UN System-Wide Earthwatch: Tonga
- Environmental information and statistics, including details for individual islands in the group.
- http://islands.unep.ch/CKY.htm

Metis Shoal, Tonga
- Michigan Technological University Volcanoes Page. A new island in the Tonga chain created by a 1995 volcanic eruption. Photographs.
- http://www.geo.mtu.edu/volcanoes/new.zealand/metis/