- Tonga has been named Kingdom of Fire with its volcanic history and 4# current active volcanic systems and another 11# that have erupted in the past 100 years. Some are subaerial and some are submarine volcanic systems.
- The Tongan islands are a double island chain – the older eastern chain is gabbro-basalt-andesite covered with limestone and the younger western chain are active volcanoes. Plate tectonics here has meant that Tonga is actually rising elevation faster than sea levels are rising.
- Tofua is the summit of a large stratovolcano that is thermally and gaseous active. Agricultural island.
- An interesting feature is the presence of significant submarine hydrothermal systems along the South Tonga Ridge and the nearby Valu Fa Ridge. Eleven ocean hydrothermal systems have been found on these ridges emanating from seven volcanoes, temperatures of 245-265°C were recorded at depths of 385-540 m. Future potential resources?
