When visiting New Zealand earlier this year, I climbed Mt Ruapehu – well, some of it anyway. At the time, I marvelled at the sternly worded warning signs like: “Did you know? Volcanic mud travels down gullies” and “Do you know what to do when the siren sounds?”
After watching this (from 2007), I can see why. Volcanic lahars – now on my list of things I wouldn’t want to be swept away by.