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Hawaiian Eruption
A Hawaiian eruption
Hawaiian eruption
is a type of volcanic eruption where lava flows from the vent in a relatively gentle, low level eruption; it is so named because it is characteristic of Hawaiian volcanoes. Typically they are effusive eruptions, with basaltic magmas of low viscosity, low content of gases, and high temperature at the vent. Very little amounts of volcanic ash are produced
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Ash Plume
An eruption column is a cloud of hot volcanic ash suspended in volcanic gas emitted during an explosive volcanic eruption. The ash forms a column that may rise many kilometres into the air above the vent of the volcano. In the most explosive eruptions, the eruption column may rise over 40 km, penetrating the stratosphere. Stratospheric injection of aerosols by volcanoes is a major cause of short-term climate change. A common occurrence in explosive eruptions is for column collapse to occur. In this case, the eruption column is too dense to be lifted high into the air by air convection, and instead falls down the flanks of the volcano to form a pyroclastic flow or surge
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Skjaldbreiður
Skjaldbreiður, meaning the broad shield in Icelandic, is an Icelandic lava shield formed in one huge and protracted eruption roughly 9,000 years ago[citation needed]. The extensive lava fields which were produced by this eruption, flowed southwards, and formed the basin of Þingvallavatn, Iceland's largest lake, and Þingvellir, the "Parliament Plains" where the Icelandic national assembly, the Alþing was founded in 930. The volcano summit is at 1,060 metres, and its crater measures roughly 300 metres in diameter. Straddling the Mid-Atlantic ridge, the lava fields from Skjaldbreiður have been torn and twisted over the millennia, forming a multitude of fissures and rifts inside the Þingvellir
Þingvellir
National Park, the best known of which are Silfra, Almannagjá, Hrafnagjá and Flosagjá. Gallery[edit] Skjaldbreiður
Skjaldbreiður
crater in snow.References[edit]Scarth, Alwyn; Tanguy, Jean-Claude (2001)
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Surtsey
Surtsey
Surtsey
("Surtr's island" in Icelandic, Icelandic pronunciation: ​[ˈsʏr̥tsei]) is a volcanic island located in the Vestmannaeyjar
Vestmannaeyjar
archipelago off the southern coast of Iceland. At 63°18′11″N 20°36′18″W / 63.303°N 20.605°W / 63.303; -20.605Coordinates: 63°18′11″N 20°36′18″W / 63.303°N 20.605°W / 63.303; -20.605, Surtsey
Surtsey
is the southernmost point of Iceland[1]. It was formed in a volcanic eruption which began 130 metres (426 ft) below sea level, and reached the surface on 14 November 1963. The eruption lasted until 5 June 1967, when the island reached its maximum size of 2.7 km2 (1.0 sq mi)
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Fissure Vent
A fissure vent, also known as a volcanic fissure or eruption fissure, is a linear volcanic vent through which lava erupts, usually without any explosive activity. The vent is often a few meters wide and may be many kilometers long. Fissure vents can cause large flood basalts which run first in lava channels and later in lava tubes. After some time the eruption builds up spatter cones and may concentrate on one or some of them. Small fissure vents may not be easily discernible from the air, but the crater rows (see Laki) or the canyons (see Eldgjá) built up by some of them are. The dikes that feed fissures reach the surface from depths of a few kilometers and connect them to deeper magma reservoirs, often under volcanic centers. Fissures are usually found in or along rifts and rift zones, such as Iceland
Iceland
and the East African Rift
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Volcanic Crater
A volcanic crater is a roughly circular depression in the ground caused by volcanic activity.[1] It is typically a bowl-shaped feature within which occurs a vent or vents. During volcanic eruptions, molten magma and volcanic gases rise from an underground magma chamber, through a tube-shaped conduit, until they reach the crater's vent, from where the gases escape into the atmosphere and the magma is erupted as lava. A volcanic crater can be of large dimensions, and sometimes of great depth. During certain types of explosive eruptions, a volcano's magma chamber may empty enough for an area above it to subside, forming a type of larger depression known as a caldera. Geomorphology[edit] In most volcanoes, the crater is situated at the top of a mountain formed from the erupted volcanic deposits such as lava flows and tephra. Volcanoes that terminate in such a summit crater are usually of a conical form
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Rift Zone
A rift zone is a feature of some volcanoes, especially shield volcanoes, in which a linear series of cracks (or rifts) develops in a volcanic edifice, typically forming into two or three well-defined regions along the flanks of the vent.[1] Believed to be primarily caused by internal and gravitational stresses generated by magma emplacement within and across various regions of the volcano, rift zones allow the intrusion of magmatic dykes into the slopes of the volcano itself
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Mount Mihara
Mount Mihara
Mount Mihara
(三原山, Mihara-yama) is an active volcano on the Japanese isle of Izu Ōshima. Although the volcano is predominantly basaltic, major eruptions have occurred at intervals of 100–150 years.[1] Mount Mihara's major eruption in 1986 saw lava fountains up to 1.6 kilometres (1.0 mi) high. The eruption had a Volcanic Explosivity Index of 3, and involved a central vent eruption, radial fissure eruption, explosive eruption, lava flows, and a lava lake eruption. There was also a 16 km high subplinian plume
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Izu Ōshima
Izu Ōshima
Izu Ōshima
