Are road bikes capable of being ridden on gravel?
I am new to road bikes and was wondering if these bikes are capable of riding on light gravel or whether I will get flats? Does it depend on the tire material or are generally all road bike tires for road only?
What do you understand as "light gravel"? What are you trying to do? A short stretch of gravel won't kill the tires, but a road bike is not really for forest trails.
A "road" bike, other than the most lightly built, can handle a well-packed gravel road/trail with minimal loose gravel. The biggest problem is that the skinny tires will not handle loose gravel well at all. Ordinary limestone gravel is not particularly hazardous to tires (though gravel composed of, say, crushed volcanic rock might be a problem).
You can get narrow, knobbly 700C tyres, like the Schwalbe Cyclocross ones. Typically they're somewhat on the fat side for most road frames but you might squeeze one in (their skinniest one is 30mm). I do it the other way round and ride a cross frame with road tyres (mostly because it has disk brakes)
One thing when riding a "road" bike on gravel: Plan ahead as you ride and watch the distribution of the gravel on the road. Traffic will smooth out the tire tracks and often they're asphalt-smooth as a result. But at curves and intersections gravel may be spread around randomly. Plan your path along the road to stay on the smooth, relatively gravel-free surface (while, of course, staying reasonably clear of auto traffic).
The primary difference between a road bike and a CX bike is the size of the tires. You can ride your road bike anywhere your skills will allow. There are some gotcha's though.
Skinny tires only have so much traction. Gravel flats won't be an issue for all but the lightest of race tires, but pinch flats from hitting larger rocks at high speed are a problem.
Dirt and high end road components don't mix well.
But seeing exactly how far you can take a road bike has a long history and many local clubs have "grasshopper" rides that link up old gravel roads. Your bike is capable of much more than you might think. Look up the races Paris-Roubaix and Strada Bianca.
Theres also different geometry to most road racers (like bottom bracket placement for stability). But tire size is probably the most important factor.
The Bike Party 1 & 2 are the extreme example of what a road bike is capable of, essentially anything you could want to do on a bike. The only damage to the bike in the 2nd movie was a puncture.
It heavily depends how packed the surface is as well: plenty of people ride the (Loire à Vélo)[http://www.cycling-loire.com/cycling-loire-map] on road bikes/tourers with road tyres despite some parts being improved farm tracks - but there's only a thin layer of loose material on these unpaved stretches (at least the ones I've ridden).