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Tarahi (volcano)
Tarahi is a high andesite volcano, in the Kaikohe-Bay of Islands volcanic field in New Zealand. Northwest of Tarahi is a smaller, basaltic scoria cone, Haruru pā, before the higher cone of Te Ahuahu. To its immediate east is Putahi and the location of a famous battle of the Flagstaff War adjacent to Lake Ōmāpere Lake Ōmāpere is the largest lake in the Northland Region of New Zealand. It is located to the North of Kaikohe. The lake sits within the Kaikohe-Bay of Islands volcanic field. The lake was formed when an ancient lava flow blocked a valley, form .... References Geological Society of New Zealand Volcanoes of the Northland Region Far North District {{Northland-geo-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kaikohe-Bay Of Islands Volcanic Field
The recently active basaltic Kaikohe-Bay of Islands volcanic field in the Northland Region of New Zealand is associated geographically with an older region of extinct volcanism to its north the Wairakau Volcanic Centre, meaning eruptions in this region have occurred over the last 20 million years. All the cones older than 2 million years have eroded away, leaving plateaus from Ōkaihau to Kerikeri and north to Whangaroa from the old andesite/dacite stratovolcanoes of the Wairakau Volcanic Centre and the ten million year old or more recent volcanoes in field towards the south. In the southern part of the field, around 12 small basaltic scoria cones, and a rhyolite dome erupted in the last 500,000 years around Kaikohe. The field is considered dormant, rather than extinct. Tectonics The field is part of the eastern Northland volcanic belt which extends south to the Whangārei volcanic field near Whangarei and the south east volcanics of the Taurikura volcanic complex as found i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Putahi
Putahi is a 381 m high rhyolite dome, in the Kaikohe-Bay of Islands volcanic field in New Zealand. To the north of Putahi is Lake Ōmāpere. To its north east are the volcanoes of Tarahi and Te Ahuahu. It was the site of the first, successful for the British, battle of the Flagstaff War of 1845–46 against Hone Heke's Ngāpuhi tribe fraction. Lieutenant-Colonel William Hulme and his force of about 200 soldiers, marines and volunteers having destroyed a coastal pā at Ōtuihu moved on Hone Heke at his new pā (Te Mawhe Pā) on the Lake Ōmāpere side of Puketutu which they arrived at on 7th May 1845 before its fortifications were fully complete. However the next day, they were attacked on the flank by a force of 140 fighters led by Te Ruki Kawiti and as the British dealt with this, Hone Heke attacked from the pā defences. In the fierce running battle that ensured the Ngāpuhi Ngāpuhi (or Ngā Puhi) is a Māori iwi associated with the Northland region of New Zealand ... [...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] |
Te Ahuahu
Te Ahuahu is a 373 m high basaltic scoria cone, in the Kaikohe-Bay of Islands volcanic field in New Zealand. It was the site of Hone Heke's pā that was the scene of the Battle of Te Ahuahu during the Flagstaff War The Flagstaff War, also known as Heke's War, Hōne Heke's Rebellion and the Northern War, was fought between 11 March 1845 and 11 January 1846 in and around the Bay of Islands, New Zealand. The conflict is best remembered for the actions of Hō ... of 1845–46. References Geological Society of New Zealand Forts in New Zealand Far North District Volcanoes of the Northland Region Volcanic cones Flagstaff War {{Northland-geo-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pa (Māori)
Pa, pa, PA, P.A. or pA may refer to: Businesses and organisations Government and military * Palestinian National Authority, also called Palestinian Authority, interim governing body of the Gaza Strip and part of the West Bank * Pakistan Army * People's Association (Singapore), a Singaporean grassroots statutory board * Philippine Army * Patrulla Águila * Planning Authority, a government agency of Malta Airlines * Pan American World Airways, IATA airline designator PA (to 1991) * Florida Coastal Airlines, IATA airline designator PA (1995–2010) * Airblue, IATA airline designator PA (from 2003) Other * Progressive Alliance, a political international of social-democratic, socialist and progressive political parties and organisations * Professional association, a type of business organization * PA Consulting Group * PA Media, a news agency in the UK and Ireland, formerly the Press Association * Produttori Associati, an Italian record label Linguistics * Pa (cuneiform), a cun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basalt
Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of all volcanic rock on Earth is basalt. Rapid-cooling, fine-grained basalt is chemically equivalent to slow-cooling, coarse-grained gabbro. The eruption of basalt lava is observed by geologists at about 20 volcanoes per year. Basalt is also an important rock type on other planetary bodies in the Solar System. For example, the bulk of the plains of Venus, which cover ~80% of the surface, are basaltic; the lunar maria are plains of flood-basaltic lava flows; and basalt is a common rock on the surface of Mars. Molten basalt lava has a low viscosity due to its relatively low silica content (between 45% and 52%), resulting in rapidly moving lava flows that can spread over great areas before cooling and solidifying. Flood basalts are t ... [...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 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 transitions to the rhyolites. The relative proportions of feldspars and quartz ... [...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 ... [...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-'' ireand ''imbri-'' ain Ignimbrites are made of a very poorly sorted mixture of volcanic ash (or tuff when 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 density. Many pale i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intrusive Rock
Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form '' intrusions'', such as batholiths, dikes, sills, laccoliths, and volcanic necks.Intrusive RocksIntrusive rocks accessdate: March 27, 2017.Igneous intrusive rocks, accessdate: March 27, 2017.Britannica.comintrusive rock , geology , Britannica.com accessdate: March 27, 2017. Intrusion is one of the two ways igneous rock can form. The other is extrusion, such as a volcanic eruption or similar event. An intrusion is any body of intrusive igneous rock, formed from magma that cools and solidifies within the crust of the planet. In contrast, an ''extrusion'' consists of extrusive rock, formed above the surface of the crust. Some geologists use the term plutonic rock synonymously with intrusive rock, but other geologists subdivide intrusive rock, by crystal size, into coarse-grained plutonic rock (typically formed deeper in the Earth's crust in batholiths or stocks) an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pleistocene
The Pleistocene ( , often referred to as the ''Ice age'') is the geological 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 a faunal interchange between the two reg ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
