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Mid-Tertiary Ignimbrite Flare-up
The Mid-Tertiary ignimbrite flare-up, was a dramatic period of volcanic eruptions in mid-Cenozoic time, approximately 25–40 million years ago, centered in the western United States. These eruptions are seen today as deposits of ignimbrite, the pyroclastic material that was laid down from these eruptions. Overview There were numerous eruptions within the flare-up. The total volume includes 5x105 km3 of ash flow tuff and 5x106 km3 of intermediate and silicic lava. This amount is on par for some of the largest non-explosive volcanic provinces (see World's largest eruptions). For reference, the 1980 eruption of Mt. St. Helens was about 1 km3. The largest eruption on the flare-up, and also the largest explosive eruption ever known, was the Fish Canyon tuff in southwest Colorado. Its volume alone is 5,000 km3. The three primary volcanic centers of the flare-up are the Central Nevada volcanic field of central Nevada, Indian Peak volcanic field of eastern Nevada/wes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fish Canyon Tuff
The Fish Canyon Tuff is the large volcanic ash flow or ignimbrite deposit resulting from one of the largest known Explosive eruption, explosive eruptions on Earth, estimated at . (see List of largest volcanic eruptions). The Fish Canyon Tuff eruption was centred at the La Garita Caldera in southwest Colorado; the caldera itself would have formed by collapse, as a result of the eruption. Studies of the tuff show that it all belongs to one eruption due to its uniform bulk-chemical composition (SiO2=bulk 67.5–68.5% (dacite), matrix 75–76% (rhyolite) and consistent phenocryst content (35–50%) and mineralogical composition (plagioclase, sanidine, quartz, biotite, hornblende, sphene, apatite, zircon, Fe-Ti oxides are the primary phenocrysts). This tuff and eruption is part of the larger San Juan volcanic field and the Mid-Tertiary_ignimbrite_flare-up, Oligocene Southern Rocky Mountain ignimbrite flare-up. The Fish Canyon Tuff eruption occurred around 28 Million years ago. Sanidine c ... [...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] |
Utah
Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to its west by Nevada. Utah also touches a corner of New Mexico in the southeast. Of the fifty U.S. states, Utah is the 13th-largest by area; with a population over three million, it is the 30th-most-populous and 11th-least-densely populated. Urban development is mostly concentrated in two areas: the Wasatch Front in the north-central part of the state, which is home to roughly two-thirds of the population and includes the capital city, Salt Lake City; and Washington County in the southwest, with more than 180,000 residents. Most of the western half of Utah lies in the Great Basin. Utah has been inhabited for thousands of years by various indigenous groups such as the ancient Puebloans, Navajo and Ute. The Spanish were the first Europe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Slab Gap Hypothesis
In geology, the slab gap hypothesis is one of the explanations put forward to explain several instances of crustal extension that occur inland near former subduction zones. Standard plate tectonic theory holds that once a trench is closed by an overriding plate reaching a rift/spreading center, the plate that has just been fully consumed continues to descend beneath the overriding plate for some time, transmitting compressive pressures to the overriding plate above as well as occasional volcanism. Meanwhile, the descending plate leaves behind it a "window" of inactivity. In this view, there is no mantle upwelling, so once the crustal rift is overridden, the only residual effects are from the remnant descending plate slab. However, actual observations of the crust in western North America where the Farallon Plate's trench and rift was snuffed out millions of years ago by the westward movement of the North American Plate, and replaced by the San Andreas Fault, show not compressi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Large Volume Volcanic Eruptions In The Basin And Range Province
Large volume volcanic eruptions in the Basin and Range Province include Basin and Range eruptions in California, Idaho, Colorado, New Mexico, Texas, Arizona, Nevada, Wyoming and Oregon, as well as those of the Long Valley Caldera geological province and the Yellowstone hotspot. Volcanic fields Some of the volcanic fields within the Basin and Range Province: Northwestern Nevada, the Modoc Plateau, Central Nevada, the Great Basin, Southwestern Nevada, the Mojave Desert, and the Long Valley Caldera region. Named ones include: Coso Volcanic Field, Mono Lake Volcanic Field, Marysvale Volcanic Field, San Juan volcanic field, Indian Peak, Central Colorado volcanic field, Jemez volcanic lineament, Mogollon-Datil volcanic field, Santa Rosa-Calico, and Boot Heel volcanic field. Geological features Many geological features in Western United States have a Northeastern orientation, the North American craton motion has the same orientation as well. For example: the Trans-Challis fault zone, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Slab Window
In geology, a slab window is a gap that forms in a subducted oceanic plate when a mid-ocean ridge meets with a subduction zone and plate divergence at the ridge and convergence at the subduction zone continue, causing the ridge to be subducted.Thorkelson, Derek J., 1996, Subduction of diverging plates and the principles of slab window formation, '' Tectonophysics'', v. 255, p. 47-63 Formation of a slab window produces an area where the crust of the over-riding plate is lacking a rigid lithospheric mantle component and thus is exposed to hot asthenospheric mantle (for a diagram of this, see the link below). This produces anomalous thermal, chemical and physical effects in the mantle that can dramatically change the over-riding plate by interrupting the established tectonic and magmatic regimes. In general, the data used to identify possible slab windows comes from seismic tomography and heat flow studies.van Wijk, J.W., Govers, R., Furlong, K.P., 2001, Three-dimensional thermal m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mantle Wedge
