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Alexandra Volcanic Group
The Alexandra Volcanic Group (also known as Alexandra volcanic lineament or Alexandra Volcanics) is a chain of extinct calc-alkalic basaltic stratovolcanoes that were most active between 2.74 to 1.60 million years ago but is now known to have had more recent activity between 1.6 to 0.9 million years ago. They extend inland from Mount Karioi near Raglan with Mount Pirongia being the largest, with Pukehoua on the eastern slopes of Pirongia, Kakepuku, Te Kawa, and Tokanui completing the definitive lineament. The associated, but usually separated geologically basaltic monogenetic Okete volcanic field (also known as the Okete Volcanic Formation or Okete Volcanics), lies mainly between Karioi and Pirongia but extends to the east and is quite scattered. Geology The chain extends in the Alexandra volcanic lineament, an alignment striking north-west to south-east over in length and is an example of backarc, intraplate basaltic volcanism that is very rare on land. This is because the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Miocene
The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent" because it has 18% fewer modern marine invertebrates than the Pliocene has. The Miocene is preceded by the Oligocene and is followed by the Pliocene. As Earth went from the Oligocene through the Miocene and into the Pliocene, the climate slowly cooled towards a series of ice ages. The Miocene boundaries are not marked by a single distinct global event but consist rather of regionally defined boundaries between the warmer Oligocene and the cooler Pliocene Epoch. During the Early Miocene, the Arabian Peninsula collided with Eurasia, severing the connection between the Mediterranean and Indian Ocean, and allowing a faunal interchange to occur between Eurasia and Africa, including the dispersal of proboscideans into Eurasia. During the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanic Belt
A volcanic belt is a large volcanically active region. Other terms are used for smaller areas of activity, such as volcanic fields. Volcanic belts are found above zones of unusually high temperature () where magma is created by partial melting of solid material in the Earth's crust and upper mantle. These areas usually form along tectonic plate boundaries at depths of . For example, volcanoes in Mexico and western North America are mostly in volcanic belts, such as the Trans-Mexican Volcanic Belt that extends from west to east across central-southern Mexico and the Northern Cordilleran Volcanic Province in western Canada. The deeply deformed and eroded remnants of ancient volcanic belts are found in volcanically inactive regions such as the Canadian Shield. It contains over 150 volcanic belts (now deformed and eroded down to nearly flat plains) that range from 600 to 1,200 million years old. These are zones of variably metamorphosed mafic to ultramafic volcanic sequences wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geographic Coordinates
The geographic coordinate system (GCS) is a spherical or ellipsoidal coordinate system for measuring and communicating positions directly on the Earth as latitude and longitude. It is the simplest, oldest and most widely used of the various spatial reference systems that are in use, and forms the basis for most others. Although latitude and longitude form a coordinate tuple like a cartesian coordinate system, the geographic coordinate system is not cartesian because the measurements are angles and are not on a planar surface. A full GCS specification, such as those listed in the EPSG and ISO 19111 standards, also includes a choice of geodetic datum (including an Earth ellipsoid), as different datums will yield different latitude and longitude values for the same location. History The invention of a geographic coordinate system is generally credited to Eratosthenes of Cyrene, who composed his now-lost ''Geography'' at the Library of Alexandria in the 3rd century ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tauranga Volcanic Centre
The Tauranga Volcanic Centre is a geologic region in New Zealand's Bay of Plenty. It extends from the southern end of Waihi Beach and from the old volcanoes of the Coromandel Peninsula that make up the northern part of the Kaimai Range, towards the Taupō Volcanic Zone. It was the site, about 2.1 million years ago, of the large single eruption event of Waiteariki ignimbrite with DRE of . Geology The Tauranga Volcanic Centre is at the intersection of the Hauraki and Taupō Rifts and was active during a period of tectonic transition from 2.95 to 1.9 million years ago when major volcanism moved south in Zealandia from the Coromandel Volcanic Zone. It thus has importance geologically as a region of transition, previously classified as part of the Central Volcanic Region, which appears to have commenced as early as 4.5 million years ago from compositional analysis of sea floor eruptives. Part of it to the north west is sometimes defined separately in the literature as the Kaimai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zealandia
Zealandia (pronounced ), also known as (Māori) or Tasmantis, is an almost entirely submerged mass of continental crust that subsided after breaking away from Gondwanaland 83–79 million years ago.Gurnis, M., Hall, C.E., and Lavier, L.L., 2004, Evolving force balance during incipient subduction: Geochemistry, Geophysics, Geosystems, v. 5, Q07001, https://doi.org/10.01029/02003GC000681 It has been described variously as a submerged continent, a continental fragment (or microcontinent), and a continent. The name and concept for Zealandia was proposed by Bruce Luyendyk in 1995, and satellite imagery shows it to be almost the size of Australia. A 2021 study suggests Zealandia is 1 billion years old, about twice as old as geologists previously thought. By approximately 23 million years ago the landmass may have been completely submerged. Today, most of the landmass (94%) remains submerged beneath the Pacific Ocean. New Zealand is the largest part of Zealandia that is above sea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hauraki Rift
