Why did my tire explode? Been running a set of quite nice slicks at 120-140 PSI for a couple of months. Might have done 400-600 km on the bike in that time. Tonight the rear tire exploded while the bike was sitting in my entryway. It's split right along the seam, with a roughly 2 inch long gap. Very loud bang etc.

Before I go out and buy another $70 tire, I want to get an idea of what caused this. Some possibilities that I've thought of include:


Running the tire at 140 PSI. The tire is rated to that pressure, but maybe this is still too much?
Some brief stretches of gravel road (1-2km) I did on it last weekend. The bike seemed fine then however.
There is a central heating/cooling vent directly adjacent to where the bike is stored. Perhaps the changes in temperature were enough to damage the tire?
The roads in this area are not always very good. Maybe this is just the result of accumulated damage from dozens of minor nicks and bumps?
The tire could be defective. 


Edit: added a picture. Looks like the tube has a ~1cm hole in it.
My guess is cords were damaged on the ride creating a weak spot. Threads held together long enough to get you home and a bit longer, then ripped apart. This kind of delayed and catastrophic failure is not uncommon. Heating vent might have softened them enough to make a difference, but the tire was damaged anyway (assuming warm, not very hot air). 

More puncture resistant tires may help prevent it in the future, but you cannot prevent it completely. 

The size of the hole in the tire, and the hole in the tube are irrelevant, its a symptom of the tire failure, not the cause. Once the tire fails, there is nothing stopping the air pressure inside the tube expanding - the tube cannot stop it, it gets pushed though the tire, making that hole bigger and blows up and pops just like a balloon, hence the bang. If you were listening closely, the bang was preceded by a short ripping sound.