(伊豆大島, Izu-ōshima) is an inhabited volcanic island in the Izu archipelago in the Philippine Sea, approximately 120 kilometres (75 mi) southeast of Honshu, Japan, 22 km (14 mi) east of the Izu Peninsula
Izu Peninsula
and 36 km (22 mi) southwest of Bōsō Peninsula.[1] As with the other islands in the Izu Island group, Miyake-jima forms part of the Fuji-Hakone-Izu National Park
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Japan
Japan
Japan
(Japanese: 日本, Nippon [ɲippoꜜɴ] (listen) or Nihon [ɲihoꜜɴ] (listen); formally 日本国, Nippon-koku or Nihon-koku, lit. 'State of Japan') is an island country in East Asia. Located in the Pacific Ocean, it lies off the eastern coast of the Asian continent
Asian continent
and stretches from the Sea of Okhotsk
Sea of Okhotsk
in the north to the East China Sea
East China Sea
and the Philippine Sea
Philippine Sea
in the south. The kanji that make up Japan's name mean 'sun origin', and it is often called the "Land of the Rising Sun". Japan
Japan
is the world's 4th largest island country and encompasses about 6,852 islands
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Iceland
Iceland
Iceland
(/ˈaɪslənd/ ( listen); Icelandic: Ísland, pronounced [ˈistlant])[7] is a Nordic island country in the North Atlantic, with a population of 348,580 and an area of 103,000 km2 (40,000 sq mi), making it the most sparsely populated country in Europe.[8] The capital and largest city is Reykjavík. Reykjavík
Reykjavík
and the surrounding areas in the southwest of the country are home to over two-thirds of the population. Iceland
Iceland
is volcanically and geologically active. The interior consists of a plateau characterised by sand and lava fields, mountains, and glaciers, while many glacial rivers flow to the sea through the lowlands. Iceland
Iceland
is warmed by the Gulf Stream
Gulf Stream
and has a temperate climate, despite a high latitude just outside the Arctic
Arctic
Circle
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National Geographic Society
The National Geographic
National Geographic
Society (NGS), headquartered in Washington, D.C., United States, is one of the largest non-profit scientific and educational institutions in the world. Founded in 1888, its interests include geography, archaeology and natural science, the promotion of environmental and historical conservation, and the study of world culture and history. The National Geographic
National Geographic
Society’s logo is a yellow portrait frame – rectangular in shape – which appears on the margins surrounding the front covers of its magazines and as its television channel logo
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Tholeiite
The tholeiitic magma series, named after the German municipality of Tholey, is one of two main magma series in igneous rocks, the other being the calc-alkaline series. A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic magma into a more evolved, silica rich end member. The International Union of Geological Sciences recommends that tholeiitic basalt be used in preference to the term "tholeiite" (Le Maitre and others, 2002).Contents1 Geochemical characterization 2 Petrography 3 Geologic context 4 See also 5 ReferencesGeochemical characterization[edit]This is an AFM diagram, a ternary diagram showing the relative proportions of the oxides of Na2O + K2O (A), FeO + Fe2O3 (F), and MgO (M)
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Nephelinite
Nephelinite
Nephelinite
is a fine-grained or aphanitic igneous rock made up almost entirely of nepheline and clinopyroxene (variety augite). If olivine is present, the rock may be classified as an olivine nephelinite. Nephelinite
Nephelinite
is dark in color and may resemble basalt in hand specimen. However, basalt consists mostly of clinopyroxene (augite) and calcic plagioclase. Basalt, alkali basalt, basanite, tephritic nephelinite, and nephelinite differ partly in the relative proportions of plagioclase and nepheline. Alkali basalt may contain minor nepheline and does contain nepheline in its CIPW normative mineralogy. A critical ratio in the classification of these rocks is the ratio nepheline/(nepheline plus plagioclase). Basanite
Basanite
has a value of this ratio between 0.1 and 0.6 and also contains more than 10% olivine. Tephritic nephelinite has a value between 0.6 and 0.9
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Mantle Plume
A mantle plume is an upwelling of abnormally hot rock within the Earth's mantle, first proposed by J. Tuzo Wilson
J. Tuzo Wilson
in 1963.[2] As the heads of mantle plumes can partly melt when they reach shallow depths, they are often invoked as the cause of volcanic hotspots, such as Hawaii or Iceland, and flood basalts such as the Deccan and Siberian traps. Some such volcanic regions lie far from tectonic plate boundaries, while others represent unusually large-volume volcanism near plate boundaries or in large igneous provinces. A mantle plume is posited to exist where hot rock nucleates at the core-mantle boundary and rises through the Earth's mantle becoming a diapir in the Earth's crust.[3] The currently active volcanic centers are known as hotspots
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Tourists
Tourism
Tourism
is travel for pleasure or business; also the theory and practice of touring, the business of attracting, accommodating, and entertaining tourists, and the business of operating tours.[1] Tourism may be international, or within the traveller's country. The World Tourism
Tourism
Organization defines tourism more generally, in terms which go "beyond the common perception of tourism as being limited to holiday activity only", as people "traveling to and staying in places outside their usual environment for not more than one consecutive year for leisure, business and other purposes".[2] Tourism
Tourism
can be domestic or international, and international tourism has both incoming and outgoing implications on a country's balance of payments
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