Tofua

Tofua Caldera, in Tonga, is the summit caldera of a steep-sided composite cone that forms Tofua Island. Pre-caldera activity is recorded by a sequence of pyroclastic deposits and lavas constituting the older cone, followed on the northern part of the island by froth lavas or welded and unwelded ignimbrite. Following caldera collapse, lavas were erupted from the northern part of the island and the caldera-rim fissure zone, scoria and lavas from the caldera-wall fissure zones, pyroclastics and lavas from intracaldera cones, and recent pyroclastic fall deposits on the outer cone. Eruptive products are mainly basaltic andesites and andesites, plus occasional dacite flows within the older cone. A postcaldera cone with fumarolic activity (Lofia) is situated in the northern part of the caldera; a crater lake of unknown depth occupies most of the remainder.

Most historical eruptions have been small explosions from Lofia cone along the northern caldera rim. The eruptions of 1958-59 caused most of all islanders to evacuate for a year or more.

Tofua Island

Tofua has a population of about fifty. They are there primarily to grow kava ("Piper methysticum") for export to Tongatapu.

Tofua in History

The Mutiny on the Bounty (1789) took place about 30 nautical miles (56 km) from Tofua. Captain William Bligh navigated the overcrowded 23 foot (7 m) open launch on an epic 41-day voyage first to Tofua and then to Timor equipped only with a sextant and a pocket watch -- no charts or compass. He recorded the distance as 3,618 nautical miles (6701 km). He passed through the difficult Torres Strait along the way and landed on June 14. The only casualty of his voyage was a crewman named John Norton who was stoned to death by the natives of Tofua, the first island they tried to land on.

At Tofua (Bligh spelled it "Tofoa"), Bligh and eighteen loyalists sought refuge in a cave in order to augment their meager provisions. In the March 1968 issue of the "National Geographic Magazine", Luis Marden claimed to have found this cave as well as the grave of John Norton. Both findings were later disproved by Bengt Danielsson (who had been a member of the 1947 Kon-Tiki expedition) in the June 1985 issue of the "Pacific Islands Monthly". Danielsson identified Bligh's cave as lying on the sheltered north-west coast, where Bligh identified it; Marden's cave lies on the exposed south-east coast. Additionally, Danielsson thought it highly unlikely that the Tofuans would have allotted any grave site to Norton, or that the grave, if allotted, would have been preserved for two centuries.

References

* [http://vulcan.wr.usgs.gov/Volcanoes/Tonga/description_tonga_volcanoes.html United States Geological Survey]
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* [http://library.puc.edu/pitcairn/bounty/encyclopedia.shtml Pitcairn Islands Study Center]