How deep can a submarine volcanic vent be and still generate a significant pumice raft ? Sadly, Wiki is a stub, and most of the relevant literature is pay-walled. As I understand it, deep vents may generate a lot of pumice, but it never reaches the surface, just stays on the vent's flanks. The famous mega-rafting in 'South Pacific' came from a transient volcanic island, clearly visible on the bemused yachties' photos. Unlike Surtsey, it didn't endure... Would a kilometre-submerged rifting event, eg in Canary chain, produce significant, persistent rafting ??