1.
Supervolcano (film)
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Supervolcano is a disaster television film that originally aired on 13 March 2005 on BBC One, and released by the BBC on 10 April 2005 on the Discovery Channel. It is centered on the speculated and potential eruption of the caldera of Yellowstone National Park. Its tagline is Scientists know it as the deadliest volcano on Earth, the film begins with a group of hooded people in caribou parkas riding through snow on snowmobiles. Arriving at a nearly buried building, inside they find a video recorded journal of a man who appears to be dying and he tells he is Richard Lieberman, the scientist who was in charge of Yellowstone Volcano Observatory. A woman named Maggie Chin asks about the possibility of a super eruption, the next day, the USGS observes a 6.9 earthquake which causes a tsunami wave to slam into the Fishing Bridge area of the park. This prompts Maggie to press again, asking Rick if a supereruption is still possible, however, this does not stop her from appearing with Kenneth Weilly on KTCU news to discuss Kens new book on volcanoes. He tells the difference between a volcanic eruption and a super volcanic eruption. He then goes on to say that the Yellowstone volcano has shown a pattern of erupting every 600,000 years, Rick, who is observing the interview, is angered at Kens words and it is revealed the two are brothers-in-law. The USGS are swarmed with calls, to which all say that the eruption is not imminent and their argument is interrupted by Fiona Lieberman, Ricks wife and Kens sister. She reflects that Rick is cautious of what he says in public due to the press convincing people Yellowstone was going to erupt due to the discovery of a bulge in Yellowstone Lake some years before. Wendy Reiss, the undersecretary of FEMA, visits and asks Rick about the worst case scenario if Yellowstone does release a super eruption and he shows her a model, revealing devastating results of the ash fall over the US. She asks him if the eruption will happen, to which he says Is it going to happen, now, is it going to happen in our lifetime. And that is the most honest answer anyone can give you, a hydrothermal event at the Norris Geyser Basin draws yet another calamity with the press. Specifically Maggie once again as she tries to press Rick into saying the event is an indicator of volcanic activity, Rick once again tells her that it was not a volcanic event, and he leave the conference. The team decides they need better images of the chamber and to see what was happening at ground level, the team begins to get on edge due to earthquake swarms, rising levels of carbon dioxide killing trees, as well as events before the hydrothermal event. These all could be indicators of activity, but they know that they are not sure fire signs either. They close the park, but to their horror, they find harmonic tremor near Norris and this is indicating an eruption is imminent because magma is now on the move. Not only that, but shortly after the harmonic is detected, animals begin to flee the park in droves, Rick, worried about what is happening, sends his family to London to visit Fionas mother
2.
Volcanic explosivity index
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The Volcanic Explosivity Index is a relative measure of the explosiveness of volcanic eruptions. It was devised by Chris Newhall of the United States Geological Survey, volume of products, eruption cloud height, and qualitative observations are used to determine the explosivity value. The scale is open-ended with the largest volcanoes in history given magnitude 8, the scale is logarithmic, with each interval on the scale representing a tenfold increase in observed ejecta criteria, with the exception of between VEI0, VEI1 and VEI2. With indices running from 0 to 8, the VEI associated with an eruption is dependent on how much material is thrown out, to what height. The scale is logarithmic from VEI2 and up, an increase of 1 index indicates an eruption that is 10 times as powerful, as such there is a discontinuity in the definition of the VEI between indices 1 and 2. The lower border of the volume of ejecta jumps by a factor of 100 from 10,000 to 1,000,000 m3 while the factor is 10 between all higher indices. In the following table, the frequency of each VEI indicates the frequency of new eruptions of that VEI or higher. A total of 47 eruptions of VEI8 magnitude or above, ranging in age from Ordovician to Pleistocene, have been identified, of which 42 occurred in the past 36 million years. The most recent is Lake Taupos Oruanui eruption,25,360 years ago, there have been at least five identified Holocene eruptions with a VEI of 7. There are also 58 plinian eruptions, and 13 caldera-forming eruptions, of large, there are likely many other eruptions that are not identified. About 90% of these 7,742 eruptions have a VEI of 3 or less, about 49% of these 7,742 eruptions have a VEI of 2. Under the VEI, ash, lava, lava bombs and ignimbrite are all treated alike, density and vesicularity of the volcanic products in question is not taken into account. In contrast, the DRE is sometimes calculated to give the amount of magma erupted. Another weakness of the VEI is that it does not take account the power output of an eruption. Tephra, or fallout sediment analysis, can provide an estimate of the explosiveness of a known eruption event and it is, however, not obviously related to the amount of SO2 emitted by the eruption. The VEI itself is inadequate for describing the effects of volcanic eruptions. This is clearly demonstrated by two eruptions, Agung and El Chichón
3.
United States Geological Survey
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The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its resources. The organization has four science disciplines, concerning biology, geography, geology. The USGS is a research organization with no regulatory responsibility. The USGS is a bureau of the United States Department of the Interior, the USGS employs approximately 8,670 people and is headquartered in Reston, Virginia. The USGS also has major offices near Lakewood, Colorado, at the Denver Federal Center, the current motto of the USGS, in use since August 1997, is science for a changing world. The agencys previous slogan, adopted on the occasion of its anniversary, was Earth Science in the Public Service. Prompted by a report from the National Academy of Sciences, the USGS was created, by a last-minute amendment and it was charged with the classification of the public lands, and examination of the geological structure, mineral resources, and products of the national domain. This task was driven by the need to inventory the vast lands added to the United States by the Louisiana Purchase in 1803, the legislation also provided that the Hayden, Powell, and Wheeler surveys be discontinued as of June 30,1879. Clarence King, the first director of USGS, assembled the new organization from disparate regional survey agencies, after a short tenure, King was succeeded in the directors chair by John Wesley Powell. Administratively, it is divided into a Headquarters unit and six Regional Units, Other specific programs include, Earthquake Hazards Program monitors earthquake activity worldwide. The National Earthquake Information Center in Golden, Colorado on the campus of the Colorado School of Mines detects the location, the USGS also runs or supports several regional monitoring networks in the United States under the umbrella of the Advanced National Seismic System. The USGS informs authorities, emergency responders, the media, and it also maintains long-term archives of earthquake data for scientific and engineering research. It also conducts and supports research on long-term seismic hazards, USGS has released the UCERF California earthquake forecast. The USGS National Geomagnetism Program monitors the magnetic field at magnetic observatories and distributes magnetometer data in real time, the USGS operates the streamgaging network for the United States, with over 7400 streamgages. Real-time streamflow data are available online, since 1962, the Astrogeology Research Program has been involved in global, lunar, and planetary exploration and mapping. USGS operates a number of related programs, notably the National Streamflow Information Program. USGS Water data is available from their National Water Information System database
4.
Volcanic eruption
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Several types of volcanic eruptions—during which lava, tephra, and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has been observed, some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types all in one eruptive series. There are three different types of eruptions, the most well-observed are magmatic eruptions, which involve the decompression of gas within magma that propels it forward. Phreatomagmatic eruptions are another type of eruption, driven by the compression of gas within magma. Within these wide-defining eruptive types are several subtypes, the weakest are Hawaiian and submarine, then Strombolian, followed by Vulcanian and Surtseyan. The stronger eruptive types are Pelean eruptions, followed by Plinian eruptions, subglacial and phreatic eruptions are defined by their eruptive mechanism, and vary in strength. An important measure of strength is Volcanic Explosivity Index, an order of magnitude scale ranging from 0 to 8 that often correlates to eruptive types. Explosive eruptions are characterized by gas-driven explosions that propels magma and tephra, effusive eruptions, meanwhile, are characterized by the outpouring of lava without significant explosive eruption. Volcanic eruptions vary widely in strength, on the one extreme there are effusive Hawaiian eruptions, which are characterized by lava fountains and fluid lava flows, which are typically not very dangerous. On the other extreme, Plinian eruptions are large, violent, volcanoes are not bound to one eruptive style, and frequently display many different types, both passive and explosive, even the span of a single eruptive cycle. Volcanoes do not always erupt vertically from a crater near their peak. Some volcanoes exhibit lateral and fissure eruptions, notably, many Hawaiian eruptions start from rift zones, and some of the strongest Surtseyan eruptions develop along fracture zones. Scientists believed that pulses of magma mixed together in the chamber before climbing upward—a process estimated to several thousands of years. But Columbia University volcanologists found that the eruption of Costa Rica’s Irazú Volcano in 1963 was likely triggered by magma that took a route from the mantle over just a few months. The volcanic explosivity index is a scale, from 0 to 8 and it is used by the Smithsonian Institutions Global Volcanism Program in assessing the impact of historic and prehistoric lava flows. It operates in a way similar to the Richter scale for earthquakes, the vast majority of volcanic eruptions are of VEIs between 0 and 2. Volcanic eruptions by VEI index Magmatic eruptions produce juvenile clasts during explosive decompression from gas release, Hawaiian eruptions are a type of volcanic eruption, named after the Hawaiian volcanoes with which this eruptive type is hallmark. Hawaiian eruptions are the calmest types of events, characterized by the effusive eruption of very fluid basalt-type lavas with low gaseous content
5.
Volcanic Explosivity Index
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The Volcanic Explosivity Index is a relative measure of the explosiveness of volcanic eruptions. It was devised by Chris Newhall of the United States Geological Survey, volume of products, eruption cloud height, and qualitative observations are used to determine the explosivity value. The scale is open-ended with the largest volcanoes in history given magnitude 8, the scale is logarithmic, with each interval on the scale representing a tenfold increase in observed ejecta criteria, with the exception of between VEI0, VEI1 and VEI2. With indices running from 0 to 8, the VEI associated with an eruption is dependent on how much material is thrown out, to what height. The scale is logarithmic from VEI2 and up, an increase of 1 index indicates an eruption that is 10 times as powerful, as such there is a discontinuity in the definition of the VEI between indices 1 and 2. The lower border of the volume of ejecta jumps by a factor of 100 from 10,000 to 1,000,000 m3 while the factor is 10 between all higher indices. In the following table, the frequency of each VEI indicates the frequency of new eruptions of that VEI or higher. A total of 47 eruptions of VEI8 magnitude or above, ranging in age from Ordovician to Pleistocene, have been identified, of which 42 occurred in the past 36 million years. The most recent is Lake Taupos Oruanui eruption,25,360 years ago, there have been at least five identified Holocene eruptions with a VEI of 7. There are also 58 plinian eruptions, and 13 caldera-forming eruptions, of large, there are likely many other eruptions that are not identified. About 90% of these 7,742 eruptions have a VEI of 3 or less, about 49% of these 7,742 eruptions have a VEI of 2. Under the VEI, ash, lava, lava bombs and ignimbrite are all treated alike, density and vesicularity of the volcanic products in question is not taken into account. In contrast, the DRE is sometimes calculated to give the amount of magma erupted. Another weakness of the VEI is that it does not take account the power output of an eruption. Tephra, or fallout sediment analysis, can provide an estimate of the explosiveness of a known eruption event and it is, however, not obviously related to the amount of SO2 emitted by the eruption. The VEI itself is inadequate for describing the effects of volcanic eruptions. This is clearly demonstrated by two eruptions, Agung and El Chichón
6.
