| Tofua Caldera | |
|---|---|
Tofua Island (lower left) and neighbouring Kao Island, Tonga, Pacific Ocean |
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| Elevation | 515 m (1,690 ft) |
| Listing | List of volcanoes in Tonga |
| Location | |
| Location | Tonga Islands, Tonga |
| Geology | |
| Type | Volcanic caldera |
| Last eruption | 2009 |
Tofua Caldera, in Tonga, is the summit caldera of a steep-sided composite cone that forms Tofua Island. Tofua Island is in Tonga's Ha'apai island group. 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 with 500 m (1,600 ft) depth occupies most of the remainder.[1]
Most historical eruptions have been small explosions from Lofia cone along the northern caldera rim. The eruptions of 1958-59 caused most of the islanders to evacuate for a year or more.
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Tofua has a population of about fifty. They are there primarily to grow kava (Piper methysticum) for export to Tongatapu.
The Mutiny on the Bounty (1789) took place about 30 nautical miles (56 km; 35 mi) 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 (6,701 km; 4,164 mi). 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.
In the early seventies a group of eight Tongan fishermen were shipwrecked on Ata island and then survived for 18 months before being rescued by an Austrailian millionaire who, upon visiting the island out of curiosity, came upon the naked bearded men when scanning the islands coast through his binoculars. It took the men eight months to create fire and the flame was maintained through wind, rain and gale for the subsequent 10 months with each taking shifts to protect it. Prior to making fire they lived primarily off of coconuts and raw seafood. After being documented by ABC news in America the story faded away but many of the men involved still live on Lifuka island.
E. W. Gifford, recording Tongan myths and tales in the 1920s, documented this explanation for Tofua's caldera and the creation of Kao Island to the north:
"Three deities from Samoa, Tuvuvata, Sisi, and Faingaa, conspired to steal Tofua. So they came and tore up the high mountain by its very roots and its place was taken by a large lake. This enraged the Tongan gods very much and one of them, Tafakula, essayed to stop the thieves. He stood on the island of Luahako and bent over so as to show his anus. It shone so brilliantly that the Samoan deities were struck with fear, thinking that the sun was rising and that their dastardly work was about to be revealed. Hence, they dropped the mountain and fled to Samoa. The mountain became the island of Kao."[2]