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Volcanism Of New Zealand
The volcanism of New Zealand has been responsible for many of the country's geographical features, especially in the North Island and the country's outlying islands. While the land's volcanism dates back to before the Zealandia microcontinent rifted away from Gondwana 60–130 million years ago, activity continues today with minor eruptions occurring every few years. This recent activity is primarily due to the country's position on the boundary between the Indo-Australian and Pacific Plates, a part of the Pacific Ring of Fire, and particularly the subduction of the Pacific Plate under the Indo-Australian Plate. New Zealand's rocks record examples of almost every kind of volcanism observed on Earth, including some of the world's largest eruptions in geologically recent times. None of the South Island's volcanoes are active. Major eruptions New Zealand has been the site of many large explosive eruptions during the last two million years, including several of supervolcan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
White Island Main Vent
White is the lightness, lightest color and is achromatic (having no colorfulness, chroma). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully (or almost fully) diffuse reflection, reflect and scattering, scatter all the visible spectrum, visible wavelengths of light. White on television and computer screens is created by a mixture of red, blue, and green light. The color white can be given with white pigments, especially titanium dioxide. In ancient Egypt and ancient Rome, priestesses wore white as a symbol of purity, and Romans wore white togas as symbols of citizenship. In the Middle Ages and Renaissance a white unicorn symbolized chastity, and a white lamb sacrifice and purity. It was the royal color of the kings of France as well as the flag of Bourbon Restoration in France, monarchist France from 1815 to July Revolution, 1830, and of the White movement, monarchist movement that opposed the Bolsheviks during the Ru ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Macauley Island
Macauley Island is a volcanic island in New Zealand's Kermadec Islands, approximately halfway between New Zealand's North Island and Tonga in the southwest Pacific Ocean. It is part of a larger submarine volcano that features a wide underwater caldera northwest of Macauley Island. Two islets, Haszard Island and Newcome Rock, lie east offshore of Macauley Island. The island is mostly surrounded by high cliffs that make accessing it difficult; the inland parts are mostly gently sloping terrain covered with ferns and grasses. The island was formed during several volcanic episodes that produced mainly basaltic rocks as lava flows. During the Holocene, a large explosive eruption produced the Sandy Bay Tephra; this eruption may have had a volume of more than and the Macauley caldera might have formed during that occasion. Later, the Haszard Formation built most of the current surface of Macauley Island. Two uncertain eruptions took place during the 19th century offshore Macaule ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chatham Islands
The Chatham Islands ( ; Moriori language, Moriori: , 'Misty Sun'; ) are an archipelago in the Pacific Ocean about east of New Zealand's South Island, administered as part of New Zealand, and consisting of about 10 islands within an approximate radius, the largest of which are Chatham Island and Pitt Island, Pitt Island (''Rangiauria''). They include New Zealand's easternmost point, the Forty-Fours. Some of the islands, formerly cleared for farming, are now preserved as Protected areas of New Zealand, nature reserves to conservation in New Zealand, conserve some of the unique flora and fauna. The islands were uninhabited when the Moriori people arrived around 1500 CE and developed Nunuku-whenua, a peaceful way of life. In 1835, members of the Ngāti Mutunga and Ngāti Tama Māori iwi from the North Island of New Zealand invaded the islands and Moriori genocide, nearly exterminated the Moriori, slavery, enslaving the survivors. In the period of European colonisation, the New ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ash Fall
Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to refer to all explosive eruption products (correctly referred to as '' tephra''), including particles larger than 2 mm. Volcanic ash is formed during explosive volcanic eruptions when dissolved gases in magma expand and escape violently into the atmosphere. The force of the gases shatters the magma and propels it into the atmosphere where it solidifies into fragments of volcanic rock and glass. Ash is also produced when magma comes into contact with water during phreatomagmatic eruptions, causing the water to explosively flash to steam leading to shattering of magma. Once in the air, ash is transported by wind up to thousands of kilometres away. Due to its wide dispersal, ash can have a number of impacts on society, including animal an ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tephra
