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CREATION ART

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  • Photobucket Songs of Earth's Creations. In an endless cycle of eons she creates and destroys masterpieces, reusing her building materials to create anew. From death comes life.Photobucket
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    Tuesday, November 20, 2007

     

    Ayers Rock and Geological "Monoliths" (a misnomer)

    This IKONOS satellite image of Ayers Rock was collected Jan. 17, 2004. Ayers Rock is located in Kata Tjuta National Park, 280 miles (450km) southwest of Alice Springs, Australia. It is reputed to be the world's largest monolith, an Aboriginal sacred site and Australia's most famous natural landmark.

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    http://en.wikipedia.org/wiki/Ayers_Rock

    Uluru

    From Wikipedia, the free encyclopedia

    (Redirected from Ayers Rock)

    Coordinates: 25°20′42″S 131°02′10″E / -25.345, 131.03611
    Uluṟu
    Ayers Rock
    Mountain
    Uluṟu at sunset
    Country Flag of Australia Australia
    State Northern Territory

    Elevation 863 m (2,831 ft)
    Coordinates 25°20′42″S 131°02′10″E / -25.345, 131.03611

    Geology arkose
    Orogeny Petermann

    UNESCO World Heritage Site
    Name Uluṟu - Kata Tjuṯa National Park







    Location in Australia
    Location in Australia
    Location in Australia
    Wikimedia Commons: Uluru
    Website: www.environment.gov.au/…

    Uluṟu, also known as Ayers Rock, is a large sandstone rock formation in the southern part of the Northern Territory, central Australia. It lies 335 km (208 mi) south west of the nearest large town, Alice Springs; 450 km (280 mi) by road. Kata Tjuṯa and Uluṟu are the two major features of the Uluṟu - Kata Tjuṯa National Park. Uluṟu is sacred to the Pitjantjatjara and Yankunytjatjara, the Aboriginal people of the area. It has many springs, waterholes, rock caves and ancient paintings. Uluṟu is listed as a World Heritage Site.


    Name

    The local Pitjantjatjara people call the landmark Uluṟu (IPA: [uluɻu]). This word has no other meaning in Pitjantjatjara, but it is a local family name.[citation needed]

    In October 1872 the explorer Ernest Giles was the first non-indigenous person to sight the rock formation. He saw it from a considerable distance, and was prevented by Lake Amadeus from approaching closer. On 19 July 1873, the surveyor William Gosse visited the rock and named it Ayers Rock in honour of the then-Chief Secretary of South Australia, Sir Henry Ayers.[1] The Aboriginal name was first recorded by the Wills expedition in 1903.[citation needed] Since then, both names have been used, although Ayers Rock was the most common name used by outsiders until recently.

    In 1993, a dual naming policy was adopted that allowed official names that consist of both the traditional Aboriginal name and the English name. On 15 December 1993, it was renamed "Ayers Rock/Uluṟu" and became the first officially dual-named feature in the Northern Territory. The order of the dual names was officially reversed to "Uluṟu/Ayers Rock" on 6 November 2002 following a request from the Regional Tourism Association in Alice Springs.[citation needed]

    Description

    Uluṟu is one of Australia's most recognisable natural icons. The world-renowned sandstone formation stands 348 m (1,142 ft) high [863 m (2,831 ft) above sea level] with most of its bulk below the ground, and measures 9.4 km (5.8 mi) in circumference. Both Uluṟu and Kata Tjuṯa have great cultural significance for the Aṉangu Traditional landowners, who lead walking tours to inform visitors about the local flora and fauna, bush foods and the Aboriginal dreamtime stories of the area.

    Uluṟu is notable for appearing to change colour as the different light strikes it at different times of the day and year, with sunset a particularly remarkable sight when it briefly glows red. Although rainfall is uncommon in this semiarid area, during wet periods the rock acquires a silvery-grey colour, with streaks of black algae forming on the areas that serve as channels for water flow.

    Kata Tjuṯa, also called Mount Olga or The Olgas owing to its peculiar formation, is another rock formation about 25 km (16 mi) from Uluṟu. Special viewing areas with road access and parking have been constructed to give tourists the best views of both sites at dawn and dusk.

    Uluṟu panorama nearing sunset.

