In geology (and sometimes in archaeology), a high island is an island of volcanic origin. The term can be used to distinguish such islands from low islands, whose origin is due to sedimentation or uplifting of coral reefs.
Tafahi is a small (1.2 km × 2.8 km or 0.75 mi × 1.7 mi) island in the north of the Tonga archipelago, in fact closer to Savaiʻi (Sāmoa) than the main islands of Tonga. It is only 9 km (5.6 mi) north-northeast away from Niuatoputapu, and fishermen communicate in small outboard motorboats almost daily between the two.
Other names for Tafahi are Cocos Eylant (coconut island) or Boscawen island.