Deluge systems have been used for a long time. At least as far back as Apollo. It absorbs the shock waves from all that thrust. It does some cooling but mostly absorbing shock by flashing to steam and cushioning the pressure waves. It's still basically a massive controlled explosion. You can see it really well in the Shuttle launches but not so much Apollo. What you also see is that the pad is pretty much incinerated. One of the reasons for long turn around times. As far as ditching the pads are raised and there is a large pit there to direct the thrust away from the pad. Search for launch pad videos on you tube.