Today: Stocks deflate and price of oil rises as investors exhibit concern that U.S. could strike Syria in response to chemical-weapons usage. Also: Silicon Valley's quarter of CEO changes continues, Workday and TiVo announce earnings.

The Lead: Indexes tank, oil price spikes as Syrian fears increase

Wall Street had its worst day in more than two months Tuesday, as indexes plummeted and the price of oil spiked amid fears that the U.S. could intervene in Syria's civil war after the country's leader reportedly used chemical weapons against his own people.

All three major U.S. stock indexes dropped more than 1 percent, led by the tech-heavy Nasdaq, which declined 2.2 percent to fall below 3,600. The price of oil, meanwhile, climbed higher than $109 a barrel for the first time in more than two years, as traders fretted that Syrian ally and major oil producer Iran could be dragged into the conflict.

"The issue, of course, is not Syria itself but certainly, factions within Syria that are clients of Iran," Tradition Energy director Addison Armstrong told the Associated Press.

Secretary of State John Kerry said Monday that it was "undeniable" that Syrian President Bashar Assad's government had used chemical weapons in its battle with rebel forces; Syria's foreign minister responded Tuesday by saying that the country would use "all means available" in case of a U.S. strike.

Traders feared that a Middle East conflict could endanger the fragile global economy, with the United States possibly most in danger.

"It further adds to the degree of uncertainty that's out there," Huntington Asset Advisors chief investment officer Randy Bateman told Bloomberg News.

"Is this going to escalate? Energy prices, if they rise a whole lot, could that mitigate all the strength we've been seeing lately in the economy? If we've got housing prices that start to rise at the same time we have food and fuel increasing, we could see inflation start to rise and that could impact Fed policy," he explained.

Like oil traders, investors were also concerned that any conflict could escalate beyond just Syria.

"This (Wall Street) move is as much about the potential spillover effect in the region as it is the potential for a U.S. strike," BNY Mellon Wealth Management chief investment officer Leo Grohowski told Reuters.

"People worry about this becoming a worst-case scenario and turning into a regional conflict," Bill Stone, chief investment strategist at PNC Asset Management, agreed in an AP interview.

SV150 market report: Another CEO switch, Workday and TiVo announce earnings

Silicon Valley stocks couldn't avoid Tuesday's downturn, with the SV150 mirroring the Nasdaq's 2.2 percent decline as yet another tech company announced the departure of its CEO.

San Jose chip company Integrated Design Technology announced Monday evening that its CEO, Tom Tewksbury, had resigned, effective Tuesday; he will be replaced on an interim basis by former Texas Instruments executive Jeffrey McCreary, a member of the company's board for slightly more than a year. IDT is the sixth SV150 company to announce a change at the top this quarter, following Zynga, Juniper, Polycom, Applied Materials and Solta Medical. IDT stock declined 4.5 percent to $8.32 on the day.

IDT was not alone: Only eight companies in the SV150 managed a gain Tuesday, a group that included Tesla Motors (TSLA), which increased 1.7 percent to $167.01, giving it a closing market capitalization higher than $20 billion for the first time, after the Palo Alto company closed barely below the mark Monday. Facebook, which eclipsed the $100 billion market cap plateau Monday, was among the larger group of decliners, with the Menlo Park social network dropping 4.1 percent to $39.64 after releasing details about global requests for user information for the first time. Apple (AAPL) fell lower than $500, declining 2.9 percent to $488.59 while announcing an update to Apple TV, but the judge in the company's e-books battle with the federal government said she would like to avoid materially affecting Apple's business. Intel (INTC) fell 0.4 percent to $22.19 amid rumors about a 3D laptop camera and its TV effort, while Yahoo (YHOO) declined 2.5 percent to $27 on the same day it redesigned many of its important properties.

After the markets closed, two SV150 companies announced quarterly earnings. Pleasanton-based Workday, nearing the one-year anniversary of its initial public offering, showed off continuing revenue growth, reporting a 72 percent year-over-year boost to its quarterly sales, which checked in at $107.6 million. The company is still losing money, however, reporting a loss of 21 cents a share; after finishing the day with no change at $76.01, Workday stock slipped less than 1 percent in late trades. San Jose-based TiVo saw its shares head north after reporting its quarterly earnings -- the television-tech company brought in profits of $1.96 a share on revenues of $100.1 million. TiVo, which recently launched its latest digital video recorder, dropped 1.6 percent to $10.97 in regular trading, but moved 1.8 percent higher in after-hours action.

Up: Ubiquiti, Tesla, Yelp

Down: SunPower (SPWRA), SolarCity, Advanced Micro Devices, Facebook, Pandora, VMware, Zynga, Electronic Arts (ERTS), Juniper, Apple, Gilead, LinkedIn, eBay (EBAY), Yahoo, Applied Materials, Netflix (NFLX), Symantec, Salesforce, Google (GOOG), Oracle

The SV150 index of Silicon Valley's largest tech companies: Down 29.31, or 2.24 percent, to 1,277.01

The tech-heavy Nasdaq composite index: Down 79.05, or 2.16 percent, to 3,578.52

The blue chip Dow Jones industrial average: Down 170.33, or 1.14 percent, to 14,776.13

And the widely watched Standard & Poor's 500 index: Down 26.3, or 1.59 percent, to 1,630.48

Check in weekday afternoons for the 60-Second Business Break, a summary of news from Mercury News staff writers, The Associated Press, Bloomberg News and other wire services. Contact Jeremy C. Owens at 408-920-5876; follow him at Twitter.com/jowens510.