It shrinks in the cold, expands in the heat, and bends when a load is put upon it. In cooler weather it gets stiff, in warmer conditions slick and greasy. It's under continuous stress every moment of every day, from wheels turning upon it to temperature changes beating it down to water looking for a crack to sneak into. At a certain point, it just can't take anymore, and it begins to crumble.

And a pothole forms.

What happened at Daytona International Speedway last weekend was far from unique, in the sense that asphalt paving anywhere, be it on a highway or a race track, faces a host of physical, chemical and environmental hazards that threaten to eventually break it down. You see it on the road every day, in the form of ruts and fissures that form after some combination of age, freezing, thawing, water and load becomes too much. You see it occasionally in NASCAR, like the chunk that tore out of Martinsville Speedway and punched a hole in the radiator of Jeff Gordon's car in 2004.

Kurt Busch waits out Sunday's delay with officials on pit road.

Asphalt is a substance that's under constant attack from heat, cold, rain, and whatever traverses upon it, and has its limits like anything else.

But we've never seen it happen on such a grand stage, in the middle of the Daytona 500, the one race that attracts more attention and more viewers than any other, the one race where NASCAR can't afford to have something of that magnitude go wrong. Yet there it was, that crater in the low groove of Turn 2, a hole that prompted two lengthy, uncomfortable, buzz-killing delays, and hijacked an event and a Speedweeks that otherwise was everything NASCAR needed it to be. The record 21 leaders, the 52 lead changes, the action stoked by the rule changes, breathtaking late-race moves made by Kevin Harvick, Dale Earnhardt Jr., and winner Jamie McMurray -- remove one pothole from the equation, and Sunday would have been very close to a perfect day.

But you can't remove it. It was right there, obvious every time the cars passed over it, an adventure that often resulted in vehicle damage, driver excoriations, or both. As a result NASCAR is getting upbraided by the casual sports press that the circuit's premier event tends to attract. The New York Times called it "a stunning failure." ESPN talking head J.A. Adande called it "a setback for the sport." Excluding the delays to repair the track, overnight television ratings for the live race portion of the 500 dropped 16 percent to their lowest level since 1991. People compared Sunday's events to a hole in the field delaying the NFL's Super Bowl -- something that's never happened, and probably never will. The timing could not have been worse.

All of this because of pavement, that wide swath of black that the cars compete on every week, perhaps the single most taken-for-granted element in NASCAR racing, but as Sunday proved one that can wreak absolute havoc when it decides it's had too much. It looks so simple, so permanent, so impervious. And yet, the people who work with it for a living know it's anything but. Asphalt is a substance that's under constant attack from heat, cold, rain, and whatever traverses upon it, and has its limits like anything else.

"When you pave a new piece of pavement, the moment it's put down it begins to age. Asphalt ages as it oxidizes, and it starts changing its chemical properties from day one, from moment one," said Michael Harnsberger, principal scientist at the Western Research Institute, a Laramie, Wyo., nonprofit that studies highway materials. "As its chemistry changes, its physical properties change. As it ages it becomes stiffer, and when it becomes stiffer it becomes generally less flexible, and it also becomes more susceptible to water invading the bond between the asphalt and the aggregate. If water gets it there and disrupts that bond, and the bond breaks, then the asphalt and the aggregate come apart." (Continued)