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North Island Volcanic Plateau
The North Island Volcanic Plateau (often called the Central Plateau and occasionally the Waimarino Plateau) is a volcanic plateau covering much of central North Island of New Zealand with volcanoes, lava plateaus, and crater lakes. It contains the Taupō Volcano, Taupō caldera complex, Ōkataina Caldera, Ōkataina caldera complex and Mount Tongariro, Tongariro Volcanic Centre resulting in it being currently the most frequently active and productive area of silicic volcanism on Earth. New Zealand is part of the Pacific Ring of Fire. Location and description The plateau is approximately east–west and the north–south distance is about . Extensive ignimbrite sheets spread east and west from the Central Taupō Volcanic Zone, centred on the huge active supervolcano, supervolcanic caldera of Lake Taupō, now the largest lake in New Zealand. This last erupted less than 2000 years ago. The volcanic area includes the three active peaks of Mount Tongariro, Mount Ngauruhoe, and M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanic Plateau
A volcanic plateau is a plateau produced by volcanic activity. There are two main types: lava plateaus and pyroclastic plateaus. Lava plateau Lava plateaus are formed by highly fluid basaltic lava during numerous successive eruptions through numerous vents without violent explosions (quiet eruptions). These eruptions are quiet because of the low viscosity of the lava and the small amount of trapped gases. The resulting sheet lava flows may be extruded from linear fissures or rifts or gigantic volcanic eruptions through multiple vents characteristic of the prehistoric era which produced giant flood basalts. Multiple successive and extensive lava flows cover the original landscape to eventually form a plateau, which may contain lava fields, cinder cones, shield volcanoes and other volcanic landforms. In some cases, a lava plateau may be part of a single volcano. An example is the massive Level Mountain shield volcano in northern British Columbia, Canada, which covers a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kaituna River
The Kaituna River is in the Bay of Plenty region of the North Island of New Zealand. It is the outflow from Lakes Rotorua and Rotoiti, and flows northwards for , emptying into the Bay of Plenty at Maketu. It was the subject of a claim concerning the effluent flowing down the river from Lake Rotorua, which resulted in movement to a land treatment system. The New Zealand Ministry for Culture and Heritage gives a translation of "eat eels" for ''Kaituna''. The upper section of the Kaituna, also referred to as Okere River, offers some of the best whitewater kayaking and rafting in the world, with the Okere Falls area containing the highest commercially rafted waterfall, , in the world. It is also famous for its trout fishing. Cultural claim During the 1970s Lake Rotorua was becoming eutrophic under heavy nutrient loadings, leading the Ministry of Works to propose diverting some sewage flow into the Kaituna River. Local iwi objected however, and filed a claim with the Waitangi T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rotorua
Rotorua () is a city in the Bay of Plenty region of New Zealand's North Island. It is sited on the southern shores of Lake Rotorua, from which it takes its name. It is the seat of the Rotorua Lakes District, a territorial authorities of New Zealand, territorial authority encompassing Rotorua and several other nearby towns. It has an estimated resident population of , making it the country's list of New Zealand urban areas by population, 13th largest urban area, and the Bay of Plenty's second-largest urban area behind Tauranga. Māori people, Māori first settled in Rotorua in the 14th century, and a thriving pā was established at Ohinemutu by the people who would become Ngāti Whakaue. The city became closely associated with conflict during the Musket Wars of the 1820s. Ohinemutu was invaded by a Ngāpuhi-led coalition in 1823, commanded by Hongi Hika and Pōmare I (Ngāpuhi), Pōmare I. In the 19th century early European settlers had an interest in developing Rotorua, due to i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mount Ngauruhoe
Mount Ngauruhoe () is a volcanic cone in New Zealand. It is the youngest vent in the Mount Tongariro, Tongariro stratovolcano complex on the Central Plateau, New Zealand, Central Plateau of the North Island and first erupted about 2,500 years ago. Although often regarded as a separate mountain, geologically, it is a secondary cone of Mount Tongariro. The volcano lies between the active volcanoes of Mount Tongariro to the north and Mount Ruapehu to the south, to the west of the Rangipo Desert and to the south of the southern shore of Lake Taupō. Etymology Before the initial mapping of the area introduced labelling confusion, the local Māori name for the cone was Tongariro, and its summit crater was known as Ngāuruhoe. The local Māori traditions state that the volcano was named by Ngātoro-i-rangi, an ancestor of the local Māori iwi, Ngāti Tūwharetoa. Ngātoro-i-rangi called volcanic fire from his homeland Hawaiki, which eventually emerged at Ngauruhoe. The name ... [...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] |
Supervolcano