    Geology

    Uluṟu is an inselberg, literally "island mountain", an isolated remnant left after the slow erosion of an original mountain range.[2] Uluṟu is also often referred to as a monolith, although this is a somewhat ambiguous term because of its multiple meanings, and thus a word generally avoided by geologists. The remarkable feature of Uluṟu is its homogeneity and lack of jointing and parting at bedding surfaces, leading to the lack of development of scree slopes and soil. These characteristics led to its survival, while the surrounding rocks were eroded.[3] For the purpose of mapping and describing the geological history of the area, geologists refer to the rock strata making up Uluṟu as the Mutitjulu Arkose, and it is one of many sedimentary formations filling the Amadeus Basin.[2]

    Composition

    Uluṟu rock formations.
    Uluṟu rock formations.

    Uluṟu is dominantly composed of coarse grained arkose, a type of sandstone characterized by an abundance of feldspar, and some conglomerate.[4][2] Average composition is 50% feldspar, 25–35% quartz and up to 25% rock fragments; most feldspar is K-feldspar with only minor plagioclase as subrounded grains and highly altered inclusions within K-feldspar.[2] The grains are typically 2–4 mm in diameter, and are angular to subangular; the finer sandstone is well sorted, with sorting decreasing with increasing grain size.[2] The rock fragments include subrounded basalt, invariably replaced to various degrees by chlorite and epidote.[2] The minerals present suggest derivation from a predominantly granite source, similar to the Musgrave Block exposed to the south.[3] When relatively fresh, the rock has a grey colour, but weathering of iron-bearing minerals by the process of oxidation gives the outer surface layer of rock a red-brown rusty colour.[2] Features related to deposition of the sediment include cross-bedding and ripples, analysis of which indicated deposition from broad shallow high energy fluvial channels and sheet flooding, typical of alluvial fans.[2][3]

    Age and origin

    The Mutitjulu Arkose is believed to be of about the same age as the conglomerate at Kata Tjuṯa, and to have a similar origin despite the rock type being different, but it is younger and unrelated to the rocks exposed to the east at Mount Connor.[2] The strata at Uluṟu are nearly vertical, dipping to the south west at 85°, and have an exposed thickness of at least 2,400 m (7,900 ft). The strata dip below the surrounding plain and no doubt extend well beyond Uluṟu in the subsurface, but the extent is not known. The rock was originally sand, deposited as part of an extensive alluvial fan that extended out from the ancestors of the Musgrave, Mann and Petermann Ranges to the south and west, but separate from a nearby fan that deposited the sand, pebbles and cobbles that now make up Kata Tjuṯa.[2][3] The similar mineral composition of the Mutitjulu Arkose and the granite ranges to the south is now explained. The ancestors of the ranges to the south were once much larger than the eroded remnants we see today. They were thrust up during a mountain building episode referred to as the Petermann Orogeny that took place in late Neoproterozoic to early Cambrian times (550-530 Ma), and thus the Mutitjulu Arkose is believed to have been deposited at about the same time. The arkose sandstone which makes up the formation is comprised of grains that show little sorting based on grain size, exhibit very little rounding and the feldspars in the rock are relatively fresh in appearance. This lack of sorting and grain rounding is typical of arkosic sandstones and is indicative of relatively rapid erosion from the granites of the growing mountains to the south. The layers of sand were nearly horizontal when deposited, but were later tilted to their near vertical position during a later episode of mountain building, possibly the Alice Springs Orogeny of Palaeozoic age (400-300 Ma).[2]

    Fauna and flora

    Black-flanked Rock-wallaby (Petrogale lateralis).
    Black-flanked Rock-wallaby (Petrogale lateralis).

    Historically, 46 species of native mammals are known to have been living in the Uluṟu region; according to recent surveys there are currently 21. Aṉangu acknowledge that a decrease in the number has implications for the condition and health of the landscape. Moves are supported for the reintroduction of locally extinct animals such as Malleefowl, Common Brushtail Possum, Rufous Hare-wallaby or Mala, Bilby, Burrowing Bettong and the Black-flanked Rock-wallaby.[5]

    The Mulgara, the only mammal listed as vulnerable, is mostly restricted to the transitional sand plain area, a narrow band of country that stretches from the vicinity of Uluṟu to the Northern boundary of the park and into Ayers Rock Resort. This area also contains the marsupial mole, Woma Python or kuniya, and Great Desert Skink.

    The bat population of the park comprises at least seven species that depend on day roosting sites within caves and crevices of Uluṟu and Kata Tjuṯa. Most of the bats forage for aerial prey within 100 m (330 ft) or so from the rock face. The park has a very rich reptile fauna of high conservation significance with 73 species having been reliably recorded. Four species of frog are abundant at the base of Uluṟu and Kata Tjuṯa following summer rains. The Great Desert Skink is listed as vulnerable.