Lava
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Lava is the molten rock expelled by a volcano during an eruption. The resulting rock after solidification and cooling is called lava. The molten rock is formed in the interior of planets, including Earth. The source of the heat melts the rock within the earth is geothermal energy. When first erupted from a vent, lava is a liquid usually at temperatures from 700 to 1,200 °C. A lava flow is an outpouring of lava, which is created during a non-explosive effusive eruption. When it has stopped moving, lava solidifies to form igneous rock, the term lava flow is commonly shortened to lava. Although lava can be up to 100,000 times more viscous than water, lava can flow great distances before cooling and solidifying because of its thixotropic, explosive eruptions produce a mixture of volcanic ash and other fragments called tephra, rather than lava flows. The word lava comes from Italian, and is derived from the Latin word labes which means a fall or slide. The first use in connection with extruded magma was apparently in an account written by Francesco Serao on the eruption of Vesuvius between May 14 and June 4,1737. Serao described a flow of lava as an analogy to the flow of water. The composition of almost all lava of the Earths crust is dominated by silicate minerals, mostly feldspars, olivine, pyroxenes, amphiboles, micas, igneous rocks, which form lava flows when erupted, can be classified into three chemical types, felsic, intermediate, and mafic. These classes are primarily chemical, however, the chemistry of lava also tends to correlate with the temperature, its viscosity. Felsic or silicic lavas such as rhyolite and dacite typically form lava spines, most silicic lava flows are extremely viscous, and typically fragment as they extrude, producing blocky autobreccias. Felsic magmas can erupt at temperatures as low as 650 to 750 °C, unusually hot rhyolite lavas, however, may flow for distances of many tens of kilometres, such as in the Snake River Plain of the northwestern United States. Intermediate or andesitic lavas are lower in aluminium and silica, and usually somewhat richer in magnesium, intermediate lavas form andesite domes and block lavas, and may occur on steep composite volcanoes, such as in the Andes. Poorer in aluminium and silica than felsic lavas, and also commonly hotter, greater temperatures tend to destroy polymerized bonds within the magma, promoting more fluid behaviour and also a greater tendency to form phenocrysts. Higher iron and magnesium tends to manifest as a darker groundmass, mafic or basaltic lavas are typified by their high ferromagnesian content, and generally erupt at temperatures in excess of 950 °C
7.
Magma
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Besides molten rock, magma may also contain suspended crystals, dissolved gas and sometimes gas bubbles. Magma often collects in magma chambers that may feed a volcano or solidify underground to form an intrusion, magma is capable of intruding into adjacent rocks, extrusion onto the surface as lava, and explosive ejection as tephra to form pyroclastic rock. Magma is a complex high-temperature fluid substance, temperatures of most magmas are in the range 700 °C to 1300 °C, but very rare carbonatite magmas may be as cool as 600 °C, and komatiite magmas may have been as hot as 1600 °C. Environments of magma formation and compositions are commonly correlated, environments include subduction zones, continental rift zones, mid-ocean ridges and hotspots. Despite being found in such locales, the bulk of the Earths crust. Except for the outer core, most of the Earth takes the form of a rheid. Magma, as liquid, preferentially forms in high temperature, low pressure environments within several kilometers of the Earths surface, magma compositions may evolve after formation by fractional crystallization, contamination, and magma mixing. By definition rock formed of solidified magma is called igneous rock, melting of solid rocks to form magma is controlled by three physical parameters, temperature, pressure, and composition. Mechanisms are discussed in the entry for igneous rock, as a rock melts, its volume changes. When enough rock is melted, the small globules of melt link up, under pressure within the earth, as little as a fraction of a percent partial melting may be sufficient to cause melt to be squeezed from its source. The degree of melting is critical for determining what type of magma is produced. The degree of partial melting required to form a melt can be estimated by considering the relative enrichment of incompatible elements versus compatible elements, incompatible elements commonly include potassium, barium, cesium, and rubidium. Rock types produced by small degrees of melting in the Earths mantle are typically alkaline. Typically, primitive melts of this composition form lamprophyre, lamproite, kimberlite and sometimes nepheline-bearing mafic rocks such as alkali basalts, pegmatite may be produced by low degrees of partial melting of the crust. Some granite-composition magmas are eutectic melts, and they may be produced by low to high degrees of melting of the crust. At high degrees of melting of the crust, granitoids such as tonalite, granodiorite and monzonite can be produced. Being only the time in recorded history that magma had been reached, IDDP decided to invest in the hole. A cemented steel case was constructed in the hole with a perforation at the close to the magma
8.
Mantle (geology)
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The mantle is a layer inside a terrestrial planet and some other rocky planetary bodies. For a mantle to form, the body must be large enough to have undergone the process of planetary differentiation by density. The mantle surrounds the planetary core, the mantle is surrounded by the crust. The terrestrial planets, the Moon, two of Jupiters moons and the asteroid Vesta each have a made of silicate rock. Interpretation of spacecraft data suggests that at least two moons of Jupiter, as well as Titan and Triton each have a mantle made of ice or other solid volatile substances. The interior of Earth, similar to the terrestrial planets, is divided into layers of different composition. The mantle is a layer between the crust and the outer core, Earths mantle is a silicate rocky shell with an average thickness of 2,886 kilometres. The mantle makes up about 84% of Earths volume and it is predominantly solid but in geological time it behaves as a very viscous fluid. The mantle encloses the hot core rich in iron and nickel, past episodes of melting and volcanism at the shallower levels of the mantle have produced a thin crust of crystallized melt products near the surface. A thin crust, the part of the lithosphere, surrounds the mantle and is about 5 to 75 km thick. In some places under the ocean the mantle is exposed on the surface of Earth. The mantle is divided into sections which are based upon results from seismology and these layers are the following, the upper mantle, the transition zone, the lower mantle, and anomalous core–mantle boundary with a variable thickness. The uppermost mantle plus overlying crust are relatively rigid and form the lithosphere, below the lithosphere the upper mantle becomes notably more plastic. In some regions below the lithosphere, the shear velocity is reduced. Inge Lehmann discovered a seismic discontinuity at about 220 km depth, although this discontinuity has been found in other studies, the transition zone is an area of great complexity, it physically separates the upper and lower mantle. Very little is known about the lower mantle apart from that it appears to be relatively seismically homogeneous, the D layer at the core–mantle boundary separates the mantle from the core. A principal source of the heat that drives plate tectonics is the decay of uranium, thorium. The mantle differs substantially from the crust in its properties as the direct consequence of the difference in composition
9.
Crust (geology)
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In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle. The crust of the Earth is composed of a variety of igneous, metamorphic. The crust is underlain by the mantle, the upper part of the mantle is composed mostly of peridotite, a rock denser than rocks common in the overlying crust. The boundary between the crust and mantle is conventionally placed at the Mohorovičić discontinuity, a boundary defined by a contrast in seismic velocity, the crust occupies less than 1% of Earths volume. The crust of the Earth is of two types, oceanic and continental. The oceanic crust is 5 km to 10 km thick and is composed primarily of basalt, diabase, the continental crust is typically from 30 km to 50 km thick and is mostly composed of slightly less dense rocks than those of the oceanic crust. Some of these less dense rocks, such as granite, are common in the continental crust, both the continental and oceanic crust float on the mantle. Because the continental crust is thicker, it both to greater elevations and greater depth than the oceanic crust. The slightly lower density of continental rock compared to basaltic oceanic rock contributes to the higher relative elevation of the top of the continental crust. As the top of the continental crust reaches elevations higher than that of the oceanic, the temperature of the crust increases with depth, reaching values typically in the range from about 200 °C to 400 °C at the boundary with the underlying mantle. The crust and underlying relatively rigid uppermost mantle make up the lithosphere, because of convection in the underlying plastic upper mantle and asthenosphere, the lithosphere is broken into tectonic plates that move. The temperature increases by as much as 30 °C for every kilometer locally in the part of the crust. Earth has probably always had some form of basaltic crust, in contrast, the bulk of the continental crust is much older. The oldest continental crustal rocks on Earth have ages in the range from about 3.7 to 4, some zircon with age as great as 4.3 billion years has been found in the Narryer Gneiss Terrane. The average age of the current Earths continental crust has been estimated to be about 2.0 billion years, most crustal rocks formed before 2.5 billion years ago are located in cratons. Such old continental crust and the underlying mantle asthenosphere are less dense than elsewhere in Earth, formation of new continental crust is linked to periods of intense orogeny, these periods coincide with the formation of the supercontinents such as Rodinia, Pangaea and Gondwana. The continental crust has a composition similar to that of andesite. The most abundant minerals in Earths continental crust are feldspars, which make up about 41% of the crust by weight, followed by quartz at 12%, Continental crust is enriched in incompatible elements compared to the basaltic ocean crust and much enriched compared to the underlying mantle
10.
Hotspot (geology)
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In geology, the places known as hotspots or hot spots are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. They may be on, near to, or far from plate boundaries. Currently, there are two hypotheses that attempt to explain their origins, one suggests that hotspots are due to mantle plumes that rise as thermal diapirs from the core–mantle boundary. The other hypothesis is that lithospheric extension permits the passive rising of melt from shallow depths and this hypothesis considers the term hotspot to be a misnomer, asserting that the mantle source beneath them is, in fact, not anomalously hot at all. Well known examples include Hawaii, Iceland and Yellowstone and it was later postulated that hotspots are fed by narrow streams of hot mantle rising from the Earths core–mantle boundary in a structure called a mantle plume. Whether or not such mantle plumes exist is currently the subject of a controversy in Earth science. Estimates for the number of hotspots postulated to be fed by mantle plumes has ranged from about 20 to several thousands, over the years, Hawaii, Réunion, Yellowstone, Galápagos, and Iceland are some of the currently most active volcanic regions to which the hypothesis is applied. As a result, they are less explosive than subduction zone volcanoes, where hotspots occur in continental regions, basaltic magma rises through the continental crust, which melts to form rhyolites. These rhyolites can form violent eruptions, for example, the Yellowstone Caldera was formed by some of the most powerful volcanic explosions in geologic history. However, when the rhyolite is completely erupted, it may be followed by eruptions of basaltic magma rising through the same lithospheric fissures, the hotspot hypothesis is now closely linked to the mantle plume hypothesis. Hotspot volcanoes are considered to have a different origin from island arc volcanoes. The latter form over subduction zones, at converging plate boundaries, when one oceanic plate meets another, the denser plate is forced downward into a deep ocean trench. This plate, as it is subducted, releases water into the base of the plate. It is this that fuels a chain of volcanoes, such as the Aleutian Islands, the joint mantle plume/hotspot hypothesis envisages the feeder structures to be fixed relative to one another, with the continents and seafloor drifting overhead. The hypothesis thus predicts that time-progressive chains of volcanoes are developed on the surface, examples are Yellowstone, which lies at the end of a chain of extinct calderas, which become progressively older to the west. Another example is the Hawaiian archipelago, where islands become progressively older, boschi, L. Becker, T. W. Steinberger, B. Mantle plumes, Dynamic models and seismic images, break-up spots, Could the Pacific open as a consequence of plate kinematics. Towards A Better Understanding Of Hot Spot Volcanism, formation of Hotspots Raising Hot Spots Large Igneous Provinces Maria Antretter, PhD Thesis, Moving hotspots – Evidence from paleomagnetism and modeling Do Plumes Exist
11.
