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Ohakune Volcanic Complex
The Ohakune volcanic complex (Ohakune craters, Rochfort Crater) is a small extinct monogenetic volcano south-west of Mount Ruapehu and just north of the town of Ohakune in Manawatū-Whanganui, New Zealand. It is in the area of the southernmost volcanic activity in the Taupō Rift and located adjacent to the potentially active Ohakune Fault. Geography The complex is located at the north-western corner of the town of Ohakune at the Tongariro National Park boundary and bisected by the main trunk railway line as it leaves the town to the north-west. Although the Ohakune volcanic complex is also known as the Rochfort Crater, this is the geographical name for the largest of several craters associated with the complex. South of the main trunk railway line is the main scoria cone that reaches a height of and has been quarried on its south-eastern flank. There are a couple of depressions south of the railway line adjacent to the town. North of the line the volcano is mainly fores ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ohakune Fault
Ohakune is a small town at the southern end of Tongariro National Park, close to the southwestern slopes of the active volcano Mount Ruapehu, in the North Island of New Zealand. A rural service town known as New Zealand's Carrot Capital, Ohakune is a popular base in winter for skiers using the ski fields (particularly Turoa) of Mount Ruapehu and in summer for trampers hiking the Tongariro Alpine Crossing. Toponymy The Ngāti Rangi iwi say the Māori language name ''Ohakune'' comes from the phrase "''he Ohakune ki te ao''", which broadly means "an opening to a new world" and refers to the descent from Mount Ruapehu into the valley and swamps of the area. In 2019 the New Zealand Geographic Board changed the official name to ''Ōhakune'', indicating that the first letter was a long vowel, but swiftly reverted to ''Ohakune'' without a macron when Ngāti Rangi objected. History Pre-European history The lands to the south and west of Mount Ruapehu were historically inhabited by t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parasitic Cone
A parasitic cone (also adventive cone, satellite cone, satellitic cone or lateral cone) is the cone-shaped accumulation of volcanic material not part of the central vent of a volcano. It forms from eruptions from fractures on the flank of the volcano. These fractures occur because the flank of the volcano is unstable. Eventually, the fractures reach the magma chamber and generate eruptions called flank eruptions, which, in turn, produce a parasitic cone. A parasitic cone can also be formed from a dike or sill cutting up to the surface from the central magma chamber in an area different from the central vent. A peculiar example of multiple parasitic cones is Jeju Island in South Korea. Jeju Island features 368 " oreums" (Korean: ; "mount"), which lie in a roughly lateral line on either side of the island's central dormant shield volcano Hallasan. See also * Volcanic crater A volcanic crater is an approximately circular depression in the ground caused by volcanic activ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tongariro Volcanic Centre
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 caldera complex, Ōkataina caldera complex and 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 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 Mount Ruapehu in the south, and extends beyond Rotorua in the n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fissure Vent
A fissure vent, also known as a volcanic fissure, eruption fissure or simply a fissure, is a linear volcanic vent through which lava erupts, usually without any explosive activity. The vent is often a few metres wide and may be many kilometres long. Fissure vents can cause large flood basalts which run first in lava channels and later in lava tubes. After some time, the eruption tends to become focused at one or more spatter cones. Volcanic cones and their craters that are aligned along a fissure form a crater row. 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 and the East African Rift. Fissure vents are often part of the structu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dike (geology)
In geology, a dike or dyke is a sheet of rock that is formed in a fracture of a pre-existing rock body. Dikes can be either magmatic or sedimentary in origin. Magmatic dikes form when magma flows into a crack then solidifies as a sheet intrusion, either cutting across layers of rock or through a contiguous mass of rock. Clastic dikes are formed when sediment fills a pre-existing crack.Essentials of Geology, 3rd Ed, Stephen Marshak Magmatic dikes A magmatic dike is a sheet of igneous rock that cuts across older rock beds. It is formed when magma fills a fracture in the older beds and then cools and solidifies. The dike rock is usually more resistant to weathering than the surrounding rock, so that erosion exposes the dike as a natural wall or ridge. It is from these natural walls that dikes get their name. Dikes preserve a record of the fissures through which most mafic magma (fluid magma low in silica) reaches the surface. They are studied by geologists for the clues they ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Taupō Rift Termination Faults
The seismically active southern end of the Taupō Rift beyond Mount Ruapehu has a number of mainly east to west orientated termination faults where the western wall Raurimu Fault and eastern wall Rangipo Fault (Desert Road Fault) terminate in the Ruapehu Graben, of the central North Island of New Zealand. In a multi-fault rupture event there is the potential for the earthquake being of magnitude. The faults can be classified as belonging to three normal fault sets: # Ruapehu Graben NNE‐trending faults #* Raurimu Fault - see separate article #* Rangipo Fault (Desert Road Fault) - see separate article #* Mostly uncharacterised faults under Mount Ruapehu # Ohakune‐Raetihi fault set that is wide of E‐W to ESE‐WNW‐trending faults #* Ohakune Fault #* Raetihi North and South faults #* Waipuna Fault #* Oruakukuru Fault #* Rangiahu Fault #* Maketu Stream Fault (Maketu Trace) # Karioi fault set that is wide of NE‐trending faults #* Karioi Fault #* Wahianoa Fault #* Snowg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wadati–Benioff Zone