    Aṉangu continue to hunt and gather animal species in remote areas of the park and on angu land elsewhere. Hunting is largely confined to the Red Kangaroo, Australian Bustard, Emu and lizards such as the Sand Goanna and Perentie.

    Of the 27 mammal species found in the park, six are introduced: the house mouse, camel, fox, cat, dog and rabbit. These species are distributed throughout the park but their densities are greatest in the rich water run-off areas of Uluṟu and Kata Tjuṯa.

    Trees at the base of Uluṟu.
    Trees at the base of Uluṟu.

    Uluṟu - Kata Tjuṯa National Park flora represents a large portion of plants found in Central Australia. A number of these species are considered rare and restricted in the park or the immediate region. There are many rare and endemic plants at Uluṟu and Kata Tjuṯa.

    The growth and reproduction of plant communities rely on irregular rainfall. Some plants are able to survive fire and some are dependent on it to reproduce. Plants are an important part of Tjukurpa, and there are ceremonies for each of the major plant foods. Many plants are associated with ancestral beings.

    Flora in Uluṟu - Kata Tjuṯa National Park can be broken into the following categories:

    Trees such as the Mulga and Centralian Bloodwood are used to make tools such as spearheads, boomerangs and bowls. The red sap of the bloodwood is used as a disinfectant and an inhalant for coughs and colds.

    There are several rare and endangered species in the park. Most of them, like Adder's Tongue ferns, are restricted to the moist areas at the base of the formation, which are areas of high visitor use and subject to erosion.

    Since the first Europeans arrived, 34 exotic plant species have been recorded in the park, representing about 6.4% of the total park flora. Some, such as perennial buffel grass (Cenchrus ciliaris), were introduced to rehabilitate areas damaged by erosion. It is the most threatening weed in the park and has spread to invade water- and nutrient-rich drainage lines. A few others, such as burrgrass, were brought in accidentally, carried on cars and people.

    Climate and seasons

    Bush tucker from the area of Alice Springs Desert Park.
    Bush tucker from the area of Alice Springs Desert Park.

    The park receives an average rainfall of 307.7 mm (12.1 in) per year, and average temperatures are 37.8 °C (100.0 °F) in the summer and 4.7 °C (40.5 °F) in the winter. Temperature extremes in the park have been recorded at 45 °C (113 °F) during the summer and −5 °C (23 °F) during winter nights. UV levels are extreme most days, averaging between 11 and 15.[6]

    Local Aboriginal people recognise five seasons:

    1. Piriyakutu (August/September) - Animals breed and food plants flower
    2. Mai Wiyaringkupai (November/December) - The hot season when food becomes scarce
    3. Itjanu (January/February/March) - Sporadic storms can roll in suddenly
    4. Wanitjunkupai (April/May) - Cooler weather
    5. Wari (June/July) - Cold season bringing morning frosts

    History

    Satellite photo of Uluṟu.
    Satellite photo of Uluṟu.

    Archaeological findings to the east and west indicate that humans settled in the area more than 10,000 years ago.[7] Europeans arrived in the Australian Western Desert in the 1870s. Uluṟu and Kata Tjuṯa were first mapped by Europeans in 1872 during the expeditionary period made possible by the construction of the Australian Overland Telegraph Line. In separate expeditions, Ernest Giles and William Gosse were the first European explorers to this area.

    While exploring the area in 1872, Giles sighted Kata Tjuṯa from a location near Kings Canyon and called it Mount Olga, while the following year Gosse observed Uluṟu and named it Ayers Rock. Further explorations followed with the aim of establishing the possibilities of the area for pastoralism. In the late 1800s, pastoralists attempted to establish themselves in areas adjoining the South western/Petermann Reserve and interaction between Aṉangu and white people became more frequent and more violent. Due to the effects of grazing and drought, bush food stores became depleted. Competition for these resources created conflict between the two groups, resulting in more frequent police patrols. Later, during the depression in the 1930s, Aṉangu became involved in dingo scalping with 'doggers' who introduced Aṉangu to European foods and ways.

    Between 1918 and 1921, large adjoining areas of South Australia, Western Australia and Northern Territory were declared as Aboriginal reserves, sanctuaries for nomadic people who had virtually no contact with European settlers. In 1920, part of Uluṟu - Kata Tjuṯa National Park was declared an Aboriginal Reserve (commonly known as the South-Western or Petermann Reserve) by the Australian government under the Aboriginals Ordinance.

