OSLO (Reuters) - A chunk of an Arctic glacier broke into the sea and triggered a huge wave that injured 18 people on a sightseeing boat, almost all of them British tourists, Norwegian officials said on Thursday. Four people were seriously hurt in the accident by Hornbreen glacier on the Norwegian archipelago of Svalbard and were flown south to a hospital in Tromsoe on the mainland. The others were treated at a local hospital, mostly for minor injuries. "The glacier calved (split off) and a big wave washed over the boat," Elisabeth Bjoerge Loevold, acting governor of Svalbard, told Reuters....