A supervolcano is a volcano that has had an eruption with a volcanic explosivity index (VEI) of 8, the largest recorded value on the index. This means the volume of deposits for such an eruption is greater than . Supervolcanoes occur when magma in the mantle rises into the crust but is unable to break through it. Pressure builds in a large and growing magma pool until the crust is unable to contain the pressure and ruptures. This can occur at hotspots (for example, Yellowstone Caldera) or at subduction zones (for example, Toba). Large-volume supervolcanic eruptions are also often associated with large igneous provinces, which can cover huge areas with lava and volcanic ash. These can cause long-lasting climate change (such as the triggering of a small ice age) and threaten species with extinction. The Oruanui eruption of New Zealand's Taupō Volcano (about 25,600 years ago) was the world's most recent VEI-8 eruption. Terminology The term "supervolcano" was f ... [...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] |
Pacific Ring Of Fire
The Ring of Fire (also known as the Pacific Ring of Fire, the Rim of Fire, the Girdle of Fire or the Circum-Pacific belt) is a tectonic belt of volcanoes and earthquakes. It is about long and up to about wide, and surrounds most of the Pacific Ocean. The Ring of Fire contains between 750 and 915 active or dormant volcanoes, around two-thirds of the world total. The exact number of volcanoes within the Ring of Fire depends on which regions are included. About 90% of the world's earthquakes, including most of its largest, occur within the belt. The Ring of Fire is not a single geological structure. It was created by the subduction of different tectonic plates at convergent boundaries around the Pacific Ocean. These include: the Antarctic, Nazca and Cocos plates subducting beneath the South American plate; the Pacific and Juan de Fuca plates beneath the North American plate; the Philippine plate beneath the Eurasian plate; and a complex boundary between the Pacific a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanism
Volcanism, vulcanism, volcanicity, or volcanic activity is the phenomenon where solids, liquids, gases, and their mixtures erupt to the surface of a solid-surface astronomical body such as a planet or a moon. It is caused by the presence of a heat source, usually internally generated, inside the body; the heat is generated by various processes, such as radioactive decay or tidal heating. This heat partially melts solid material in the body or turns material into gas. The mobilized material rises through the body's interior and may break through the solid surface. Causes For volcanism to occur, the temperature of the mantle must have risen to about half its melting point. At this point, the mantle's viscosity will have dropped to about 1021 Pascal-seconds. When large scale melting occurs, the viscosity rapidly falls to 103 Pascal-seconds or even less, increasing the heat transport rate a million-fold. The occurrence of volcanism is partially due to the fact that melted materi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silicic
Silicic is an adjective to describe magma or igneous rock rich in silica. The amount of silica that constitutes a silicic rock is usually defined as at least 63 percent. Granite and rhyolite are the most common silicic rocks. Silicic is the group of silicate magmas which will eventually crystallise a relatively small proportion of ferromagnesian silicates, such as amphibole, pyroxene, and biotite. The main constituents of a silicic rock will be minerals rich in silica-minerals, like silicic feldspar or even free silica as quartz. These are just part of all the other silicate minerals that make up 90% of the earth's crust. This broad classification is refined in practice based on more detained compositional studies where ever possible in the science of mineralology. Example The " Shammar group" is a silicic and volcaniclastic sequence in northwestern Saudi Arabia. See also *Felsic *Mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mount Tongariro
Mount Tongariro (; ) is a compound volcano in the Taupō Volcanic Zone of the North Island of New Zealand. It is located to the southwest of Lake Taupō, and is the northernmost of the three active volcanoes that dominate the landscape of the central North Island. Geology Mount Tongariro is part of the Tongariro volcanic centre, which consists of four massifs made of andesite: Tongariro, Kakaramea-Tihia Massif, Pihanga, and Ruapehu at the southern end of the North Island Volcanic Plateau. The andesitic eruptions formed Tongariro, a steep stratovolcano, reaching a height of . Tongariro is composed of layers of both lava and tephra and the eruptions that built the current stratovolcano commenced about 275,000 years ago. Tongariro consists of at least 12 cones. Ngauruhoe, while often regarded as a separate mountain, is geologically a cone of Tongariro. It is also the most active vent, having erupted more than 70 times since 1839, the last episode in 1973 to 1975. Activ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ōkataina Caldera
Ōkataina Caldera (Ōkataina Volcanic Centre, also spelled Okataina) is a volcano, volcanic caldera and its associated volcanoes located in Taupō Volcanic Zone of New Zealand's North Island. It has several actual or postulated sub calderas. The Ōkataina Caldera is just east of the smaller separate Rotorua Caldera and southwest of the much smaller Rotomā Caldera, Rotomā Embayment which is usually regarded as an associated volcano. It shows high rates of explosive rhyolite, rhyolitic volcanism although its last eruption was basaltic. The postulated Haroharo Caldera contained within it has sometimes been described in almost interchangeable terms with the Ōkataina Caldera or volcanic complex or centre and by other authors as a separate complex defined by gravitational and magnetic features..Possibly started from with the author presuming that certain ignimbrites came from this source. The term Haroharo Caldera was increasingly used in academic papers in the 1970's and 1980's but ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
