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Tofua Volcanic Arc
Tofua is a volcanic island in Tonga. Located in the Haʻapai island group, it is a steep-sided composite cone with a summit caldera. It is part of the highly active Kermadec-Tonga subduction zone and its associated volcanic arc, which extends from New Zealand north-northeast to Fiji, and is formed by the subduction of the Pacific Plate under the Indo-Australian Plate. It lies about above a very active seismic zone.Ewart, A.; Bryan, W.B.; and Gill, J.B. "Mineralogy and Geochemistry of the Younger Volcanic Islands of Tonga, S.W. Pacific." ''Journal of Petrology.'' 14:3 (1973). It is connected to the nearby island of Kao by a submarine ridge. The island is a national park. Geography and geology The island is oval, measuring approximately 80 square kilometers. Its sides rise steeply to the rim of the caldera, which is partially filled by a volcanic crater lake with a depth of . The caldera was formed by a major eruption around 1,000 years BP, which left deposits up to thic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kao (island)
Kao is an island and stratovolcano in the Haʻapai island group of Tonga. It lies about north of Tofua island and reaches above sea level, the highest point in Tonga. The date of its last eruption is unknown. Although Kao does not display fresh-looking lava flows, it is likely very recent in origin due to the absence of deep gullies or high sea cliffs. The slopes of the island rise at angles exceeding 35 degrees to the summit, which has a series of small volcanic craters. The last reported eruption was on July 10, 1847. The best access to Kao is by small boat on the south coast of the island, although heavy swell can make this treacherous and a skilled boat coxswain is required. There are no permanent paths to the summit. Small areas on the lower slopes are cultivated by kava growers. The island is densely jungled on its lower flanks, interspersed with thick chest-height ferns that are virtually impassable to all but the most determined trekkers armed with machetes and a good ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ignimbrite
Ignimbrite is a type of volcanic rock, consisting of hardened tuff. Ignimbrites form from the deposits of pyroclastic flows, which are a hot suspension of particles and gases flowing rapidly from a volcano, driven by being denser than the surrounding atmosphere. New Zealand geologist Patrick Marshall (1869-1950) coined the term ''ignimbrite'' from the Latin ''igni-'' [fire] and ''imbri-'' [rain]. Ignimbrites are made of a very poorly sorted mixture of volcanic ash (or tuff when Lithification, lithified) and pumice lapilli, commonly with scattered lithic fragments. The ash is composed of glass shards and crystal fragments. Ignimbrites may be loose and unconsolidated, or lithified (solidified) rock called lapilli-tuff. Near the volcanic source, ignimbrites often contain thick accumulations of lithic blocks, and distally, many show meter-thick accumulations of rounded cobbles of pumice. Ignimbrites may be white, grey, pink, beige, brown, or black depending on their composition and d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Backstaff
The backstaff is a navigational instrument that was used to measure the altitude of a celestial body, in particular the Sun or Moon. When observing the Sun, users kept the Sun to their back (hence the name) and observed the shadow cast by the upper vane on a horizon vane. It was invented by the English navigator John Davis, who described it in his book ''Seaman's Secrets'' in 1594. Types of backstaffs Backstaff is the name given to any instrument that measures the altitude of the sun by the projection of a shadow. It appears that the idea for measuring the sun's altitude using back observations originated with Thomas Harriot. Many types of instruments evolved from the cross-staff that can be classified as backstaves. Only the Davis quadrant remains dominant in the history of navigation instruments. Indeed, the Davis quadrant is essentially synonymous with backstaff. However, Davis was neither the first nor the last to design such an instrument and others are considered here ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Timor
Timor is an island at the southern end of Maritime Southeast Asia, in the north of the Timor Sea. The island is East Timor–Indonesia border, divided between the sovereign states of East Timor on the eastern part and Indonesia on the western part. The Indonesian part, also known as West Timor, constitutes part of the Provinces of Indonesia, province of East Nusa Tenggara. Within West Timor lies an exclave of East Timor called Oecusse District. The island covers an area of . The name is a variant of ''timur'', Malay language, Malay for "east"; it is so called because it lies at the eastern end of the Lesser Sunda Islands. Mainland Australia is less than 500 km away, separated by the Timor Sea. Language, ethnic groups and religion Anthropologists identify eleven distinct Ethnolinguistic group, ethno-linguistic groups in Timor. The largest are the Atoni of western Timor and the Tetum of central and eastern Timor. Most indigenous Timorese languages belong to the Timorâ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kupang
Kupang ( id, Kota Kupang, ), formerly known as Koepang, is the capital of the Indonesian province of East Nusa Tenggara. At the 2020 C ensus, it had a population of 442,758; the official estimate as at mid 2021 was 455,850. It is the largest city and port on the island of Timor, and is a part of the Timor Leste-Indonesia-Australia Growth Triangle free trade zone. Geographically, Kupang is the southernmost city in Indonesia. History Early history and Portuguese domination Kupang was an important port and trading post during the Portuguese and Dutch colonial eras. There are still ruins and remnants of the colonial presence in the city. Representatives of the Dutch East India Company (VOC) first encountered Kupang in 1613 after having conquered the Portuguese fort on the island of Solor. At this time the area of the city was governed by a Raja of the Helong tribe, who claimed descent from the island of Ceram in the Maluku archipelago. Kupang occupied an ideal strategic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dutch East India Company
