Market Update Wed, Jan 23, 2008, 4:25AM ET - U.S. Markets closed.

4:25 pm : There are volatile markets and then there are volatile markets. Wednesday's session was the latter variety, which is to say it was truly volatile. To wit, the swing in the S&P 500 between its low of the day, reached around 12:45 p.m. ET, and its high of the day, reached around 3:50 p.m. ET, was 69 points or 5.4%.

The bearish mood that predominated for the first half of today's session was driven by a relatively disappointing earnings report and outlook from Apple (AAPL 139.07, -16.57) and a remark from ECB President Jean-Claude Trichet that left participants inclined to believe the ECB won't be following the Fed's lead and cutting its key bank rate.

The latter precipitated a widespread sell-off in European bourses, most of which dropped between 3.0% and 5.0% for the day. Their poor showing carried over to the U.S., which was already on the defensive amid consumer spending concerns that flowed from Apple's conservative outlook.

Briefly, Apple forecast fiscal second quarter sales of $6.8 billion and earnings of $0.94 per share versus analysts' expectations of $6.98 billion and $1.09, respectively.

Correspondingly, the tech sector led the early retreat along with the energy, telecom, and materials sectors, which traded down sharply on growth concerns. Those concerns were reflected in falling oil prices, which hit $86.65 a barrel at their low before rebounding some to $87.59 at the end of the trading session.

The energy sector declined as much 6.3% at its low today. Remarkably, it closed with a gain of 0.6% after participating in the afternoon rally.