    Helicopter photo of Uluṟu.
    Helicopter photo of Uluṟu.

    The first tourists visited the Uluṟu area in 1936. From the 1940s, the two main reasons for permanent and substantial European settlement in the area were Aboriginal welfare policy and the promotion of tourism at Uluṟu. In 1948, the first vehicular track to Uluṟu was constructed, responding to increased tourism interest in the region. Tour bus services began in the early 1950s, and in 1958, the area that is now the Uluṟu - Kata Tjuṯa National Park was excised from the Petermann Reserve to be managed by the Northern Territory Reserves Board as the Ayers Rock - Mt Olga National Park, thus more fully opening the region to tourism.

    The first ranger was the legendary central Australian figure Bill Harney. By 1959, the first motel leases had been granted and Eddie Connellan had constructed an airstrip close to the northern side of Uluṟu.[1]

    On 26 October 1985, the Australian government returned ownership of Uluṟu to the local Pitjantjatjara Aborigines, with one of the conditions being that the Aṉangu would lease it back to the National Parks and Wildlife agency for 99 years and that it would be jointly managed. The Aboriginal community of Mutitjulu, population of approximately 300, is located near the western end of Uluṟu. From Uluṟu it is 17 km (11 mi) by road to the tourist town of Yulara, population 3,000, which is situated just outside of the national park.

    Legends and superstitions

    A variety of Aboriginal legends account for the existence of Uluṟu and its many cracks and fissures. One tells of serpent beings who waged many wars around Uluṟu, scarring the rock. Another myth recounts that two tribes of ancestral spirits were invited to a feast, but were distracted by the beautiful Sleepy Lizard Women and did not show up. In response, the angry hosts sang evil into a mud sculpture that came to life as the dingo. There followed a great battle, which ended in the deaths of the leaders of both tribes. The earth itself rose up in grief at the bloodshed, becoming Uluṟu.[8]

    It is often reported that those who take rocks from the formation will be cursed and suffer misfortune. There have been many instances where people who removed such rocks attempted to mail them back to various agencies in an attempt to remove the perceived curse.[9]


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    GEOLOGICAL MONOLITHS

    http://en.wikipedia.org/wiki/Monoliths

    Monolith

    From Wikipedia, the free encyclopedia

    A monolith is a geological feature such as a mountain, consisting of a single massive stone or rock, or a single piece of rock placed as, or within, a monument. Erosion usually exposes the geological formations, which are most often made of very hard and solid metamorphic or sedimentary rock.

    The word derives from the Latin word monolithus from the Greek word μονόλιϑος (monolithos), derived from μόνος ("one" or "single") and λίϑος ("stone").

    Mount Augustus is often claimed to be the largest monolith on Earth
    Mount Augustus is often claimed to be the largest monolith on Earth

    Geological monoliths

    The three largest on Earth are:

    1. Mount Augustus, in Western Australia - 860m
    2. La Peña de Bernal, in Mexico
    3. Stone Mountain, in Stone Mountain Park, Stone Mountain, a suburb of Atlanta, Georgia, USA

    Others include:

    North America

    Europe

    Africa

    Asia

    Australia

    South America

    Antarctica

    Many of these have legends attached.

    Labels:


    Tuesday, November 13, 2007

     

    Yellowstone Magma Chamber

    Yellowstone Volcano Rises at Unprecedented Rate

    By Andrea Thompson, LiveScience Staff Writer

    posted: 08 November 2007 02:00 pm ET


    Yellowstone’s ancient volcanic floor has been rising since mid-2004 because a blob of molten rock the size of Los Angeles infiltrated the system 6 miles beneath the surface, scientists say, but there is no risk of an eruption.

    Yellowstone National Park is the site of North America's largest volcanic field, which is produced by a hotspot, or gigantic plume of hot, molten rock, that begins at least 400 miles (643 kilometers) beneath Earth's surface and rises to 30 miles (48 kilometers) underground, where it widens to about 300 miles across.

    Occasionally, blobs of magma break away from the top of this plume and rise up to resupply the magma chamber beneath the park's "caldera," a 40-mile by 25-mile bowl-like depression and volcanic leftover whose walls you can see in the northwest part of the park.