Yellowstone Caldera
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The Yellowstone Caldera is a volcanic caldera and supervolcano located in Yellowstone National Park in the United States, sometimes referred to as the Yellowstone Supervolcano. The caldera and most of the park are located in the northwest corner of Wyoming, the major features of the caldera measure about 34 by 45 miles. The source of the Yellowstone hotspot is controversial, some geoscientists hypothesize that the Yellowstone hotspot is the effect of an interaction between local conditions in the lithosphere and upper mantle convection. Others suggest a deep mantle origin, part of the controversy is the relatively sudden appearance of the hotspot in the geologic record. Additionally, the Columbia Basalt flows appeared at the approximate time. Volcanism at Yellowstone is relatively recent with calderas that were created during large eruptions that took place 2.1 million,1.3 million, the calderas lie over a hotspot where light, hot, molten rock from the mantle rises toward the surface. While the Yellowstone hotspot is now under the Yellowstone Plateau, it helped create the eastern Snake River Plain through a series of huge volcanic eruptions. Over the past 18 million years or so, this hotspot has generated a succession of violent eruptions, together these eruptions have helped create the eastern part of the Snake River Plain from a once-mountainous region. At least a dozen of these eruptions were so massive that they are classified as supereruptions, volcanic eruptions sometimes empty their stores of magma so swiftly that they cause the overlying land to collapse into the emptied magma chamber, forming a geographic depression called a caldera. The loosely defined term supervolcano has been used to describe volcanic fields that produce exceptionally large volcanic eruptions. The three supereruptions occurred 2.1 million,1.3 million, and approximately 630,000 years ago, forming the Island Park Caldera, the Henrys Fork Caldera, and Yellowstone calderas, respectively. The Island Park Caldera supereruption, which produced the Huckleberry Ridge Tuff, was the largest, the next biggest supereruption formed the Yellowstone Caldera and produced the Lava Creek Tuff. The Henrys Fork Caldera produced the smaller Mesa Falls Tuff but is the caldera from the Snake River Plain-Yellowstone hotspot that is plainly visible today. Non-explosive eruptions of lava and less-violent explosive eruptions have occurred in, the most recent lava flow occurred about 70,000 years ago, while a violent eruption excavated the West Thumb of Lake Yellowstone around 150,000 years ago. Smaller steam explosions occur as well, an explosion 13,800 years ago left a 5 km diameter crater at Mary Bay on the edge of Yellowstone Lake. The volcanic eruptions, as well as the geothermal activity, are a result of a great cove of magma located below the calderas surface. The magma in this cove contains gases that are dissolved by the immense pressure that the magma is under. If the pressure is released to a sufficient degree by some geological shift, then some of the bubble out
12.
Subduction
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Subduction is a geological process that takes place at convergent boundaries of tectonic plates where one plate moves under another and is forced or sinks due to gravity into the mantle. Regions where this occurs are known as subduction zones. Rates of subduction are typically in centimeters per year, with the rate of convergence being approximately two to eight centimeters per year along most plate boundaries. Plates include both oceanic crust and continental crust, stable subduction zones involve the oceanic lithosphere of one plate sliding beneath the continental or oceanic lithosphere of another plate due to the higher density of the oceanic lithosphere. That is, the lithosphere is always oceanic while the overriding lithosphere may or may not be oceanic. Subduction zones are sites that have a rate of volcanism, earthquakes. Subduction zones are sites of convective downwelling of Earths lithosphere, subduction zones exist at convergent plate boundaries where one plate of oceanic lithosphere converges with another plate. The descending slab, the plate, is over-ridden by the leading edge of the other plate. The slab sinks at an angle of approximately twenty-five to forty-five degrees to Earths surface and this sinking is driven by the temperature difference between the subducting oceanic lithosphere and the surrounding mantle asthenosphere, as the colder oceanic lithosphere is, on average, denser. At a depth of approximately 80–120 kilometers, the basalt of the oceanic crust is converted to a rock called eclogite. At that point, the density of the oceanic crust increases and provides additional negative buoyancy and it is at subduction zones that Earths lithosphere, oceanic crust, sedimentary layers and some trapped water are recycled into the deep mantle. Earth is so far the only planet where subduction is known to occur, subduction is the driving force behind plate tectonics, and without it, plate tectonics could not occur. Subduction zones dive down into the mantle beneath 55,000 kilometers of convergent plate margins, subduction zones burrow deeply but are imperfectly camouflaged, and geophysics and geochemistry can be used to study them. Not surprisingly, the shallowest portions of subduction zones are known best, subduction zones are strongly asymmetric for the first several hundred kilometers of their descent. They start to go down at oceanic trenches and their descents are marked by inclined zones of earthquakes that dip away from the trench beneath the volcanoes and extend down to the 660-kilometer discontinuity. Subduction zones are defined by the array of earthquakes known as the Wadati–Benioff zone after the two scientists who first identified this distinctive aspect. Subduction zone earthquakes occur at greater depths than elsewhere on Earth, such deep earthquakes may be driven by deep phase transformations, thermal runaway, the subducting basalt and sediment are normally rich in hydrous minerals and clays. Additionally, large quantities of water are introduced into cracks and fractures created as the slab bends downward
13.
Lake Toba
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Lake Toba is a large natural lake occupying the caldera of a supervolcano. The lake is about 100 kilometres long,30 kilometres wide and it is the largest lake in Indonesia and also the largest volcanic lake in the world. Lake Toba is the site of a massive supervolcanic eruption estimated at VEI8 that occurred 69,000 to 77,000 years ago and it is the largest known explosive eruption on Earth in the last 25 million years. It has been accepted that the eruption of Toba led to a winter with a worldwide decrease in temperature between 3 to 5 °C, and up to 15 °C in higher latitudes. The Toba caldera complex in Northern Sumatra, comprises four overlapping volcanic craters that adjoin the Sumatran volcanic front, the fourth and youngest caldera is the worlds largest Quaternary caldera and intersects the three older calderas. Following this eruption, a resurgent dome formed within the new caldera, at least four cones, four stratovolcanoes, and three craters are visible in the lake. The Tandukbenua cone on the edge of the caldera has only sparse vegetation. Also, the Pusubukit volcano on the edge of the caldera is solfatarically active and is a Geology Sanctuary. The Toba eruption occurred at what is now Lake Toba about 75000±900 years ago and it was the last in a series of at least four caldera-forming eruptions at this location, with earlier calderas having formed around 788000±2200 years ago. This last eruption had an estimated VEI=8, making it the largest known volcanic eruption within the last 25 million years. However, based on the new method, Toba possibly erupted 3200 km³ of ignimbrite and co-ignimbrite, the pyroclastic flows of the eruption destroyed an area of least 20,000 km2, with ash deposits as thick as 600 m by the main vent. In addition it has been calculated that 10,000 million tonnes of sulfurous acid or 6,000 million tonnes of sulfur dioxide were ejected into the atmosphere by the event. The subsequent collapse formed a caldera that, after filling with water, the island in the center of the lake is formed by a resurgent dome. The eruption lasted perhaps two weeks, and the ensuing volcanic winter resulted in a decrease in global temperatures by 3.0 to 3.5 °C for several years. Greenland ice cores record a pulse of starkly reduced levels of carbon sequestration. Very few plants or animals in southeast Asia would have survived, however, the global cooling has been discussed by Rampino and Self. Their conclusion is that the cooling had already started before Tobas eruption and this conclusion was supported by Lane and Zielinski who studied the lake-core from Africa and GISP2. They concluded that there was no volcanic winter after Toba eruption, however, this hypothesis is not widely accepted because similar effects on other animal species have not been observed, and paleoanthropology suggests there was no population bottleneck
14.
Large igneous province
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The source of many or all LIPs is variously attributed to mantle plumes or to processes associated with plate tectonics. Types of LIPs can include large volcanic provinces, created through flood basalt, rampino and Stothers cite eleven distinct flood-basalt episodes - occurring in the past 250 million years - which created volcanic provinces and plateaus and coincided with mass extinctions. However, more flood basalts have been recognized, such as the large Ontong Java Plateau, mafic, basalt sea floors and other geological products of normal plate tectonics were not included in the definition. The definition of LIP has been expanded and refined, and is still a work in progress, LIP is now frequently also used to describe voluminous areas of, not just mafic, but all types of igneous rocks. Sub-categorization of LIPs into large volcanic provinces and large plutonic provinces, Large igneous provinces are created during short-lived igneous events resulting in relatively rapid and high-volume accumulations of volcanic and intrusive igneous rock. These events warrant study because, The study of LIPs has economic implications, some workers associate them with trapped hydrocarbons. They are associated with economic concentrations of copper–nickel and iron and they are also associated with formation of major mineral provinces including Platinum-Group Element Deposits, and in the Silicic LIPs, silver and gold deposits. Titanium and vanadium deposits are found in association with LIPs. Future LIP events may pose a hazard to human civilization, LIPs in the geological record have marked major changes in the hydrosphere and atmosphere, leading to major climate shifts and maybe mass extinctions of species. Plate tectonic theory explains topography using interactions between the plates, as influenced by viscous stresses created by flow within the underlying mantle. Since the mantle is extremely viscous, the flow rate varies in pulses which are reflected in the lithosphere by small amplitude. Understanding how the interaction between mantle flow and lithosphere elevation influences formation of LIPs is important to gaining insights into past mantle dynamics, LIPs have played a major role in continental breakup, continental formation, new crustal additions from the upper mantle, and supercontinent cycles. Earth has a shell made of a number of discrete. The mantles flow is driven by the descent of cold tectonic plates during subduction, the surface of the Earth reflects stretching, thickening and bending of the tectonic plates as they interact. In this model, tectonic plates diverge at mid-ocean ridges, where hot mantle rock flows upward to fill the space, plate-tectonic processes account for the vast majority of Earths volcanism. Beyond the effects of convectively driven motion, deep processes have other influences on the surface topography, the convective circulation drives up-wellings and down-wellings in Earths mantle that are reflected in local surface levels. Hot mantle materials rising up in a plume can spread out radially beneath the tectonic plate causing regions of uplift and these ascending plumes play an important role in LIP formation. When created, LIPs often have an extent of a few million km²
15.
Volcanic ash
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Volcanic ash consists of fragments of pulverized rock, minerals and volcanic glass, created during volcanic eruptions and measuring less than 2 mm in diameter. The term volcanic ash is often loosely used to refer to all explosive eruption products. Volcanic ash is formed during volcanic eruptions when dissolved gases in magma expand. The force of the escaping gas shatters the magma and propels it into the atmosphere where it solidifies into fragments of volcanic rock and glass. Ash is also produced when magma comes into contact with water during phreatomagmatic eruptions, once in the air, ash is transported by wind up to thousands of kilometers away. Volcanic ash is formed during volcanic eruptions, phreatomagmatic eruptions. Explosive eruptions occur when magma decompresses as it rises, allowing dissolved volatiles to exsolve into gas bubbles, as more bubbles nucleate a foam is produced, which decreases the density of the magma, accelerating it up the conduit. Fragmentation occurs when bubbles occupy ~70-80 vol% of the erupting mixture, when fragmentation occurs, violently expanding bubbles tear the magma apart into fragments which are ejected into the atmosphere where they solidify into ash particles. Fragmentation is an efficient process of ash formation and is capable of generating very fine ash even without the addition of water. Volcanic ash is produced during phreatomagmatic eruptions. During these eruptions fragmentation occurs when magma comes into contact with bodies of water groundwater, as the magma, which is significantly hotter than the boiling point of water, comes into contact with water an insulating vapor film forms. Eventually this vapor film will collapse leading to direct coupling of the cold water and this increases the heat transfer which leads to the rapid expansion of water and fragmentation of the magma into small particles which are subsequently ejected from the volcanic vent. Fragmentation causes an increase in area between magma and water creating a feedback mechanism, leading to further fragmentation and production of fine ash particles. Pyroclastic density currents can also produce ash particles and these are typically produced by lava dome collapse or collapse of the eruption column. Within pyroclastic density currents particle abrasion occurs as particles interact with each resulting in a reduction in grain size. In addition, ash can be produced during secondary fragmentation of pumice fragments and these processes produce large quantities of very fine grained ash which is removed from pyroclastic density currents in co-ignimbrite ash plumes. Physical and chemical characteristics of volcanic ash are primarily controlled by the style of volcanic eruption, another parameter controlling the amount of ash produced is the duration of the eruption, the longer the eruption is sustained, the more ash will be produced. The types of minerals present in volcanic ash are dependent on the chemistry of the magma from which it erupted, low energy eruptions of basalt produce a characteristically dark coloured ash containing ~45 - 55% silica that is generally rich in iron and magnesium
16.