A Wadati–Benioff zone (also Benioff–Wadati zone or Benioff zone or Benioff seismic zone) is a planar zone of seismicity corresponding with the down-going slab in a subduction zone. Differential motion along the zone produces numerous earthquakes, the foci of which may be as deep as about . The term was named for the two seismologists, Hugo Benioff of the California Institute of Technology and Kiyoo Wadati of the Japan Meteorological Agency, who independently discovered the zones. Wadati–Benioff zone earthquakes develop beneath volcanic island arcs and continental margins above active subduction zones. They can be produced by slip along the subduction thrust fault or slip on faults within the downgoing plate, as a result of bending and extension as the plate is pulled into the mantle. The deep-focus earthquakes along the zone allow seismologists to map the three-dimensional surface of a subducting slab of oceanic crust and mantle. Discovery In 1949, Hugo Benioff ... [...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 Geology of Mars, 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) to porphyritic (coarse-grained) igneous rock that is intermediate in its content of silica and low in alkali metals. It has less than 20% quartz and 10% feldspa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tonga
Tonga, officially the Kingdom of Tonga, is an island country in Polynesia, part of Oceania. The country has 171 islands, of which 45 are inhabited. Its total surface area is about , scattered over in the southern Pacific Ocean. according to Johnson's Tribune, Tonga has a population of 104,494, 70% of whom reside on the main island, Tongatapu. The country stretches approximately north-south. It is surrounded by Fiji and Wallis and Futuna (France) to the northwest, Samoa to the northeast, New Caledonia (France) and Vanuatu to the west, Niue (the nearest foreign territory) to the east and Kermadec (New Zealand) to the southwest. Tonga is about from New Zealand's North Island. Tonga was first inhabited roughly 2,500 years ago by the Lapita civilization, Polynesian settlers who gradually evolved a distinct and strong ethnic identity, language, and culture as the Tongan people. They quickly established a powerful footing across the South Pacific, and this period of Tong ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kermadec Islands
The Kermadec Islands ( ; ) are a subtropical island arc in the South Pacific Ocean northeast of New Zealand's North Island, and a similar distance southwest of Tonga. The islands are part of New Zealand. They are in total area and uninhabited, except for the permanently staffed Raoul Island Station, the northernmost outpost of New Zealand. The islands are listed with the New Zealand outlying islands. The islands are an immediate part of New Zealand, but not part of any region or district, but instead an ''Area Outside Territorial Authority''. Toponymy The islands were named after the Breton captain Jean-Michel Huon de Kermadec, who visited the islands as part of the d'Entrecasteaux expedition in the 1790s. The topographic particle "Kermadec" is of Breton origin and is a lieu-dit in Pencran in Finistère where '' ker'' means village, residence and ''madec'' a proper name derived from '' mad'' (which means 'good') with the suffix '' -ec'', used to form adjectives indicati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
South Kermadec Ridge Seamounts
The South Kermadec Ridge Seamounts are a continuation of the volcanic island arc, formed at the convergent boundary where the Pacific Plate subducts under the Indo-Australian Plate. The subducting Pacific Plate created the Kermadec Trench, the second deepest submarine trench, to the east of the islands. The seamounts lie along the western aspect of the undersea Kermadec Ridge, which runs southwest from the Kermadec Islands towards the North Island of New Zealand and northeast towards Tonga ( Kermadec-Tonga Arc). This area of the Kermadec Arc - Havre Trough is a relatively young oceanic arc-back-arc system as it became active in the Quaternary. The seamounts include: * Speight Knoll * Oliver Knoll * Haungaroa Seamount * Kuiwai Seamount * Cole Seamount * Ngātoroirangi Seamount * Sonne Seamount * Kibblewhite Seamount * Gill Seamount **Situated in the middle of a deep basin (3000m deep) in the Havre Trough, to the west of Kibblewhite and actually closer to the Lau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rangatauanui
Rangatauanui is a maar lake south of Ohakune in the North Island of New Zealand. It is in the area of the southernmost volcanic activity in the Taupō Rift. Its undisturbed lake sediments have proved useful in reconstructing recent climate proxy records for New Zealand. Geography It is south of Ohakune in the Ngā Roto-o-Rangataua Scenic Reserve, which before 2019 was known as the Ohakune Lakes Scenic Reserve. This has an area of about the about . Historically it has been called Rangataua Crater Lake. Adjacent is another smaller maar lake, Rangatauaiti, in the area that has been called the Rangataua craters in the geological literature. Geology Along with Rangatauaiti it is a maar lake, believed to have been formed about 30,000 years ago. The nearest other volcanoes are to the north, being the Ohakune volcanic complex and it is unclear if the maar lakes are similar potential Ruapehu parasites, representing the southernmost vents of the Taupō Volcanic Zone which is defined ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
