about the future. All of the Dow and S&P 500's gains for the year have been wiped out.

"We see this as much more likely to be a correction as opposed to a bear market," said Evan Brown, head of macro asset allocation strategy at UBS Asset Management. "It's very rare to get a bear market outside of a recession."

Amazon gets grounded

Amazon is ground zero for the intense debate between the bulls and bears.

Although Amazon reported record profit, the e-commerce juggernaut's revenue only increased by 29%. That marks a slowdown from 39% in the second quarter. The weaker-than-expected revenue and outlook underscores concerns that investors got too euphoric about highflying stocks like Amazon.

Google owner Alphabet ( GOOGL ) declined 2% after saying that its revenue growth slowed more than analysts anticipated.

"They've been the momentum stocks. If they go down, they drag the market with them," said JJ Kinahan, chief market strategist at TD Ameritrade.

"Just plain brutal," Paul Hickey, co-founder of Bespoke Investment Group, wrote to clients.

Not all tech results were disappointing though. Intel ( INTC ) recorded stellar chip sales and upgraded its outlook on Thursday. Shares of the chip giant rose 3%.

Even though major companies are minting money, their top-line results have been less impressive. About 57% of S&P 500 companies have reported revenue that beat expectations, according to Refinitiv. That's well below the one-year average of 73%.

Will economic strength last?

Markets are starting to price in slower economic and profit growth as the bull market and business cycle age. The stimulus from tax cuts will eventually fade and the Federal Reserve's interest rate hikes may also weigh on the economy. Trade wars and slowing overseas growth don't help.

In fact, the S&P 500 is now trading below where it was on December 22, 2017, the day President Donald Trump signed the tax cuts into law.

New numbers released on Friday show the US economy grew at a healthy 3.5% pace in the third quarter. The GDP growth, largely in line with expectations, represents a modest deceleration from the brisk 4.2% growth in the fourth quarter.

Colas said he's confident the bull market isn't over. Investors are merely anticipating a deceleration in profit and economic growth.

"I strongly believe this is a correction. Underlying economic fundamentals are still very good," said Colas.