Tofua Caldera, in Tonga
Tonga, officially the Kingdom of Tonga , is a state and an archipelago in the South Pacific Ocean, comprising 176 islands scattered over of ocean in the South Pacific...

, is the summit caldera
A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...

 of a steep-sided composite cone that forms Tofua Island. Tofua Island is in Tonga's Ha'apai
Haapai is a group of islands, islets, reefs and shoals in the central part of the Kingdom of Tonga, with the Tongatapu group to the south and the Vavau group to the north. Seventeen of the Haapai islands are populated....

 island group. Pre-caldera activity is recorded by a sequence of pyroclastic deposits and lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...

s constituting the older cone, followed on the northern part of the island by froth lavas or welded and unwelded ignimbrite
An ignimbrite is the deposit of a pyroclastic density current, or pyroclastic flow, a hot suspension of particles and gases that flows rapidly from a volcano, driven by a greater density than the surrounding atmosphere....

. Following caldera collapse, lavas were erupted from the northern part of the island and the caldera-rim fissure zone, scoria
Scoria is a volcanic rock containing many holes or vesicles. It is most generally dark in color , and basaltic or andesitic in composition. Scoria is relatively low in mass as a result of its numerous macroscopic ellipsoidal vesicles, but in contrast to pumice, all scoria has a specific gravity...

 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 andesite
Andesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite,...

s and andesites, plus occasional dacite
Dacite is an igneous, volcanic rock. It has an aphanitic to porphyritic texture and is intermediate in composition between andesite and rhyolite. The relative proportions of feldspars and quartz in dacite, and in many other volcanic rocks, are illustrated in the QAPF diagram...

 flows within the older cone. A postcaldera cone with fumarolic
A fumarole is an opening in a planet's crust, often in the neighborhood of volcanoes, which emits steam and gases such as carbon dioxide, sulfur dioxide, hydrochloric acid, and hydrogen sulfide. The steam is created when superheated water turns to steam as its pressure drops when it emerges from...

 activity (Lofia) is situated in the northern part of the caldera; a crater lake
Crater lake
A crater lake is a lake that forms in a volcanic crater or caldera, such as a maar; less commonly and with lower association to the term a lake may form in an impact crater caused by a meteorite. Sometimes lakes which form inside calderas are called caldera lakes, but often this distinction is not...

 with 500 m (1,640.4 ft) 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 the islanders to evacuate for a year or more.

Tofua Island

Tofua has a population of about fifty. They are there primarily to grow kava
Kava or kava-kava is a crop of the western Pacific....

 (Piper methysticum) for export to Tongatapu
Tongatapu is the main island of the Kingdom of Tonga and the location of its capital Nukualofa. It is located in Tonga's southern island group, to which it gives its name, and is the country's most populous island, with approximately 71,260 residents , 70.5% of the national population...


Tofua in History

The Mutiny on the Bounty
Mutiny on the Bounty
The mutiny on the Bounty was a mutiny that occurred aboard the British Royal Navy ship HMS Bounty on 28 April 1789, and has been commemorated by several books, films, and popular songs, many of which take considerable liberties with the facts. The mutiny was led by Fletcher Christian against the...

 (1789) took place about 30 nmi (55.6 km; 34.5 mi) from Tofua. Captain William Bligh
William Bligh
Vice Admiral William Bligh FRS RN was an officer of the British Royal Navy and a colonial administrator. A notorious mutiny occurred during his command of HMAV Bounty in 1789; Bligh and his loyal men made a remarkable voyage to Timor, after being set adrift in the Bounty's launch by the mutineers...

 navigated the overcrowded 23 feet (7 m) open launch on an epic 41-day voyage first to Tofua and then to Timor
Timor is an island at the southern end of Maritime Southeast Asia, north of the Timor Sea. It is divided between the independent state of East Timor, and West Timor, belonging to the Indonesian province of East Nusa Tenggara. The island's surface is 30,777 square kilometres...

 equipped only with a sextant
A sextant is an instrument used to measure the angle between any two visible objects. Its primary use is to determine the angle between a celestial object and the horizon which is known as the altitude. Making this measurement is known as sighting the object, shooting the object, or taking a sight...

 and a pocket watch
Pocket watch
A pocket watch is a watch that is made to be carried in a pocket, as opposed to a wristwatch, which is strapped to the wrist. They were the most common type of watch from their development in the 16th century until wristwatches became popular after World War I during which a transitional design,...

 -- no charts or compass. He recorded the distance as 3618 nmi (6,700.5 km; 4,163.5 mi). He passed through the difficult Torres Strait
Torres Strait
The Torres Strait is a body of water which lies between Australia and the Melanesian island of New Guinea. It is approximately wide at its narrowest extent. To the south is Cape York Peninsula, the northernmost continental extremity of the Australian state of Queensland...

 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
National Geographic Magazine
National Geographic, formerly the National Geographic Magazine, is the official journal of the National Geographic Society. It published its first issue in 1888, just nine months after the Society itself was founded...

, Luis Marden
Luis Marden
Luis Marden was an American photographer, explorer, writer, filmmaker, diver, navigator, and linguist who worked for National Geographic Magazine. He worked as a photographer and reporter before serving as chief of the National Geographic foreign editorial staff...

 claimed to have found this cave as well as the grave of John Norton. Both findings were later disproved by Bengt Danielsson
Bengt Danielsson
Bengt Emmerik Danielsson was an anthropologist and a crew member on the Kon-Tiki raft expedition from South America to French Polynesia in 1947. Danielsson was born in Sweden in 1921, obtained a Ph.D...

 (who had been a member of the 1947 Kon-Tiki
Kon-Tiki was the raft used by Norwegian explorer and writer Thor Heyerdahl in his 1947 expedition across the Pacific Ocean from South America to the Polynesian islands. It was named after the Inca sun god, Viracocha, for whom "Kon-Tiki" was said to be an old name...

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 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.

The Oral Tradition of Kao and Tofua

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."
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