The Hauraki Rift is an active NeS-to NWeSE-striking rift valley system in the North Island of New Zealand that has produced the Firth of Thames and the Hauraki Plains. It is approximately wide and long. Geology The rift valley in the north appears to be delimited in the west by the line of the Firth of Thames Fault and to the east by the Hauraki Fault. The mountains of the Coromandel (which include andesitic and basaltic back arc volcanoes) and Kaimai Range to the east and the Hunua Range to the west give it the appearance of a full graben although it has also been described as a simple structure of 2 to 3 half-grabens so the term Hauraki Graben for the low lying portions would be incorrect. However the apparent line in the south of the Firth of Thames Fault no longer follows the apparent horst structure to the west and some believe the line of the Waikato River after it leaves the old Taupō Rift gives a better guide to the western line of the rift as structures have been ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Auckland Volcanic Field
The Auckland volcanic field is an area of monogenetic volcanoes covered by much of the metropolitan area of Auckland, New Zealand's largest city, located in the North Island. The approximately 53 volcanoes in the field have produced a diverse array of maars (explosion craters), tuff rings, scoria cones, and lava flows. With the exception of Rangitoto, no volcano has erupted more than once, but the other eruptions lasted for various periods ranging from a few weeks to several years. Rangitoto erupted several times and recently twice; in an eruption that occurred about 600 years ago, followed by a second eruption approximately 50 years later. The field is fuelled entirely by basaltic magma, unlike the explosive subduction-driven volcanism in the central North Island, such as at Mount Ruapehu and Lake Taupō.Ian E.M. Smith and Sharon R. Allen. Auckland volcanic field geology'. Volcanic Hazards Working Group, Civil Defence Scientific Advisory Committee. Retrieved 30 March 2013. Also ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ngatutura Volcanic Field
The extinct Ngatutura volcanic field that was active between 1.54 and 1.83 million years ago is one of four volcanic fields in an intraplate back arc relationship with the still active Hauraki Rift and the presently dormant Auckland volcanic field. The other volcanic fields, which are part of the Auckland Volcanic Province, are the oldest, Okete to the south near Raglan in late Pliocene times (2.7-1.8 Ma). and to the north the younger South Auckland volcanic field. Geology This field is smaller than the other three and has far fewer basaltic volcanic centres. However at least 16 volcanic centres, mostly scoria cones associated with lava flows of limited hawaiite to nepheline hawaiite composition are known. Some of the basalt deposits in this region of the coast are now known to be related to the West Ngatutura volcanic field with a stratigraphic age of c. 3.5 Ma around 60 km offshore. The earlier work on the field had suggested fewer centres being: #Initial vent #*This w ... [...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] |
Intraplate Volcanism
Intraplate volcanism is volcanism that takes place away from the margins of tectonic plates. Most volcanic activity takes place on plate margins, and there is broad consensus among geologists that this activity is explained well by the theory of plate tectonics. However, the origins of volcanic activity within plates remains controversial. Mechanisms Mechanisms that have been proposed to explain intraplate volcanism include mantle plumes; non-rigid motion within tectonic plates (the plate model); and impact events. It is likely that different mechanisms accounts for different cases of interplate volcanism. Plume model A mantle plume is a proposed mechanism of convection of abnormally hot rock within the Earth's mantle. Because the plume head partly melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hotspots, such as Hawaii or Iceland, and large igneous provinces such as the Deccan and Siberian traps. Some such volcanic regions lie far from t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geology Of The Waikato-King Country Region
The Waikato and King Country regions of New Zealand are built upon a basement of greywacke rocks, which form many of the hills. Much of the land to the west of the Waikato River and in the King Country to the south has been covered by limestone and sandstone, forming bluffs and a karst landscape. The volcanic cones of Karioi and Pirongia dominate the landscape near Raglan and Kawhia Harbours. To the east, the land has been covered with ignimbrite deposits from the Taupo Volcanic Zone. Large amounts of pumice from the Taupo Volcanic Zone have been deposited in the Waikato Basin and Hauraki Plains. Basement rocks As with most of New Zealand, the basement rocks of the Waikato Region and King Country are composed of greywacke (indurated sandstone, siltstone and mudstone). The Waipa Fault passes north–south through the Waikato-King Country region, from Taupiri, along the Waipā River, and south to near Ohura. It represents a major dividing line between different terranes. Murih ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Waikato Plains
The Waikato Plains form a large area of low-lying land in the northwest of the North Island of New Zealand. They are the alluvial plains of the ancient Waikato River, the country's longest river that over the last 1800 years has changed course many times. In the distant past the river flowed northeast from the current Lake Karapiro, exiting near Thames, but in recent times it has flowed northwest to empty into the Tasman Sea near Port Waikato. The plains can be divided roughly into the Waikato Basin (or Middle Waikato Plain), extending in all directions around the city of Hamilton, and the Lower Waikato Plain, nearer the river's mouth. The two are broken by the rough, low-lying hills of the Hakarimata Range, between Ngāruawāhia and Huntly, and the Taupiri Range. The region is heavily populated by New Zealand standards, with over 250,000 people in approximately 8000 km² area. Just over half of these live in Hamilton. The plains are an area of once swampy land, which was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
