Hydrolysis is a problem which causes major irritations with hiking boots. From one step to the next, the sole falls off.
Your soles just crumbled off your boots. Why? And what now?
Hydrolysis is a long term effect on the PU based damping sole of modern hiking boots. Over time, the water will break down the structure of the PU cushioning layer and then from one step to the next, the sole falls off.
Unfortunately a lot of people get pissed off and throw the boots away, swearing never to buy that brand of boots again. But all good quality brands suffer from this problem as it only occurs in good quality PU. Which means you bought a good quality pair of boots.
There is good news, though. The effect of hydrolysis are generally only seen somewhere between 8 and 12 years after manufacture. And the more you wear the boots, the longer it takes to happen, due to the material keeping it's elasticity with the usage. Also, many hiking boots which can suffer from hydrolysis can be resoled. But the best remedy is to wear the traction sole out before the hydrolysis can take place, and then get them resoled anyway!
So if you're planning a long hike in the near future, but are concerned about the age of your boots and are happy with the fit, get them resoled ASAP. If it was your car, you wouldn't wait for a blowout before replacing the tyres.