Climate change
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Climate change is a change in the statistical distribution of weather patterns when that change lasts for an extended period of time. Climate change may refer to a change in weather conditions. Climate change is caused by such as biotic processes, variations in solar radiation received by Earth, plate tectonics. Certain human activities have also identified as significant causes of recent climate change. Scientists actively work to understand past and future climate by using observations, more recent data are provided by the instrumental record. The most general definition of change is a change in the statistical properties of the climate system when considered over long periods of time. Accordingly, fluctuations over periods shorter than a few decades, such as El Niño, the term climate change is often used to refer specifically to anthropogenic climate change. Anthropogenic climate change is caused by activity, as opposed to changes in climate that may have resulted as part of Earths natural processes. In this sense, especially in the context of environmental policy, within scientific journals, global warming refers to surface temperature increases while climate change includes global warming and everything else that increasing greenhouse gas levels affect. A related term is climatic change, in 1966, the World Meteorological Organization proposed the term climatic change to encompass all forms of climatic variability on time-scales longer than 10 years, regardless of cause. Change was a given and climatic was used as an adjective to describe this kind of change, when it was realized that human activities had a potential to drastically alter the climate, the term climate change replaced climatic change as the dominant term to reflect an anthropogenic cause. Climate change was incorporated in the title of the Intergovernmental Panel on Climate Change, Climate change, used as a noun, became an issue rather than the technical description of changing weather. On the broadest scale, the rate at which energy is received from the Sun and this energy is distributed around the globe by winds, ocean currents, and other mechanisms to affect the climates of different regions. Factors that can shape climate are called climate forcings or forcing mechanisms, there are a variety of climate change feedbacks that can either amplify or diminish the initial forcing. Some parts of the system, such as the oceans and ice caps, respond more slowly in reaction to climate forcings. There are also key factors which when exceeded can produce rapid change. Forcing mechanisms can be internal or external. Internal forcing mechanisms are natural processes within the system itself
17.
Ice age
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An ice age is a period of long-term reduction in the temperature of Earths surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Within a long-term ice age, individual pulses of cold climate are termed glacial periods, in the terminology of glaciology, ice age implies the presence of extensive ice sheets in both northern and southern hemispheres. In 1742 Pierre Martel, an engineer and geographer living in Geneva, two years later he published an account of his journey. He reported that the inhabitants of that valley attributed the dispersal of erratic boulders to the glaciers, later similar explanations were reported from other regions of the Alps. In 1815 the carpenter and chamois hunter Jean-Pierre Perraudin explained erratic boulders in the Val de Bagnes in the Swiss canton of Valais as being due to glaciers previously extending further. An unknown woodcutter from Meiringen in the Bernese Oberland advocated a similar idea in a discussion with the Swiss-German geologist Jean de Charpentier in 1834, comparable explanations are also known from the Val de Ferret in the Valais and the Seeland in western Switzerland and in Goethes scientific work. Such explanations could also be found in parts of the world. When the Bavarian naturalist Ernst von Bibra visited the Chilean Andes in 1849–1850, meanwhile, European scholars had begun to wonder what had caused the dispersal of erratic material. From the middle of the 18th century, some discussed ice as a means of transport, the Swedish mining expert Daniel Tilas was, in 1742, the first person to suggest drifting sea ice in order to explain the presence of erratic boulders in the Scandinavian and Baltic regions. In 1795, the Scottish philosopher and gentleman naturalist, James Hutton, two decades later, in 1818, the Swedish botanist Göran Wahlenberg published his theory of a glaciation of the Scandinavian peninsula. He regarded glaciation as a regional phenomenon, only a few years later, the Danish-Norwegian geologist Jens Esmark argued a sequence of worldwide ice ages. In a paper published in 1824, Esmark proposed changes in climate as the cause of those glaciations and he attempted to show that they originated from changes in Earths orbit. During the following years, Esmarks ideas were discussed and taken over in parts by Swedish, Scottish, at the University of Edinburgh Robert Jameson seemed to be relatively open to Esmarks ideas, as reviewed by Norwegian professor of glaciology Bjørn G. Andersen. Jamesons remarks about ancient glaciers in Scotland were most probably prompted by Esmark, in Germany, Albrecht Reinhard Bernhardi, a geologist and professor of forestry at an academy in Dreissigacker, since incorporated in the southern Thuringian city of Meiningen, adopted Esmarks theory. In a paper published in 1832, Bernhardi speculated about former polar ice caps reaching as far as the zones of the globe. When he read his paper before the Schweizerische Naturforschende Gesellschaft, most scientists remained sceptical, finally, Venetz convinced his friend Jean de Charpentier. De Charpentier transformed Venetzs idea into a theory with a limited to the Alps. In fact, both men shared the same volcanistic, or in de Charpentiers case rather plutonistic assumptions, about the Earths history, in 1834, de Charpentier presented his paper before the Schweizerische Naturforschende Gesellschaft
18.
Extinction event
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An extinction event is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a change in the diversity. It occurs when the rate of extinction increases with respect to the rate of speciation, Extinction occurs at an uneven rate. Based on the record, the background rate of extinctions on Earth is about two to five taxonomic families of marine animals every million years. Marine fossils are used to measure extinction rates because of their superior fossil record. The Great Oxygenation Event was probably the first major extinction event, since the Cambrian explosion five further major mass extinctions have significantly exceeded the background extinction rate. In addition to the five mass extinctions, there are numerous minor ones as well. Mass extinctions seem to be a mainly Phanerozoic phenomenon, with extinction rates low before large complex organisms arose, estimates of the number of major mass extinctions in the last 540 million years range from as few as five to more than twenty. These differences stem from the chosen for describing an extinction event as major. In a landmark paper published in 1982, Jack Sepkoski and David M. Raup identified five mass extinctions, the Big Five cannot be so clearly defined, but rather appear to represent the largest of a relatively smooth continuum of extinction events. Cretaceous–Paleogene extinction event,66 Ma at the Cretaceous -Paleogene transition interval, the event formerly called the Cretaceous-Tertiary or K–T extinction or K-T boundary is now officially named the Cretaceous–Paleogene extinction event. About 17% of all families, 50% of all genera and 75% of all species became extinct, in the seas all the ammonites, plesiosaurs and mosasaurs disappeared and the percentage of sessile animals was reduced to about 33%. All non-avian dinosaurs became extinct during that time, the boundary event was severe with a significant amount of variability in the rate of extinction between and among different clades. Mammals and birds, the latter descended from dinosaurs, emerged as dominant large land animals. Triassic–Jurassic extinction event,201.3 Ma at the Triassic-Jurassic transition, about 23% of all families, 48% of all genera and 70% to 75% of all species became extinct. Most non-dinosaurian archosaurs, most therapsids, and most of the amphibians were eliminated. Non-dinosaurian archosaurs continued to dominate aquatic environments, while non-archosaurian diapsids continued to dominate marine environments, the Temnospondyl lineage of large amphibians also survived until the Cretaceous in Australia. Permian–Triassic extinction event,252 Ma at the Permian-Triassic transition, Earths largest extinction killed 57% of all families, 83% of all genera and 90% to 96% of all species
19.
Oruanui eruption
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The Oruanui eruption of New Zealands Taupo Volcano, the worlds most recent supereruption, had a Volcanic Explosivity Index of 8. It is one of the largest eruptions in the history of New Zealand, the eruption is divided into 10 different phases on the basis of nine mappable fall units and a tenth, poorly preserved but volumetrically dominant fall unit. Modern-day Lake Taupo partly fills the caldera generated during this eruption, a 140 km2 structural collapse is concealed beneath Lake Taupo, while the lake outline at least partly reflects volcano-tectonic collapse. Early eruption phases saw shifting vent positions, development of the caldera to its maximum extent occurred during phase 10, tephra from the eruption covered much of the central North Island, with ignimbrite up to 200 metres deep. Ashfall affected most of New Zealand, with even an 18 cm ash layer deposited on the Chatham Islands,1,000 km away. Later erosion and sedimentation had long-lasting effects on the landscape, North Island Volcanic Plateau Hatepe eruption
20.
Taupo Volcano
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Lake Taupo, in the centre of New Zealand’s North Island, is the caldera of a large rhyolitic volcano called the Taupo Volcano. This huge volcano has produced two of the world’s most violent eruptions in recent times. However, there have many more eruptions, with major ones every thousand years or so. The Taupo Volcano erupts rhyolite, a magma, with a high silica content. If the magma does not contain much gas, rhyolite tends to just form a lava dome, however, when mixed with gas or steam, rhyolitic eruptions can be extremely violent. The magma froths to form pumice and ash, which is out with great force. If the volcano creates a plume, high in the atmosphere, the pumice and ash is blown sideways. When the pumice and ash settles, it is hot to stick together as a rock called Ignimbrite. Pyroclastic flows can travel hundreds of kilometres an hour, earlier ignimbrite eruptions occurred further north than Taupo. Some of these were enormous, and two eruptions around 1.25 and 1.0 million years ago were big enough to generate an ignimbrite sheet that covered the North Island from Auckland to Napier. While Taupo has been active for 300,000 years, explosive eruptions became more common 65,000 years ago, the Oruanui eruption of the Taupo Volcano was the worlds largest known eruption in the past 70,000 years, with a Volcanic Explosivity Index of 8. Modern Lake Taupo partly fills the caldera generated during this eruption, tephra from the eruption covered much of the central North Island with ignimbrite up to 200 metres deep. Most of New Zealand was affected by ash fall, with even an 18 cm ash layer left on the Chatham Islands,1,000 km away. Later erosion and sedimentation had long-lasting effects on the landscape, the Taupo eruption represents the most recent major eruption of the Taupo Volcano, and occurred about 1,800 years ago. It represents the most violent eruption in the world in the last 5,000 years, the eruption went through several stages. A minor eruption occurred beneath the ancestral Lake Taupo, a dramatic increase in activity produced a high eruption column from a second vent, and pumice was deposited over a wide area. Water entered the first vent, and mixed with the magma, a new vent formed, and produced a dark ash- and obsidian-rich fall deposit. A larger eruption ensued, producing pumice over an area
21.