A mantle wedge is a triangular shaped piece of mantle that lies above a subducting tectonic plate and below the overriding plate. This piece of mantle can be identified using seismic velocity imaging as well as earthquake maps. Subducting oceanic slabs carry large amounts of water; this water lowers the melting temperature of the above mantle wedge. Melting of the mantle wedge can also be contributed to depressurization due to the flow in the wedge. This melt gives rise to associated volcanism on the earth's surface. This volcanism can be seen around the world in places such as Japan and Indonesia. Water in mantle wedge Magmas produced in subduction zone regions have high volatile contents. This water is derived from the breakdown of hydrous minerals in the subducting slab, as well as water in the oceanic plate from percolation of seawater. This water rises from the subducting slab to the overriding mantle wedge. The water lowers the melting temperature of the wedge and leave ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flat Slab Subduction
Flat slab subduction is characterized by a low subduction angle (<30 degrees to horizontal) beyond the and a resumption of normal subduction far from the . A slab refers to the subducting lower . Although, some would characterize flat slab as any shallowly dipping lower plate as in western ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Farallon Plate
The Farallon Plate was an ancient oceanic plate. It formed one of the three main plates of Panthalassa, alongside the Phoenix Plate and Izanagi Plate, which were connected by a triple junction. The Farallon Plate began subducting under the west coast of the North American Plate—then located in modern Utah—as Pangaea broke apart and after the formation of the Pacific Plate at the centre of the triple junction during the Early Jurassic. It is named for the Farallon Islands, which are located just west of San Francisco, California. Over time, the central part of the Farallon Plate was completely subducted under the southwestern part of the North American Plate. The remains of the Farallon Plate are the Juan de Fuca, Explorer and Gorda Plates, subducting under the northern part of the North American Plate; the Cocos Plate subducting under Central America; and the Nazca Plate subducting under the South American Plate. The Farallon Plate is also responsible for transporting old i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laramide Orogeny
The Laramide orogeny was a time period of mountain building in western North America, which started in the Late Cretaceous, 70 to 80 million years ago, and ended 35 to 55 million years ago. The exact duration and ages of beginning and end of the orogeny are in dispute. The Laramide orogeny occurred in a series of pulses, with quiescent phases intervening. The major feature that was created by this orogeny was deep-seated, thick-skinned deformation, with evidence of this orogeny found from Canada to northern Mexico, with the easternmost extent of the mountain-building represented by the Black Hills of South Dakota. The phenomenon is named for the Laramie Mountains of eastern Wyoming. The Laramide orogeny is sometimes confused with the Sevier orogeny, which partially overlapped in time and space. The orogeny is commonly attributed to events off the west coast of North America, where the Kula Plate, Kula and Farallon Plates were sliding under the North American plate. Most hypothes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Slab Rollback
Oceanic trenches are prominent long, narrow topographic depressions of the ocean floor. They are typically wide and below the level of the surrounding oceanic floor, but can be thousands of kilometers in length. There are about of oceanic trenches worldwide, mostly around the Pacific Ocean, but also in the eastern Indian Ocean and a few other locations. The greatest ocean depth measured is in the Challenger Deep of the Mariana Trench, at a depth of below sea level. Oceanic trenches are a feature of the Earth's distinctive plate tectonics. They mark the locations of Convergent boundary, convergent plate boundaries, along which Lithosphere, lithospheric Plate tectonics, plates move towards each other at rates that vary from a few millimeters to over ten centimeters per year. Oceanic lithosphere moves into trenches at a global rate of about 3 km2/yr. A trench marks the position at which the flexed, subduction, subducting Slab (geology), slab begins to descend beneath anothe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tectonic
Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents known as cratons, and the ways in which the relatively rigid plates that constitute the Earth's outer shell interact with each other. Tectonics also provide a framework for understanding the earthquake and volcanic belts that directly affect much of the global population. Tectonic studies are important as guides for economic geologists searching for fossil fuels and ore deposits of metallic and nonmetallic resources. An understanding of tectonic principles is essential to geomorphologists to explain erosion patterns and other Earth surface features. Main types of tectonic regime Extensional tectonics Extensional tectonics is associated with the stretching and thinning of the crust or the lithosphere. This type of tectonics is found ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
