I've just re-read your link which gives surprisingly in-depth details about the geology of the area. It was one of those pointless acts of vandalism that initially leaves you speechless - I have a friend who works for the probation service and he would say there is almost always alcohol behind most anti-social crimes. Realistically, if they were ever prosecuted (and are over 18) they would probably get a Community Payback sentence - picking litter up in the local park or some such activity. Sadly, not really restorative.