After weeks of cautioning that the spectacular run-up in stocks was likely to hit a snag, a dramatic sell-off shook Wall Street on Thursday.

The tech-heavy Nasdaq Composite plunged 5%, its worst day since June. The Dow dropped 2.8% and the S&P 500 fell 3.5%. Shares of Apple and Tesla, which had been on a tear since they announced stock splits that made shares more affordable, plummeted 8% and 9%, respectively.

The action came after a summer of hand-wringing as stocks continued to reach new records, driven by massive central bank stimulus and unbridled enthusiasm for tech companies. As Apple’s valuation topped $2 trillion, more than the entire Russell 2000, strategists had been telling clients that a correction was inevitable.

Bespoke Investment Group noted that some of the worst-hit stocks had been “the most aggressively valued and the biggest gainers” so far this year. And with tech looking like a very crowded trade, a rotation into other sectors is likely a good thing.

“With such a stellar run, I would expect there would be a readjustment in stocks,” Susannah Streeter, senior analyst at Hargreaves Lansdown, told me.

The question now is whether Thursday’s rout marks the beginning of a more prolonged period of selling, or if it amounted to one-time profit-taking ahead of a holiday weekend.

Closely-watched measures of volatility indicate that the turbulence could continue. The CBOE Market Volatility Index, or VIX, which tracks volatility in the S&P 500, fell back slightly Friday but remains elevated, which is unusual when stocks are near all-time highs.

Meanwhile, the CBOE Nasdaq Volatility Index — which follows the Nasdaq 100 — continued to climb. It’s now at its highest level since April.

“There might be a bit of a bumpy road ahead,” Streeter said.

Still, she noted that tech shares aren’t likely to go fully out of favor any time soon given their perks as a defensive bet during the pandemic. Tech companies have been far less affected by social distancing than many other firms, allowing them to continue to reap huge profits. For investors looking for safe returns, that’s hard to ignore.

“Valuations are extended on all measures except relative to bonds,” Bank of America strategists told clients on Thursday. “But liquidity is abundant, with dry powder at private and public funds, high cash allocations among individuals, still tepid sentiment on stocks, and not a lot of better income options than US equity dividends.”