    These rising blobs of magma can sometimes push on the caldera floor, causing it to rise. Scientists monitoring the Yellowstone caldera think that's exactly what has caused the caldera floor to rise by almost 3 inches (7 centimeters) per year over the past three years—more than three times faster than it has more typically risen since observations began in 1923.

    "Our best evidence is that the crustal magma chamber is filling with molten rock," said study leader Robert Smith, a seismologist at the University of Utah. "But we have no idea how long this process goes on before there either is an eruption or the inflow of molten rock stops and the caldera deflates again."

    Smith and his colleagues, whose work is detailed in the Nov. 9 issue of the journal Science, say that there is no indication that the caldera will produce an eruption anytime soon.

    "There is no evidence of an imminent volcanic eruption or hydrothermal explosion. That's the bottom line," Smith said. "A lot of calderas worldwide go up and down over decades without erupting."

    Other well known calderas include California's Long Valley and Italy's Campi Flegrei, near Naples, which have both been known to rise and subside again for even tens of thousands of years without erupting.

    The recent uplift of the Yellowstone caldera, recorded by GPS and satellite radar measurements, is considerably faster than the previous record of 0.8 inches (2 centimeters) per year from 1976 to 1985.

    Smith and his teams used computer simulations to determine changes in the shape of the magma chamber, which acts as a sponge-like body that holds magma between areas of solid rock. They found that the magma pushing up on the caldera is likely about 38 miles long and 13 miles wide, about the area of the city of Los Angeles, but only tens to hundreds of yards thick.

    The magma that accumulates in the chamber powers Yellowstone's famous geysers and hot springs, the largest hydrothermal field in the world.

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    http://en.wikipedia.org/wiki/Yellowstone_Caldera



    Yellowstone Caldera

    From Wikipedia, the free encyclopedia

    Yellowstone Caldera

    The northeastern part of Yellowstone Caldera, with the Yellowstone River flowing through Hayden Valley and the caldera rim in the distance
    Elevation 10,308 feet (3,142 m) at Mount Sheridan
    Location Wyoming, U.S.
    Range Rocky Mountains
    Coordinates 44°24′N, 110°42′W
    Topo map USGS Yellowstone National Park
    Type Caldera
    Age of rock 70,000 – 2.1 million years
    Last eruption 640,000 years ago
    Easiest route hike/auto/bus

    The Yellowstone Caldera is a volcanic caldera in Yellowstone National Park in the United States. It is located in the northwest corner of Wyoming, measuring about 55 kilometers (34 mi) by 72 kilometers (45 mi). The caldera was discovered based on geological field work conducted by Bob Christiansen of the United States Geological Survey in the 1960s and 1970s. After a BBC television science program coined the term supervolcano in 2000, it has often been referred to as the "Yellowstone supervolcano."


    [ Volcanism

    Yellowstone, like the Hawaiian Islands, is believed to lie on top of one of the planet's few dozen hot spots where light hot molten mantle rock rises towards the surface. The Yellowstone hot spot has a long history. Over the past 17 million years or so, successive eruptions have flooded lava over wide stretches of Washington, Oregon, California, Nevada, and Idaho, forming a string of comparatively flat calderas linked like beads, as the North American plate moves across the stationary hot spot. The oldest identified caldera remnant is straddling the border near McDermitt, Nevada-Oregon. The calderas' apparent motion to the east-northeast forms the Snake River Plain. However, what is actually happening is the result of the North American plate moving west-southwest over the stationary hot spot deep underneath.

    Yellowstone sits on top of three overlapping calderas. (USGS)
    Yellowstone sits on top of three overlapping calderas. (USGS)

    Currently, volcanic activity is exhibited only via numerous geothermal vents scattered throughout the region, including the famous Old Faithful Geyser, but within the past two million years, it has undergone three extremely large explosive eruptions, up to 2,500 times the size of the 1980 Mount St. Helens eruption. The three eruptions happened 2.1 million years ago, 1.3 million years ago, and the most recent such eruption produced the Lava Creek Tuff 640,000 years ago and spread a layer of volcanic ash over most of the North American continent. Smaller steam explosions occur every 20,000 years or so; an explosion 13,000 years ago left a 5 kilometer diameter crater at Mary Bay on the edge of Yellowstone Lake (located in the center of the caldera). Additionally, non-explosive eruptions of lava flows have occurred in and near the caldera since the last major eruption; the most recent of these was about 70,000 years ago. Craters of the Moon National Monument in Idaho is the result of volcanic activity between 11,000 and 2,000 years ago.