Three Sisters (Oregon)
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The Three Sisters are a complex volcano of three volcanic peaks of the Cascade Volcanic Arc and the Cascade Range in the U. S. state of Oregon. Diverse species of flora and fauna inhabit the area on and around the mountains, which is subject to frequent snowfall, occasional rain, the mountains, particularly South Sister, are popular for climbing and scrambling. Although they are grouped together and seen as one unit. Whereas North Sister is extinct and Middle Sister is dormant, South Sister last erupted about 2,000 years ago and still could erupt, threatening life within the region. After satellite imagery detected tectonic uplifting near South Sister in 2000, the three peaks, the third-, fourth-, and fifth-highest peaks in Oregon, have 15 named glaciers among them, nearly half of the 35 named glaciers in Oregon. The Sisters were named Faith, Hope, and Charity by early settlers, but these names have not prevailed, and instead they are named North Sister, Middle Sister, and South Sister. A complex volcano that extends for 20 miles, the Three Sisters are located at latitude 44. 103° N and longitude 121. 768° W. Like other Cascade volcanoes, the Three Sisters were fed by magma chambers produced by the subduction of the Juan de Fuca Plate under the edge of the North American Plate. They were also affected by the atmosphere of the Pleistocene epoch. Specifically, Three Sisters join several other volcanoes in the segment of the Cascade Range known as the High Cascades. The Three Sisters form the centerpiece of a region of closely grouped volcanic peaks and these nearby peaks include Belknap Crater, Mount Washington, Black Butte, and Three Fingered Jack to the north, and Broken Top and Mount Bachelor to the south. The region was active in the Pleistocene epoch, with eruptions between 700,000 and 170,000 years ago from an active complex known as the Tumalo volcanic center. Basaltic lava flows from North Sister overlay the newest Tumalo pyroclastic deposits, placing the age of North Sister, the Three Sisters Wilderness covers an area of 281,190 acres, making it the second-largest wilderness area in Oregon. Created by the U. S. Congress in 1964, it borders the Mount Washington Wilderness to the north, the Three Sisters Wilderness includes 260 miles of trails, in addition to many forests, lakes, waterfalls, and streams, such as the source of Whychus Creek. More specifically, the Three Sisters and Broken Top account for about a third of the Three Sisters Wilderness—an area known as the Alpine Crest Region. Rising from about 5,200 feet to 10,358 feet in elevation, it features the wilderness areas most-frequented glaciers, lakes, weather in the area varies because of separation created by the mountain barrier. The west is wetter and the east is drier, and precipitation increases with elevation, the moisture, falling mostly as winter snow, originates from warm air pockets over the Pacific Ocean and cools as it ascends the mountains. In the western section, precipitation ranges from 80 to 125 inches annually, temperature extremes reach 80 to 90 °F in summers and −20 to −30 °F during the winters
22.
Summit (topography)
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A summit is a point on a surface that is higher in elevation than all points immediately adjacent to it. Mathematically, a summit is a maximum in elevation. The topographic terms acme, apex, peak, and zenith are synonymous, the UIAA definition is that a summit is independent if it has a prominence of 30 metres or more, it is a mountain if it has a prominence of at least 300 metres. This can be summarised as follows, A pyramidal peak is an exaggerated form produced by ice erosion of a mountain top, Summit may also refer to the highest point along a line, trail, or route. In many parts of the western United States, the term refers to the highest point along a road, highway. For example, the highest point along Interstate 80 in California is referred to as Donner Summit while the highest point on Interstate 5 is Siskiyou Mountain Summit, geoid Hill List of highest mountains Maxima and minima Nadir Summit accordance Peak finder
23.
Mount Mazama
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Mount Mazama is a stratovolcano in the Oregon segment of the Cascade Volcanic Arc and the Cascade Range located in the United States. The volcanos collapsed caldera holds Crater Lake, and the mountain is located within Crater Lake National Park. Its caldera was created by an eruption 42 times greater than the one of Mount St. Helens in 1980, Mazamas summit was destroyed by a volcanic eruption that occurred around 5677 BC, ±150 years. The eruption reduced Mazamas approximate 12, 000-foot height by about 1 mile, much of the volcano fell into the volcanos partially emptied neck and magma chamber. At 8,159 feet, Hillman Peak is now the highest point on the rim, the Klamath Native Americans of the area believed that the mountain was inhabited by Llao, their god of the underworld. After the mountain destroyed itself the Klamaths recounted the events as a battle between Llao and his rival Skell, their sky god. Mazama started to grow around 400,000 years ago in the Pleistocene and these early flows averaged 20 to 30 feet thick and appear to have been emplaced over a few years to a few centuries. Several shield volcanoes were created by these flows and numerous cinder cones grew in the immediate area, more explosive eruptions started around 75,000 years ago and built a westward-trending line of composite cones. Cone building eruptions lasted until around 50,000 years ago when lava flowed down Mazamas north. Relatively few of the cone building eruptions issued from the vent, resulting in a highly complex, approximately 11, 000-foot structure made of overlapping composite cones. Consequently, Mazamas base was broader and its sides not as steep as todays Mount Shasta, after its cone building phase, Mazama lavas became increasingly silica-rich and viscous - two conditions that tend to trap explosive gases. The first major eruption in this new cycle of Mazamas life occurred about 10,000 years later and these structures were subsequently destroyed by either collapse or steam explosions. Either way, their destruction created large landslides that left deposits at the head of Munson Valley, Mazamas next major eruptive period occurred between 25,000 and 30,000 years ago and extruded rhyodacite lava. These thick, slow moving, pasty flows erupted from a vent on Mazamas northeast flank and solidified to form 600-foot high Redcloud Cliff, the volcano then went dormant for roughly the next 20,000 years, while successive ice age glaciers cut large valleys into the mountains sides. One of the largest glaciers flowed down Munson Valley near the present location of headquarters, down Annie Creek Valley. When the last ice age ended 12,000 years ago, while Mazama slept, its magma chamber was going through some differentiation, with lighter, more gas- and silica-rich rocks collecting closer to the surface. Around 5677 BC Mazama awoke from its slumber with explosive eruptions on the northern part of the main summit where Llao Rock now resides. Great quantities of pumice and ash were ejected as a crater was excavated by the explosions
24.
Howel Williams
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Howel Williams was a noted American geologist and volcanologist. He was born of Welsh parents in Liverpool, England, on October 12,1898 and he received a BA in geography in 1923 and an MA in archaeology in 1924 from Liverpool University. He studied geology at the Imperial College of Science and Technology in London, howel Williams moved to the University of California at Berkeley in 1926. In 1928 he was awarded the degree of D. Sc. from the University of Liverpool, Williams was a member of the National Academy of Sciences. He did extensive work on the geology of Central America. In Latin America, Williams put to use his early background in archeology. For instance, he used techniques to trace the origin of stone used in the giant Olmec sculptures of La Venta. Williams was a master of the art of field sketching, formerly practiced by many naturalists, many of his papers were illustrated with his meticulously done pen and ink drawings. His drawings of the features of rocks of all types were used exclusively in the very successful textbook, Petrography, by Williams, Turner. GEOLOGY OF THE MARYSVILLE BUTTES CALIFORNIA, California Geology of Tahiti, Moorea, and Maiao, 83pp Calderas and their origin, University of California Press, 346pp
25.
BBC
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The British Broadcasting Corporation is a British public service broadcaster headquartered at Broadcasting House in London, England. The total number of staff is 35,402 when part-time, flexible, the BBC is established under a Royal Charter and operates under its Agreement with the Secretary of State for Culture, Media and Sport. The fee is set by the British Government, agreed by Parliament, and used to fund the BBCs radio, TV, britains first live public broadcast from the Marconi factory in Chelmsford took place in June 1920. It was sponsored by the Daily Mails Lord Northcliffe and featured the famous Australian Soprano Dame Nellie Melba, the Melba broadcast caught the peoples imagination and marked a turning point in the British publics attitude to radio. However, this public enthusiasm was not shared in official circles where such broadcasts were held to interfere with important military and civil communications. By late 1920, pressure from these quarters and uneasiness among the staff of the licensing authority, the General Post Office, was sufficient to lead to a ban on further Chelmsford broadcasts. But by 1922, the GPO had received nearly 100 broadcast licence requests, John Reith, a Scottish Calvinist, was appointed its General Manager in December 1922 a few weeks after the company made its first official broadcast. The company was to be financed by a royalty on the sale of BBC wireless receiving sets from approved manufacturers, to this day, the BBC aims to follow the Reithian directive to inform, educate and entertain. The financial arrangements soon proved inadequate, set sales were disappointing as amateurs made their own receivers and listeners bought rival unlicensed sets. By mid-1923, discussions between the GPO and the BBC had become deadlocked and the Postmaster-General commissioned a review of broadcasting by the Sykes Committee and this was to be followed by a simple 10 shillings licence fee with no royalty once the wireless manufactures protection expired. The BBCs broadcasting monopoly was made explicit for the duration of its current broadcast licence, the BBC was also banned from presenting news bulletins before 19.00, and required to source all news from external wire services. Mid-1925 found the future of broadcasting under further consideration, this time by the Crawford committee, by now the BBC under Reiths leadership had forged a consensus favouring a continuation of the unified broadcasting service, but more money was still required to finance rapid expansion. Wireless manufacturers were anxious to exit the loss making consortium with Reith keen that the BBC be seen as a service rather than a commercial enterprise. The recommendations of the Crawford Committee were published in March the following year and were still under consideration by the GPO when the 1926 general strike broke out in May. The strike temporarily interrupted newspaper production and with restrictions on news bulletins waived the BBC suddenly became the source of news for the duration of the crisis. The crisis placed the BBC in a delicate position, the Government was divided on how to handle the BBC but ended up trusting Reith, whose opposition to the strike mirrored the PMs own. Thus the BBC was granted sufficient leeway to pursue the Governments objectives largely in a manner of its own choosing, supporters of the strike nicknamed the BBC the BFC for British Falsehood Company. Reith personally announced the end of the strike which he marked by reciting from Blakes Jerusalem signifying that England had been saved, Reith argued that trust gained by authentic impartial news could then be used
26.
Popular science
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Popular science is interpretation of science intended for a general audience. While science journalism focuses on recent scientific developments, popular science is more broad-ranging and it may be written by professional science journalists or by scientists themselves. It is presented in many forms, including books, film and television documentaries, magazine articles, Popular science is a bridge between scientific literature as a professional medium of scientific research, and the realms of popular political and cultural discourse. The goal of the genre is often to capture the methods and accuracy of science, the purpose of scientific literature is to inform and persuade peers as to the validity of observations and conclusions and the forensic efficacy of methods. Popular science attempts to inform and convince scientific outsiders of the significance of data and conclusions, by contrast, popular science emphasizes uniqueness and generality, taking a tone of factual authority absent from the scientific literature. The Literature of Science, Perspectives on Popular Scientific Writing, the University of Georgia Press, Athens,1993
27.
Horizon (BBC TV series)
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Horizon is an ongoing and long-running British documentary television series on BBC that covers science and philosophy. Horizon continues to be broadcast on BBC Two, and in 2009 added a series of films based on the rich Horizon archive called Horizon Guides on BBC Four, the future role of the BBC Horizon Editor is unclear. There have been 52 series and 1,200 episodes produced, Horizon has investigated an eclectic mix of subjects and controversial topics such as Does the MMR jab cause autism. A1978 programme about the silicon chip predicted the decline of the Swiss watch industry, in 1993, an Emmy winning episode about decreasing male fertility was given a special screening at the White House. The format of the series has varied over the years, the first ever Horizon was The World of Buckminster Fuller, produced and directed by Ramsay Short,5 February 1964. It set the style, running time 50 minutes, no in-vision presenter, interviewees speaking off camera Until the 1980s Horizon, only rare programmes had a specialist writer – in most cases the producer/director was also the writer. The first Horizon in colour was Koestler on Creativity, produced by Robert Vas,5 December 1967. Many episodes of Horizon are structured in a format that starts with a tease or menu laying out what the show has in store, followed by two acts with a plot twist around 25–35 minutes into the show. Often, episodes of Horizon end up with a montage of talking heads as experts, until early 2008, the length was standardised at 50 minutes, which was extended in the latter half of 2008 to 60 minutes. Some episodes are adapted from documentaries by other such as PBSs Nova. Horizon has also enjoyed high viewing figures, even though it covered subjects as complex as molecular biology and it has shown a change of direction since June 2006, offering a more light-hearted approach, though the subjects it covers remain serious. One programme Chimps are people too was presented by a non-scientist. Editor Andrew Cohen addressed the reasons why the programme went down this route on the Horizon web page, in October 2014, a three-part special – Cat Watch, the New Horizon Experiment – was broadcast, following up on Horizon’s 2013 The Secret Life of the Cat. Other Emmy winning programmes are, Chernobyls Sarcophagus, Assault on the Male, in 1988, Horizon won a BAFTA for Best Drama, Life Story, another in 1996 for Best Documentary, Fermats Last Theorem and another in 2001 for Best Factual Series or Strand. Three Horizon episodes were included on The Wonders Collection Special Edition DVD, the episodes were Do You Know What Time It Is. Can We Make A Star On Earth, and What on Earth is Wrong With Gravity
28.
