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Whakatāne Graben
The Whakatāne Graben (also Whakatane Graben) is a predominantly normal faulting tectonic feature of the northeastern aspect of the young, modern Taupō Rift in New Zealand. At the coast it is widening by about /year. This very geologically active graben was the site of the 1987 Edgecumbe earthquake, which caused up to of land subsidence. The discontinuity in the Taupō Volcanic Zone's faults imposed by the highly active Ōkataina Volcanic Centre, geography and geology mean the graben is usually regarded as including the actively expanding and lowering region onshore extending towards the coast. Some scientists have limited the Whakatāne Graben to only the offshore continuation of the Taupō Rift. Geography The graben extends on shore from the west of the town of Kawerau to the coast at Matatā in the north and Whakatāne in the south. It is drained by the Tarawera River to the north and the Rangitaiki River to the south. The volcano of Putauaki (Mount Edgecumbe) is towar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Graben
In geology, a graben () is a depressed block of the crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German, meaning 'ditch' or 'trench'. The word was first used in the geologic context by Eduard Suess in 1883. The plural form is either ''graben'' or ''grabens''. Formation A graben is a valley with a distinct escarpment on each side caused by the displacement of a block of land downward. Graben often occur side by side with horsts. Horst and graben structures indicate tensional forces and crustal stretching. Graben are produced from parallel normal faults, where the displacement of the hanging wall is downward, while that of the footwall is upward. The faults typically dip toward the center of the graben from both sides. Horsts are parallel blocks that remain between graben; the bounding faults of a horst typically dip away from the center line of the horst. Single or multiple graben can produce a rift valley. Half-g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Putauaki
Putauaki ( mi, Pūtauaki; also known in English as Mount Edgecumbe) is a dacite volcanic cone in the Bay of Plenty Region of New Zealand. Located 50 km east of Rotorua and three kilometres east of Kawerau, it is the easternmost vent of the Okataina volcanic centre, within the Taupo Volcanic Zone. The mountain rises to 820 m above sea level, and is visible from the waters of the Bay of Plenty, 30 km to the north. Every year a King of the Mountain race is run on Putauaki as part of the international King of the Mountain series, and proceeds are donated to charity. History The last substantial volcanic eruption occurred around 300 BCE, producing a cubic kilometre of lava. Captain James Cook named the mountain "Mount Edgecumbe" on 2 November 1769, possibly in honour of John Edgecombe, the sergeant of marines on his vessel, the ''Endeavour''. The mountain's official name changed back to Putauaki in 1925. The New Zealand government took part of the mountain fro ... [...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] |
Tephra
Tephra is fragmental material produced by a 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. Tephrochronology is a geochronological technique that uses discrete layers of tephra—volcanic ash from a single eruption—to create a chronological framework in which paleoenvironmental or archaeological records can be placed. 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. 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 fossil and its place within the geolo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kawerau Power Station
The Kawerau Power Station is a 100-megawatt geothermal power plant located just outside the town of Kawerau in the Bay of Plenty Region of New Zealand. The power station is situated within the Kawerau geothermal field, which is part of the Taupo Volcanic Zone. Completed in July 2008 by Mighty River Power at a cost of NZ$300 million, the plant's capacity proved greater than expected. The station is the largest single generator geothermal plant in New Zealand. Energy production The Kawerau geothermal power station boosted the country's geothermal capacity by 25 percent and significantly increased local generation capacity in the Eastern Bay of Plenty. The plant meets approximately one third of residential and industrial demand in the region and provides cost certainty to local industry including Norske Skog Tasman. The station uses a single Fuji turbine and steam from geothermal bores. The two phase fluid is flashed/separated twice to produce high and low pressure steam to fee ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pleistocene
The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in 2009 by the International Union of Geological Sciences, the cutoff of the Pleistocene and the preceding Pliocene was regarded as being 1.806 million years Before Present (BP). Publications from earlier years may use either definition of the period. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology. The name is a combination of Ancient Greek grc, label=none, πλεῖστος, pleīstos, most and grc, label=none, καινός, kainós (latinized as ), 'new'. At the end of the preceding Pliocene, the previously isolated North and South American continents were joined by the Isthmus of Panama, causing Great American Interchang ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moutohora Island
Moutohora Island (previously known as Whale Island) ( mi, Moutohorā) is a small uninhabited island located off the Bay of Plenty coast of New Zealand's North Island, about north of the town of Whakatane. The island is a remnant of a complex volcano which has eroded, leaving two peaks. This is still an area of volcanic activity and there are hot springs on the island in Sulphur Valley, McEwans Bay, and Sulphur Bay. Name The Māori name, , is a contracted form of , meaning "Whale Island" or "Captured Whale". The spelling "Moutohorā " (with a macron) is sometimes also used in English, although the official name of the island omits it. The spelling "Motuhora" is also used. ( is the Māori name for the southern right whale.) History Numerous archaeological sites of both Māori and European origin have been recorded, including an extensive pa (fortified earthworks) site on Pa Hill and a number of house terraces and garden sites, middens (food refuse dumps), stone tool manufact ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Taupō Fault Belt
The Taupō Fault Belt contains many almost parallel active faults, and is located in the Taupō Rift of the central North Island of New Zealand geographically between Lake Taupō and the lakes of Rotorua, Tarawera, Rotomahana and Rerewhakaaitu. The potential active fault density is very high, with only separating the north-east to south-west orientated normal fault strands on detailed mapping of part of the belt. The Waikato River bisects the western region of the belt. Geology The northern Taupō Fault Belt is in the area also referred to as either, the Paeroa Graben or the Kapenga Graben, between the Horohoro Fault and the Paeroa Fault. Aligned with the orientation of the modern Taupō Rift are multiple north-north-east trending normal faults. These include the Ngakuru Fault to the east with the Ngakuru Graben between it and the Whirinaki Fault. Within the wide Ngakuru Graben are also to the west the Maleme Fault (Zone), which as a zone also contains the Mangaete/Lakeside F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhyolite
Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral assemblage is predominantly quartz, sanidine, and plagioclase. It is the extrusive equivalent to granite. Rhyolitic magma is extremely viscous, due to its high silica content. This favors explosive eruptions over effusive eruptions, so this type of magma is more often erupted as pyroclastic rock than as lava flows. Rhyolitic ash-flow tuffs are among the most voluminous of continental igneous rock formations. Rhyolitic tuff has been extensively used for construction. Obsidian, which is rhyolitic volcanic glass, has been used for tools from prehistoric times to the present day because it can be shaped to an extremely sharp edge. Rhyolitic pumice finds use as an abrasive, in concrete, and as a soil amendment. Description Rhyolite i ... [...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] |
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] |
Graywacke
Greywacke or graywacke (German ''grauwacke'', signifying a grey, earthy rock) is a variety of sandstone generally characterized by its hardness, dark color, and poorly sorted angular grains of quartz, feldspar, and small rock fragments or lithic fragments set in a compact, clay-fine matrix. It is a texturally immature sedimentary rock generally found in Paleozoic strata. The larger grains can be sand- to gravel-sized, and matrix materials generally constitute more than 15% of the rock by volume. The term "greywacke" can be confusing, since it can refer to either the immature (rock fragment) aspect of the rock or its fine-grained (clay) component. The origin of greywacke was unknown until turbidity currents and turbidites were understood, since, according to the normal laws of sedimentation, gravel, sand and mud should not be laid down together. Geologists now attribute its formation to submarine avalanches or strong turbidity currents. These actions churn sediment and cause mi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
