Yes, Brian, I felt as I typed that the 1960's type photo was not in line with my conclusion... I therefore have to go for the island Surtsey off Iceland in 1963-67 (as it took 4 years of euruption to make the island rise from the sea)
It was November 1963- we were up there on Fishery protection.We recieved a signal from there lordships to investigate and if possible get a sample of the volcanic ash. We sailed under that cloud to do just that and ended up with six inches of the stuff on the upper deck. It took two days to hose the bloody stuff away.