The United East India Company ( nl, Verenigde Oostindische Compagnie, the VOC) was a chartered company established on the 20th March 1602 by the States General of the Netherlands amalgamating existing companies into the first joint-stock company in the world, granting it a 21-year monopoly to carry out trade activities in Asia. Shares in the company could be bought by any resident of the United Provinces and then subsequently bought and sold in open-air secondary markets (one of which became the Amsterdam Stock Exchange). It is sometimes considered to have been the first multinational corporation. It was a powerful company, possessing quasi-governmental powers, including the ability to wage war, imprison and execute convicts, negotiate treaties, strike its own coins, and establish colonies. They are also known for their international slave trade. Statistically, the VOC eclipsed all of its rivals in the Asia trade. Between 1602 and 1796 the VOC sent almost a million Eur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Bligh
Vice-Admiral William Bligh (9 September 1754 – 7 December 1817) was an officer of the Royal Navy and a colonial administrator. The mutiny on the HMS ''Bounty'' occurred in 1789 when the ship was under his command; after being set adrift in ''Bounty''s launch by the mutineers, Bligh and his loyal men all reached Timor alive, after a journey of . Bligh's logbooks documenting the mutiny were inscribed on the UNESCO Australian Memory of the World register on 26 February 2021. Seventeen years after the ''Bounty'' mutiny, on 13 August 1806, he was appointed Governor of New South Wales in Australia, with orders to clean up the corrupt rum trade of the New South Wales Corps. His actions directed against the trade resulted in the so-called Rum Rebellion, during which Bligh was placed under arrest on 26 January 1808 by the New South Wales Corps and deposed from his command, an act which the British Foreign Office later declared to be illegal. He died in London on 7 December 1817. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mutiny On The Bounty
The mutiny on the Royal Navy vessel occurred in the South Pacific Ocean on 28 April 1789. Disaffected crewmen, led by acting-Lieutenant Fletcher Christian, seized control of the ship from their captain, Lieutenant William Bligh, and set him and eighteen loyalists adrift in the ship's open launch. The mutineers variously settled on Tahiti or on Pitcairn Island. Bligh navigated more than in the launch to reach safety, and began the process of bringing the mutineers to justice. ''Bounty'' had left England in 1787 on a mission to collect and transport breadfruit plants from Tahiti to the West Indies. A five-month layover in Tahiti, during which many of the men lived ashore and formed relationships with native Polynesians, led those men to be less amenable to military discipline. Relations between Bligh and his crew deteriorated after he allegedly began handing out increasingly harsh punishments, criticism, and abuse, Christian being a particular target. After three weeks ba ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Captain Cook
James Cook (7 November 1728 Old Style date: 27 October – 14 February 1779) was a British explorer, navigator, cartographer, and captain in the British Royal Navy, famous for his three voyages between 1768 and 1779 in the Pacific Ocean and to New Zealand and Australia in particular. He made detailed maps of Newfoundland prior to making three voyages to the Pacific, during which he achieved the first recorded European contact with the eastern coastline of Australia and the Hawaiian Islands, and the first recorded circumnavigation of New Zealand. Cook joined the British merchant navy as a teenager and joined the Royal Navy in 1755. He saw action in the Seven Years' War and subsequently surveyed and mapped much of the entrance to the St. Lawrence River during the siege of Quebec, which brought him to the attention of the Admiralty and the Royal Society. This acclaim came at a crucial moment for the direction of British overseas exploration, and it led to his commission in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fumarole
A fumarole (or fumerole) is a vent in the surface of the Earth or other rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volcanic activity, but fumarole activity can also precede a volcanic eruption and has been used for eruption prediction. Most fumaroles die down within a few days or weeks of the end of an eruption, but a few are persistent, lasting for decades or longer. An area containing fumaroles is known as a fumarole field. The predominant vapor emitted by fumaroles is steam, formed by the circulation of groundwater through heated rock. This is typically accompanied by volcanic gases given off by magma cooling deep below the surface. These volcanic gases include sulfur compounds, such as various sulfur oxides and hydrogen sulfide, and sometimes hydrogen chloride, hydrogen fluoride, and other gases. A fumarole that emits significant sulfur compounds is some ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dacite
Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. It is composed predominantly of plagioclase feldspar and quartz. Dacite is relatively common, occurring in many tectonic settings. It is associated with andesite and rhyolite as part of the subalkaline volcanic rock, subalkaline tholeiite, tholeiitic and calc-alkaline magma series. Composition Dacite consists mostly of plagioclase feldspar and quartz with biotite, hornblende, and pyroxene (augite or enstatite). The quartz appears as rounded, corroded phenocrysts, or as an element of the ground-mass. The plagioclase in dacite ranges from oligoclase to andesine and labradorite. Sanidine occurs, although in small proportions, in some dacites, and when abundant gives rise to rocks that form rhyodacite, transitions to the rhyolites. The rel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Andesite
Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende. Andesite is the extrusive equivalent of plutonic diorite. Characteristic of subduction zones, andesite represents the dominant rock type in island arcs. The average composition of the continental crust is andesitic. Along with basalts, andesites are a component of the Martian crust. The name ''andesite'' is derived from the Andes mountain range, where this rock type is found in abundance. It was first applied by Christian Leopold von Buch in 1826. Description Andesite is an aphanitic (fine-grained) igneous rock that is intermediate in its content of silica and low in alkali metals. It has less than 20% quartz and 10% feldspathoid by volume, with at least 65% of the fe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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