Tephra is fragmental material produced by a Volcano, volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, they remain as tephra unless hot enough to fuse into pyroclastic rock or tuff. When a volcano explodes, it releases a variety of tephra including ash, cinders, and blocks. These layers settle on the land and, over time, sedimentation occurs incorporating these tephra layers into the geologic record. Tephrochronology is a geochronological technique that uses discrete layers of tephra—volcanic ash from a single eruption—to create a chronological framework in which Paleoecology, paleoenvironmental or Archaeology, archaeological records can be placed. Often, when a volcano explodes, biological organisms are killed and their remains are buried within the tephra layer. These fossils are later dated by scientists to determine the age of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanic Explosivity Index
The volcanic explosivity index (VEI) is a scale used to measure the size of explosive volcanic eruptions. It was devised by Christopher G. Newhall of the United States Geological Survey and Stephen Self in 1982. Volume of products, eruption cloud height, and qualitative observations (using terms ranging from "gentle" to "mega-colossal") are used to determine the explosivity value. The scale is open-ended with the largest eruptions in history given a magnitude of 8. A value of 0 is given for non-explosive eruptions, defined as less than of tephra ejected; and 8 representing a supervolcanic eruption that can eject (240 cubic miles) of tephra and have a cloud column height of over . The scale is logarithmic, with each interval on the scale representing a tenfold increase in observed ejecta criteria, with the exception of between VEI-0, VEI-1 and VEI-2. Classification With indices running from 0 to 8, the VEI associated with an eruption is dependent on how much volcanic materia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oruanui Eruption
The Oruanui eruption (also known as the Kawakawa eruption or Kawakawa/Oruanui event) of Taupō Volcano in New Zealand around 25,700 years before present was the world's most recent supereruption, and its largest phreatomagmatic eruption characterised to date. Geography At the time of the eruption, the sea level was much lower than at present, and for over 100,000 years the Taupō Volcano had been mainly under Lake Huka, a larger lake than the present Lake Taupō. Lake Huka was destroyed in the eruption, and other features of the local geography were changed significantly as outlined below. Eruption With a Volcanic Explosivity Index of 8, it is one of the largest eruptions ever to occur in New Zealand and the most recent supereruption. It occurred years BP in the Late Pleistocene. It generated approximately of pyroclastic fall deposits, of pyroclastic density current (PDC) deposits (mostly ignimbrite), and of primary intracaldera material, equivalent to of rhyolitic m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caldera
A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the structural integrity of such a chamber, greatly diminishing its capacity to support its own roof and any substrate or rock resting above. The ground surface then collapses into the emptied or partially emptied magma chamber, leaving a large depression at the surface (from one to dozens of kilometers in diameter). Although sometimes described as a Volcanic crater, crater, the feature is actually a type of sinkhole, as it is formed through subsidence and collapse rather than an explosion or impact. Compared to the thousands of volcanic eruptions that occur over the course of a century, the formation of a caldera is a rare event, occurring only a few times within a given window of 100 years. Only eight caldera-forming collapses are known to have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haroharo Caldera
The Haroharo Caldera (Haroharo volcanic complex) is a postulated volcanic feature in Taupō Volcanic Zone of the North Island, New Zealand within the larger and older Ōkataina Caldera. Since 2010 further studies have tended to use the terms Haroharo vent alignment, Utu Caldera, Matahina Caldera, Rotoiti Caldera and a postulated Kawerau Caldera to the features assigned to it. However the name is used in the peer reviewed literature to summarise and group these features based on gravitational and magnetic features. Geography In the north the Haroharo Caldera has been mapped as extending from the eastern half of Lake Rotoiti to the western border of Lake Rotomā. Its southern extent was defined by the Tarawera volcano. A recent analysis is consistent with the south western structural boundary of the older single event caldera's being in the eastern portions of Lake Tarawera. Both the Ōkāreka Embayment and the Tarawera Volcanic Complex are adjacent, so many, especially ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rotorua Caldera
The Rotorua Caldera is a large rhyolitic caldera that is filled by Lake Rotorua. It was formed by an eruption 240,000 years ago that produced extensive Pyroclastic rock, pyroclastic deposits. Smaller eruptions have occurred in the caldera since, the most recent less than 25,000 years ago. It is one of several large volcanoes in the Taupō Volcanic Zone on the North Island of New Zealand. Geography The major regional settlement of Rotorua city is located in the caldera. There is geothermal activity in the city, and the geothermal areas of Tikitere and Whakarewarewa are associated with the caldera. These areas are still associated with small hydrothermal eruptions. Geology Eruption history The caldera was formed in a single event paired List of large volcanic eruptions, major eruption, lasting only weeks, that is now dated to 240,000 ± 11,000 years ago. It ejected more than of rhyolitic Mamaku ignimbrite giving it a Volcanic Explosivity Index of 7. The eruption has been reinte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