Caldera
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A caldera is a large cauldron-like depression that forms following the evacuation of a magma chamber/reservoir. When large volumes of magma are erupted over a time period. The ground surface then collapses downward into the emptied magma chamber. Although sometimes described as a crater, the feature is actually a type of sinkhole, as it is formed through subsidence, only seven known caldera-forming collapses have occurred since the start of the 20th century, most recently at Bárðarbunga volcano in Iceland. The word comes from Spanish caldera, and this from Latin caldaria, in some texts the English term cauldron is also used. If enough magma is ejected, the chamber is unable to support the weight of the volcanic edifice above it. A roughly circular fracture, the fault, develops around the edge of the chamber. Ring fractures serve as feeders for fault intrusions which are known as ring dykes. Secondary volcanic vents may form above the ring fracture, as the magma chamber empties, the center of the volcano within the ring fracture begins to collapse. The collapse may occur as the result of a cataclysmic eruption. The total area that collapses may be hundreds or thousands of square kilometers, some calderas are known to host rich ore deposits. One of the worlds best-preserved mineralized calderas is the Sturgeon Lake Caldera in northwestern Ontario, Canada, if the magma is rich in silica, the caldera is often filled in with ignimbrite, tuff, rhyolite, and other igneous rocks. Silica-rich magma has a high viscosity, and therefore does not flow easily like basalt, as a result, gases tend to become trapped at high pressure within the magma. Further lava flows may be erupted, if volcanic activity continues, the center of the caldera may be uplifted in the form of a resurgent dome such as is seen at Cerro Galán, Lake Toba, Yellowstone, etc. by subsequent intrusion of magma. A silicic or rhyolitic caldera may erupt hundreds or even thousands of kilometers of material in a single event. Even small caldera-forming eruptions, such as Krakatoa in 1883 or Mount Pinatubo in 1991, may result in significant local destruction, large calderas may have even greater effects. When Yellowstone Caldera last erupted some 650,000 years ago, it released about 1,000 km3 of material, by comparison, when Mount St. Helens erupted in 1980, it released ~1.2 km3 of ejecta. The ecological effects of the eruption of a large caldera can be seen in the record of the Lake Toba eruption in Indonesia, more recently several geneticists, including Lynn Jorde and Henry Harpending have proposed that the human species was reduced to approximately five to ten thousand people
29.
Blake River Megacaldera Complex
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The Blake River Megacaldera Complex is a giant subaqueous caldera cluster or a nested caldera system that spans across the Ontario-Quebec border in Canada. The caldera complex is around 2.7 billion years old and it lies within the southern zone of the Abitibi greenstone belt of the Superior craton and has an area of 3,000 km2. The Blake River Megacaldera Complex has been a centre of major interest since 2006 with numerous excursions at the international, national and local level and it is a world-class metallotect with respect to both hydrothermal Cu-Zn massive sulfides and gold-rich massive sulfides. The first phase resulted in the creation of the 80 km long,40 km wide and it is a coalescence of at least two large mafic shield volcanoes that formed more than 2703 million years ago. The second phase resulted in the creation of the 30 km long,15 km wide and its formation consists of thick massive mafic sequences which has inferred to be a subaqueous lava lake during the early stages of the calderas development. The Blake River Megacaldera Complex is considered a supervolcano due to its size and its multiple dikes. As a result, the Blake River Group is best categorized as a caldera complex. List of volcanoes in Canada Volcanism of Canada Volcanism of Eastern Canada
30.
Ontario
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Ontario, one of the 13 provinces and territories of Canada, is located in east-central Canada. It is Canadas most populous province by a margin, accounting for nearly 40 percent of all Canadians. Ontario is fourth-largest in total area when the territories of the Northwest Territories and it is home to the nations capital city, Ottawa, and the nations most populous city, Toronto. There is only about 1 km of land made up of portages including Height of Land Portage on the Minnesota border. Ontario is sometimes divided into two regions, Northern Ontario and Southern Ontario. The great majority of Ontarios population and arable land is located in the south, in contrast, the larger, northern part of Ontario is sparsely populated with cold winters and is heavily forested. The province is named after Lake Ontario, a thought to be derived from Ontarí, io, a Huron word meaning great lake, or possibly skanadario. Ontario has about 250,000 freshwater lakes, the province consists of three main geographical regions, The thinly populated Canadian Shield in the northwestern and central portions, which comprises over half the land area of Ontario. Although this area mostly does not support agriculture, it is rich in minerals and in part covered by the Central and Midwestern Canadian Shield forests, studded with lakes, Northern Ontario is subdivided into two sub-regions, Northwestern Ontario and Northeastern Ontario. The virtually unpopulated Hudson Bay Lowlands in the north and northeast, mainly swampy. Southern Ontario which is further sub-divided into four regions, Central Ontario, Eastern Ontario, Golden Horseshoe, the highest point is Ishpatina Ridge at 693 metres above sea level located in Temagami, Northeastern Ontario. In the south, elevations of over 500 m are surpassed near Collingwood, above the Blue Mountains in the Dundalk Highlands, the Carolinian forest zone covers most of the southwestern region of the province. A well-known geographic feature is Niagara Falls, part of the Niagara Escarpment, the Saint Lawrence Seaway allows navigation to and from the Atlantic Ocean as far inland as Thunder Bay in Northwestern Ontario. Northern Ontario occupies roughly 87 percent of the area of the province. Point Pelee is a peninsula of Lake Erie in southwestern Ontario that is the southernmost extent of Canadas mainland, Pelee Island and Middle Island in Lake Erie extend slightly farther. All are south of 42°N – slightly farther south than the border of California. The climate of Ontario varies by season and location, the effects of these major air masses on temperature and precipitation depend mainly on latitude, proximity to major bodies of water and to a small extent, terrain relief. In general, most of Ontarios climate is classified as humid continental, Ontario has three main climatic regions
31.
Quebec
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Quebec is the second-most populous province of Canada and the only one to have a predominantly French-speaking population, with French as the sole provincial official language. Quebec is Canadas largest province by area and its second-largest administrative division and it also shares maritime borders with Nunavut, Prince Edward Island, and Nova Scotia. Quebec is Canadas second-most populous province, after Ontario, most inhabitants live in urban areas near the Saint Lawrence River between Montreal and Quebec City, the capital. Approximately half of Quebec residents live in the Greater Montreal Area, the Nord-du-Québec region, occupying the northern half of the province, is sparsely populated and inhabited primarily by Aboriginal peoples. Even in central Quebec at comparatively southerly latitudes winters are severe in inland areas, Quebec independence debates have played a large role in the politics of the province. Parti Québécois governments held referendums on sovereignty in 1980 and 1995, in 2006, the House of Commons of Canada passed a symbolic motion recognizing the Québécois as a nation within a united Canada. These many industries have all contributed to helping Quebec become an economically influential province within Canada, early variations in the spelling of the name included Québecq and Kébec. French explorer Samuel de Champlain chose the name Québec in 1608 for the colonial outpost he would use as the seat for the French colony of New France. The province is sometimes referred to as La belle province, the Province of Quebec was founded in the Royal Proclamation of 1763 after the Treaty of Paris formally transferred the French colony of Canada to Britain after the Seven Years War. The proclamation restricted the province to an area along the banks of the Saint Lawrence River, the Treaty of Versailles ceded territories south of the Great Lakes to the United States. After the Constitutional Act of 1791, the territory was divided between Lower Canada and Upper Canada, with each being granted an elected legislative assembly, in 1840, these become Canada East and Canada West after the British Parliament unified Upper and Lower Canada into the Province of Canada. This territory was redivided into the Provinces of Quebec and Ontario at Confederation in 1867, each became one of the first four provinces. In 1898, the Canadian Parliament passed the first Quebec Boundary Extension Act that expanded the provincial boundaries northward to include the lands of the aboriginal peoples. This was followed by the addition of the District of Ungava through the Quebec Boundaries Extension Act of 1912 that added the northernmost lands of the Inuit to create the modern Province of Quebec. In 1927, the border between Quebec and Newfoundland and Labrador was established by the British Judicial Committee of the Privy Council. Located in the part of Canada, and part of Central Canada. Its topography is very different from one region to another due to the composition of the ground, the climate. The Saint Lawrence Lowland and the Canadian Shield are the two main regions, and are radically different
32.
Geology of Iceland
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The geology of Iceland is unique and of particular interest to geologists. Iceland lies on the divergent boundary between the Eurasian plate and the North American plate. It also lies above a hotspot, the Iceland plume, which is believed to have caused the formation of Iceland itself, the result is an island characterised by repeated volcanism and geothermal phenomena such as geysers. This caused crop failures in Europe and may have caused droughts in India, the eruption has been estimated to have killed over six million people globally, making it one of the deadliest volcanoes, with Tambora being number one. In the period 1965 to 1969 the new island of Surtsey was created on the southwest coast by a volcanic eruption and these Pliocene and late Pleistocene deposits are composed of silt and sandstones, with fossils preserved in the lower layers. The primary fossil types found in the Tjörnes beds are marine mollusc shells, vegetational changes Past climate Origin of the strata Fossil preservation The tectonic structure of Iceland is characterized by various seismically and volcanically active centers. Iceland is bordered to the south by the Reykjanes Ridge segment of the Mid-Atlantic Ridge, rifting in the southern part of Iceland is focused in two main parallel rift zones. The Reykjanes Peninsula Rift in SW Iceland is the continuation of the Reykjanes Ridge that connects to the Western Volcanic Zone. The more active Eastern Volcanic Zone represents a rift jump, although it is unclear how the propagation of the main rifting activity has occurred. The offset between the WVZ and the EVZ is accommodated by the South Iceland Seismic Zone, a characterized by high earthquake activity. The EVZ transitions northward into the Northern Volcanic Zone, which contains Krafla volcano, the NVZ is connected to the Kolbeinsey Ridge by the Tjörnes Fracture Zone, another major center of seismicity and deformation. Glaciers cover approximately 11% of Iceland, the largest of which is Vatnajökull, as many glaciers overlie active volcanoes, subglacial eruptions can pose hazards due to sudden floods produced by glacial meltwater, known as jökulhlaups. Icelandic glaciers have generally been retreating over the past 100 years, with Vatnajökull having lost as much as 10% of its volume. G
33.
Siberian Traps
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The Siberian Traps form a large region of volcanic rock, known as a large igneous province, in Siberia, Russia. The term traps is derived from the Swedish word for stairs, referring to the hills forming the landscape of the region. Vast volumes of lava covered a large expanse of Siberia in a flood basalt event. Today the area covered is about 2 million square kilometres —roughly equal to western Europe in land area—and estimates of the original coverage are as high as 7 million square kilometres, the original volume of lava is estimated to range from 1 to 4 million cubic kilometres. The area covered lies between latitude 50° and 75° north and longitude 60° to 120° east, another possible cause may be the impact that formed the Wilkes Land crater, which may have been contemporaneous and would have been nearly antipodal to the Traps. This controversial scientific debate is ongoing, the Siberian Traps are considered to have erupted via numerous vents over a period of roughly a million years or more, probably east and south of Norilsk in Siberia. Individual eruptions of basalt lavas could have exceeded 2000 km3, the presence of extensive tuff and pyroclastic deposits suggests that a number of large explosive eruptions occurred during or before the eruptions of basaltic lavas. The presence of volcanic rocks such as rhyolite is also indicative of explosive eruptions. This massive eruptive event spanned the Permian-Triassic boundary, about 250 million years ago, one of the major questions is whether the Siberian Traps were directly responsible, or if they were themselves caused by some other, larger event, such as an asteroid impact. This extinction event, also called the Great Dying, affected all life on Earth, life on land took at least 30 million years to fully recover from the environmental disruptions which may have been caused by the eruption of the Siberian Traps. Calculations of sea temperature from δ18O measurements indicate that at its peak. The tetrapod gap of equatorial Pangea coincides with an end-Permian to Middle Triassic global coal gap that indicates the loss of peat swamps, the giant Norilsk-Talnakh nickel–copper–palladium deposit formed within the magma conduits in the main part of the Siberian Traps. Deccan Traps Emeishan Traps Viluy Traps The Siberian Traps by Richard Cowen The Siberian Traps Large Igneous Province Toxic Gases Caused Worlds Worst Mass Extinction
34.
Deccan Traps
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The Deccan Traps are a large igneous province located on the Deccan Plateau of west-central India and one of the largest volcanic features on Earth. They consist of layers of solidified flood basalt that together are more than 2,000 m thick, cover an area of c.500,000 km2. Originally, the Deccan Traps may have covered c.1,500,000 km2, the term trap has been used in geology since 1785–95 for such rock formations. It is derived from the Scandinavian word for stairs and refers to the hills forming the landscape of the region. The Deccan Traps began forming 66.25 million years ago, the bulk of the volcanic eruption occurred at the Western Ghats some 66 million years ago. This series of eruptions may have lasted less than 30,000 years in total, the original area covered by the lava flows is estimated to have been as large as 1.5 million km², approximately half the size of modern India. The Deccan Traps region was reduced to its current size by erosion and plate tectonics, the release of volcanic gases, particularly sulphur dioxide, during the formation of the traps contributed to contemporary climate change. Data points to a drop in temperature of 2 °C in this period. Because of its magnitude, scientists formerly speculated that the released during the formation of the Deccan Traps played a role in the Cretaceous–Paleogene extinction event. However, the current consensus among the community is that the extinction was triggered by the Chicxulub impact event in North America. Work published in 2014 by geologist Gerta Keller and others on the timing of the Deccan volcanism suggests the extinction may have been caused by both the volcanism and the impact event and this was followed by a similar study in 2015. Within the Deccan Traps at least 95% of the lavas are tholeiitic basalts, however, other rock types do occur, Alkali basalts Nephelinites Lamprophyre Carbonatites Mantle xenoliths have been described from Kachchh and elsewhere in the western Deccan. The Deccan Traps are famous for the beds of fossils that have found between layers of lava. The infratrappean and intertrappean beds also contain fossil freshwater mollusks and it is postulated that the Deccan Traps eruption was associated with a deep mantle plume. The area of long-term eruption, known as the Réunion hotspot, is suspected of causing the Deccan Traps eruption and opening the rift that once separated the Seychelles plateau from India. Seafloor spreading at the boundary between the Indian and African Plates subsequently pushed India north over the plume, which now lies under Réunion island in the Indian Ocean, the mantle plume model has, however, been challenged. Data continues to emerge which supports the plume model, the motion of the Indian tectonic plate and the eruptive history of the Deccan traps show strong correlations. Based on data from marine magnetic profiles, a pulse of unusually rapid plate motion begins at the time as the first pulse of Deccan flood basalts
35.
Basalt
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Basalt is a common extrusive igneous rock formed from the rapid cooling of basaltic lava exposed at or very near the surface of a planet or moon. Flood basalt describes the formation in a series of basalt flows. By definition, basalt is an igneous rock with generally 45-55% silica and less than 10% feldspathoid by volume. Basalt commonly features a very fine-grained or glassy matrix interspersed with visible mineral grains, the average density is 3.0 gm/cm3. Basalt is defined by its content and texture, and physical descriptions without mineralogical context may be unreliable in some circumstances. Basalt is usually grey to black in colour, but rapidly weathers to brown or rust-red due to oxidation of its mafic minerals into hematite, although usually characterized as dark, basaltic rocks exhibit a wide range of shading due to regional geochemical processes. Due to weathering or high concentrations of plagioclase, some basalts can be quite light-coloured and these phenocrysts usually are of olivine or a calcium-rich plagioclase, which have the highest melting temperatures of the typical minerals that can crystallize from the melt. Basalt with a texture is called vesicular basalt, when the bulk of the rock is mostly solid. Gabbro is often marketed commercially as black granite and these ultramafic volcanic rocks, with silica contents below 45% are usually classified as komatiites. Agricola applied basalt to the black rock of the Schloßberg at Stolpen. Tholeiitic basalt is relatively rich in silica and poor in sodium, included in this category are most basalts of the ocean floor, most large oceanic islands, and continental flood basalts such as the Columbia River Plateau. Basalt rocks are in some cases classified after their content in High-Ti and Low-Ti varieties. High-Ti and Low-Ti basalts have been distinguished in the Paraná and Etendeka traps and it has greater than 17% alumina and is intermediate in composition between tholeiite and alkali basalt, the relatively alumina-rich composition is based on rocks without phenocrysts of plagioclase. Alkali basalt is relatively poor in silica and rich in sodium and it is silica-undersaturated and may contain feldspathoids, alkali feldspar and phlogopite. Boninite is a form of basalt that is erupted generally in back-arc basins. Ocean island basalt Lunar basalt On Earth, most basalt magmas have formed by melting of the mantle. Basalt commonly erupts on Io, the third largest moon of Jupiter, and has formed on the Moon, Mars, Venus. The crustal portions of oceanic tectonic plates are composed predominantly of basalt, produced from upwelling mantle below, the mineralogy of basalt is characterized by a preponderance of calcic plagioclase feldspar and pyroxene
36.
Flood basalt
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A flood basalt is the result of a giant volcanic eruption or series of eruptions that coats large stretches of land or the ocean floor with basalt lava. Flood basalt provinces such as the Deccan Traps of India are often called traps, rampino and Stothers cite eleven distinct flood basalt episodes occurring in the past 250 million years, creating large volcanic provinces, plateaus, and mountain ranges. However, more have been recognized such as the large Ontong Java Plateau, Large igneous provinces have been connected to five mass extinction events, and may be associated with bolide impacts. These have a low viscosity, which is why they flood rather than form taller volcanoes. Another explanation is that they result from the release, over a time period. The Deccan Traps of central India, the Siberian Traps, the Mesoproterozoic Mackenzie Large Igneous Province in Canada contains the Coppermine River flood basalts related to the Muskox layered intrusion. The maria on the Moon are additional, even more extensive, flood basalts on the ocean floor produce oceanic plateaus. The surface covered by one eruption can vary from around 200,000 km² to 1,500,000 km², the thickness can vary from 2000 metres to 12,000 m. These are smaller than the original due to erosion. Flood basalts have tholeiite and olivine compositions, the composition of the basalts from the Paraná is fairly typical of that of flood basalts, it contains phenocrysts occupying around 25% of the volume of rock in a fine-grained matrix. These phenocrysts are pyroxenes, plagioclases, opaque crystals such as titanium rich magnetite or ilmenite, sometimes more differentiated volcanic products such as andesites, dacites and rhyodacites have been observed, but only in small quantities at the top of former magma chambers. Subaerial flood basalts can be of two kinds, with a smooth or twisted surface, very compact surface, vesicles are rare, such lava flows may form underground rivers, when degassing fractures and conduits are present, very large flows may reach the surface. With a chaotic surface, the flood is very rich in bubbles of gas, with an irregular. In the Massif Central in Auvergne, France, there is an example of chaotic lava flow, produced by eruptions from Puy de la Vache. Geochemical analysis of the major oxides reveals a close to that of mid-ocean ridge basalts. These are in fact tholeiites with a silicon dioxide percentage close to 50% and it is this contamination that explains the difference between the two kinds of basalt mentioned above. The low phosphorus and titanium type has an excess of elements from the crust such as potassium and strontium, the content in incompatible elements of flood basalts is lower than that of ocean island basalts, but higher than that of mid-ocean ridge basalts. Basalt floods on the planet Venus are larger than those on Earth. S, magmatism at rift zones, The generation of volcanic continental margins and flood basalts
37.
Meteor
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A meteoroid is a small rocky or metallic body in outer space. Meteoroids are significantly smaller than asteroids, and range in size from small grains to 1 meter-wide objects, objects smaller than this are classified as micrometeoroids or space dust. Most are fragments from comets or asteroids, whereas others are collision impact debris ejected from bodies such as the Moon or Mars and this phenomenon is called a meteor or shooting star. A series of many meteors appearing seconds or minutes apart and appearing to originate from the fixed point in the sky is called a meteor shower. If that object withstands ablation from its passage through the atmosphere as a meteor and impacts with the ground, an estimated 15,000 tonnes of meteoroids, micrometeoroids and different forms of space dust enter Earths atmosphere each year. In 1995, Beech and Steel, writing in the Quarterly Journal of the Royal Astronomical Society, according to Rubin and Grossman, the minimum size of an asteroid is given by what can be discovered from Earth-bound telescopes, so the distinction between meteoroid and asteroid is fuzzy. Some of the smallest asteroids discovered are 2008 TS26 with H =33.2 and 2011 CQ1 with H =32.1 both with a size of 1 meter. Objects smaller than meteoroids are classified as micrometeoroids and cosmic dust, the Minor Planet Center does not use the term meteoroid. Almost all meteoroids contain extraterrestrial nickel and iron and they have three main classifications, iron, stone, and stony-iron. Some stone meteoroids contain grain-like inclusions known as chondrules and are called chondrites, stoney meteoroids without these features are called achondrites, which are typically formed from extraterrestrial igneous activity, they contain little or no extraterrestrial iron. The composition of meteoroids can be inferred as they pass through Earths atmosphere from their trajectories and their effects on radio signals also give information, especially useful for daytime meteors, which are otherwise very difficult to observe. From these trajectory measurements, meteoroids have been found to have many different orbits, some clustering in streams associated with a parent comet. Debris from meteoroid streams may eventually be scattered into other orbits, the study of meteorites also gives insights into the composition of non-ephemeral meteoroids. Most meteoroids come from the belt, having been perturbed by the gravitational influences of planets. Some meteoroids are pieces of planets or moons, such as Mars or our moon, meteoroids travel around the Sun in a variety of orbits and at various velocities. The fastest ones move at about 42 kilometers per second through space in the vicinity of Earths orbit, Earth travels at about 29.6 kilometers per second. Thus, when meteoroids meet Earths atmosphere head-on, the speed may reach about 71 kilometers per second. Meteoroids moving through Earths orbital space average about 20 km/s, on January 17,2013 at 05,21 PST, a 1 meter-sized comet from the Oort cloud entered Earth atmosphere over a wide area in California and Nevada
38.
Lava fountain
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Lava is the molten rock expelled by a volcano during an eruption. The resulting rock after solidification and cooling is called lava. The molten rock is formed in the interior of planets, including Earth. The source of the heat melts the rock within the earth is geothermal energy. When first erupted from a vent, lava is a liquid usually at temperatures from 700 to 1,200 °C. A lava flow is an outpouring of lava, which is created during a non-explosive effusive eruption. When it has stopped moving, lava solidifies to form igneous rock, the term lava flow is commonly shortened to lava. Although lava can be up to 100,000 times more viscous than water, lava can flow great distances before cooling and solidifying because of its thixotropic, explosive eruptions produce a mixture of volcanic ash and other fragments called tephra, rather than lava flows. The word lava comes from Italian, and is derived from the Latin word labes which means a fall or slide. The first use in connection with extruded magma was apparently in an account written by Francesco Serao on the eruption of Vesuvius between May 14 and June 4,1737. Serao described a flow of lava as an analogy to the flow of water. The composition of almost all lava of the Earths crust is dominated by silicate minerals, mostly feldspars, olivine, pyroxenes, amphiboles, micas, igneous rocks, which form lava flows when erupted, can be classified into three chemical types, felsic, intermediate, and mafic. These classes are primarily chemical, however, the chemistry of lava also tends to correlate with the temperature, its viscosity. Felsic or silicic lavas such as rhyolite and dacite typically form lava spines, most silicic lava flows are extremely viscous, and typically fragment as they extrude, producing blocky autobreccias. Felsic magmas can erupt at temperatures as low as 650 to 750 °C, unusually hot rhyolite lavas, however, may flow for distances of many tens of kilometres, such as in the Snake River Plain of the northwestern United States. Intermediate or andesitic lavas are lower in aluminium and silica, and usually somewhat richer in magnesium, intermediate lavas form andesite domes and block lavas, and may occur on steep composite volcanoes, such as in the Andes. Poorer in aluminium and silica than felsic lavas, and also commonly hotter, greater temperatures tend to destroy polymerized bonds within the magma, promoting more fluid behaviour and also a greater tendency to form phenocrysts. Higher iron and magnesium tends to manifest as a darker groundmass, mafic or basaltic lavas are typified by their high ferromagnesian content, and generally erupt at temperatures in excess of 950 °C
39.
Iceland
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Iceland is a Nordic island country in the North Atlantic Ocean. It has a population of 332,529 and an area of 103,000 km2, the capital and largest city is Reykjavík. Reykjavík and the areas in the southwest of the country are home to over two-thirds of the population. Iceland is volcanically and geologically active, the interior consists of a plateau characterised by sand and lava fields, mountains and glaciers, while many glacial rivers flow to the sea through the lowlands. Iceland is warmed by the Gulf Stream and has a climate, despite a high latitude just outside the Arctic Circle. Its high latitude and marine influence still keeps summers chilly, with most of the archipelago having a tundra climate. According to the ancient manuscript Landnámabók, the settlement of Iceland began in the year 874 AD when the Norwegian chieftain Ingólfr Arnarson became the first permanent settler on the island. In the following centuries, Norwegians, and to a lesser extent other Scandinavians, emigrated to Iceland, the island was governed as an independent commonwealth under the Althing, one of the worlds oldest functioning legislative assemblies. Following a period of strife, Iceland acceded to Norwegian rule in the 13th century. The establishment of the Kalmar Union in 1397 united the kingdoms of Norway, Denmark, Iceland thus followed Norways integration to that Union and came under Danish rule after Swedens secession from that union in 1523. In the wake of the French revolution and the Napoleonic wars, Icelands struggle for independence took form and culminated in independence in 1918, until the 20th century, Iceland relied largely on subsistence fishing and agriculture, and was among the poorest in Europe. Industrialisation of the fisheries and Marshall Plan aid following World War II brought prosperity, in 1994, it became a part of the European Economic Area, which further diversified the economy into sectors such as finance, biotechnology, and manufacturing. Iceland has an economy with relatively low taxes compared to other OECD countries. It maintains a Nordic social welfare system that provides health care. Iceland ranks high in economic, political and social stability and equality, in 2013, it was ranked as the 13th most-developed country in the world by the United Nations Human Development Index. Iceland runs almost completely on renewable energy, some bankers were jailed, and the economy has made a significant recovery, in large part due to a surge in tourism. Icelandic culture is founded upon the nations Scandinavian heritage, most Icelanders are descendants of Germanic and Gaelic settlers. Icelandic, a North Germanic language, is descended from Old Norse and is related to Faroese
40.
Laki fissure
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Laki or Lakagígar is a volcanic fissure in the south of Iceland, not far from the canyon of Eldgjá and the small village of Kirkjubæjarklaustur. Lakagígar is the name, as Laki mountain itself did not erupt. Lakagígar is part of a system centered on the volcano Grímsvötn. It lies between the glaciers of Mýrdalsjökull and Vatnajökull, in an area of fissures that run in a southwest to northeast direction and this led to a famine which then killed approximately 25% of the islands human population. The lava flows also destroyed 20 villages The Laki eruption and its caused a drop in global temperatures. This caused crop failures in Europe and may have caused droughts in North Africa, on 8 June 1783, a 25 km long fissure with 130 craters opened with phreatomagmatic explosions because of the groundwater interacting with the rising basalt magma. Over a few days the eruptions became less explosive, Strombolian, the eruption, also known as the Skaftáreldar or Síðueldur, produced an estimated 14 km3 of basalt lava, and the total volume of tephra emitted was 0.91 km3. Lava fountains were estimated to have reached heights of 800 to 1,400 m, the gases were carried by the convective eruption column to altitudes of about 15 km. The eruption continued until 7 February 1784, but most of the lava was ejected in the first five months, Grímsvötn volcano, from which the Laki fissure extends, was also erupting at the time, from 1783 until 1785. The consequences for Iceland, known as the Móðuharðindin Mist Hardships, were disastrous, an estimated 20–25% of the population died in the famine and fluoride poisoning after the fissure eruptions ensued. Around 80% of sheep, 50% of cattle and 50% of horses died because of dental fluorosis, the parish priest and dean of Vestur-Skaftafellssýsla, Jón Steingrímsson, grew famous because of the eldmessa that he delivered on 20 July 1783. This past week, and the two prior to it, more poison fell from the sky than words can describe, ash, volcanic hairs, rain full of sulfur and saltpeter, all of it mixed with sand. The snouts, nostrils, and feet of livestock grazing or walking on the grass turned bright yellow, all water went tepid and light blue in color and gravel slides turned gray. All the earths plants burned, withered and turned gray, one after another, the resulting famine that afflicted Egypt in 1784 cost it roughly one-sixth of its population. The eruption was also found to have affected the southern Arabian Peninsula, the summer of 1783 was the hottest on record and a rare high-pressure zone over Iceland caused the winds to blow to the south-east. The fog was so thick that boats stayed in port, unable to navigate, inhaling sulphur dioxide gas causes victims to choke as their internal soft tissue swells – the gas reacts with the moisture in lungs and produces sulfurous acid. The local death rate in Chartres was up by 5% during August and September and it has been estimated that 23,000 British people died from the poisoning. The weather became very hot, causing severe thunderstorms with large hailstones that were reported to have killed cattle, the winter of 1783–1784 was very severe, the naturalist Gilbert White in Selborne, Hampshire, reported 28 days of continuous frost
41.
Hikurangi Plateau
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The Hikurangi Plateau is an oceanic plateau in the South Pacific Ocean east of the North Island of New Zealand. It is part of a large igneous province together with Manihiki and Ontong Java, mount Hikurangi, in Māori mythology the first part of North Island to emerge from the ocean, gave its name to the plateau. The Hikurangi Plateau covers approximately 400,000 km2 and reaches 2, two models have been proposed for the formation of Hikurangi. It can be derived from the mantle plume that caused the break-up of Gondwana, a 2010 study of isotopic data supported the mega-plateau or Greater Ontong Java Event model. There are, nevertheless, traces in seamounts on Hikurangi of a second Late Cretaceous magmatic event contemporaneous with volcanism on New Zealand and associated with the final break-up of Gondwana. The Hikurangi Plateau has been subducted under the Chatham Rise, probably during the Cretaceous. The western margin of the plateau is actively subducting under the North Island of New Zealand to a depth of 65 km. With these missing portions of the added to it, the Hikurangi Plateau originally must have covered 800,000 km2. These subducted parts are reaching 37–140 km into the mantle beneath the North Island, the extent of the Hikurangi Plateau slab suggests that it has played a significant role in the geology of New Zealand during the past 100 Ma. The Southern Alps in central South Island are being uplifted along the plate boundary there, the Australian and Pacific plates converge obliquely in the Tonga-Kermadec-Hikurangi subduction zone.8 Mw 1931 Hawkes Bay earthquake. Campbell Plateau Hikurangi Trench Large low-shear-velocity provinces Tonga-Kermadec Ridge
42.
World's largest eruptions
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In a volcanic eruption, lava, tephra, and various gases are expelled from a volcanic vent or fissure. Volcanic eruptions can generally be characterized as either explosive eruptions, sudden ejections of rock and ash, or effusive eruptions, a separate list is given below for each type. All of the eruptions listed below have produced at least 1,000 km3 of lava and tephra, for explosive eruptions and they are at least a thousand times larger than the 1980 eruption of Mount St. There have probably been many such eruptions during Earths history beyond those shown in these lists, however erosion and plate tectonics have taken their toll, and many eruptions have not left enough evidence for geologists to establish their size. Even for the eruptions listed here, estimates of the volume erupted can be subject to considerable uncertainty, in explosive eruptions, the eruption of magma is driven by the rapid release of pressure, often involving the explosion of gas previously dissolved within the material. The most famous and destructive historical eruptions are mainly of this type, an eruptive phase can consist of a single eruption, or a sequence of several eruptions spread over several days, weeks or months. Explosive eruptions usually involve thick, highly viscous, silicic or felsic magma, high in volatiles like water vapor, pyroclastic materials are the primary product, typically in the form of tuff. Effusive eruptions involve a relatively gentle, steady outpouring of lava rather than large explosions and they can continue for years or decades, producing extensive fluid mafic lava flows. For example, Kīlauea on Hawaiʻi has continued erupting from 1983 to the present, the ensuing disruptions to the climate may also have killed millions elsewhere.000 years. The lava fields of these eruptions measure 565 km2,700 km2 and 950 km2, highly active periods of volcanism in what are called large igneous provinces have produced huge oceanic plateaus and flood basalts in the past. These can comprise hundreds of large eruptions, producing millions of kilometers of lava in total. No large eruptions of flood basalts have occurred in human history and they are often associated with breakup of supercontinents such as Pangea in the geologic record, and may have contributed to a number of mass extinctions. Most large igneous provinces have either not been studied enough to establish the size of their component eruptions. Many of the eruptions listed above thus come from just two large provinces, the Paraná and Etendeka traps and the Columbia River Basalt Group. The latter is the most recent large igneous province, and also one of the smallest, a list of large igneous provinces follows to provide some indication of how many large eruptions may be missing from the lists given here. Extinction event Lists of earthquakes List of impact craters on Earth Supervolcano#Massive explosive eruptions Types of eruptions List of Flood basalt provinces
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Logarithmic scale
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A logarithmic scale is a nonlinear scale used when there is a large range of quantities. Common uses include the strength, sound loudness, light intensity. It is based on orders of magnitude, rather than a linear scale. In particular our sense of hearing perceives equal ratios of frequencies as equal differences in pitch, the top left graph is linear in the X and Y axis, and the Y-axis ranges from 0 to 10. A base-10 log scale is used for the Y axis of the left graph. The top right graph uses a scale for just the X axis. A slide rule has logarithmic scales, and nomograms often employ logarithmic scales, the geometric mean of two numbers is midway between the numbers. Before the advent of graphics, logarithmic graph paper was a commonly used scientific tool. If both the vertical and horizontal axes of a plot are scaled logarithmically, the plot is referred to as a log–log plot, if only the ordinate or abscissa is scaled logarithmically, the plot is referred to as a semi-logarithmic plot. Bit Byte Decade John Napier Level Logarithm Logarithmic mean Preferred number Dehaene, Stanislas, Izard, Véronique, Spelke, Elizabeth, Pica, distinct intuitions of the number scale in Western and Amazonian indigene cultures. American Association for the Advancement of Science, why using logarithmic scale to display share prices