    The volcanic eruptions, as well as the continuing geothermal activity, are a result of a large chamber of magma located below the caldera's surface. The magma in this chamber contains gases that are kept dissolved only 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 gases bubble out and cause the magma to expand. This can cause a runaway reaction. If the expansion results in further relief of pressure, for example, by blowing crust material off the top of the chamber, the result is a very large gas explosion.

    [ Volcanic hazard

    A full-scale eruption of the Yellowstone caldera could result in millions of deaths locally and catastrophic climatic effects globally, but there is little indication that such an eruption is imminent. [1] However, the system is not yet completely understood, and the study of Yellowstone is ongoing. Geologists are closely monitoring the rise and fall of the Yellowstone Plateau, which averages +/- 1.5 cm yearly, as an indication of changes in magma chamber pressure.[1][2] Major eruptions of the Yellowstone hotspot appear to occur roughly every 700,000 years. The Lava Creek Tuff eruption 630,000 years ago was last major eruption.

    [ Origin

    Location of Yellowstone Hot Spot in Millions of Years Ago
    Location of Yellowstone Hot Spot in Millions of Years Ago

    The source of the Yellowstone Hot Spot is not without controversy. Some geoscientists theorize that the Yellowstone Hot Spot is the effect of an interaction between local conditions in the lithosphere and upper mantle convection (G.R. Foulger: [2] and [3]). Others prefer a deep mantle origin (mantle plume). (See list of off-line references in mantleplumes.org/CRB.html). No theory is close to airtight. Part of the controversy is due to the rather sudden appearance of the hot spot in the geologic record. Additionally, the Columbia Basalt flows appear at the same approximate point in time, causing speculation about their origin.[4]

    [ See also

    [ Further reading


    [ External links

    Retrieved from "http://en.wikipedia.org/wiki/Yellowstone_Caldera"

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    http://www.angelfire.com/punks4/jbizzle

    Sleeping Giant: The Yellowstone Caldera Super Volcano

    By: Justin Reynolds

    Yellowstone National Park is our nation’s oldest, most recognized recreational areas due to its many geysers, thermal pools, mountain views, and a vast array of wildlife, including most of America’s remaining herds of bison. As a result of its popularity, the park attracts nearly 3 million visitors yearly, (www.nps.gov/yell). Yet, what many of these visitors do not realize is that landmarks they came to visit, such as Old Faithful and the park’s other numerous geysers, are fueled by a sleeping giant. Underneath Yellowstone there rests one of the world’s largest, potentially harmful volcanoes known to man, and if historical records prove true, it is due to blow.

    http://volcanoes.usgs.gov/yvo/figures/fig1.html

    The question for geologists is what fuels this volcano and the various geothermal features dotted across Yellowstone? Geologists refer to the phenomenon as the Yellowstone Hot Spot (Francis 197). A hot spot is a location in the Earth’s crust where magma flows up from the magma, forming volcanoes in its wake. The hotspot has been affecting the area for the last 16 million years, yet scientific understanding of its effect on Yellowstone’s formation has only just begun. What is known is that the hotspot is relatively stationary within the depths of Earth, and the North American tectonic plate is moving in a southwest direction over the hotspot at a rate of 4.6 centimeters annually, (Direction). While the North American plate moved southwest over the hotspot, the volcanic formations progressed northeast, beginning in northern Nevada and southeast Oregon 16.5 million years ago and reaching its present day location near Yellowstone National Park 2 million years ago, (Direction). The current location of the Yellowstone hotspot is shown in the figure to the right. The orange outlines are the outlines of the three calderas which have resulted from eruptions during the past 2 million years. Notice how mountains have formed a parabolic shape around the hotspot as the North American plate moves southwest over the hotspot.

    Volumes of Yellowstone's largest eruptions compared to large historic eruptions.

    http://volcanoes.usgs.gov/yvo/figures/fig2.html

    Map showing the area of the US that was once covered by ash from Yellowstone eruptions.

    http://volcanoes.usgs.gov/yvo/figures/fig3.html

    During the past 2 million years, the volcanic region has been subject to 3 definable cycles of activity, all occurring approximately 600,000 years apart, (Fisher 107). The first occurred about 2 million years ago and produced a massive 2,500 cubic kilometers of volcanic ash. The next happened 1.2 million years ago, resulting in 280 cubic kilometers. The most recent took place 600,000 years ago, resulting in 1,000 cubic kilometers of ash, (Fisher 108). In comparison, the eruption of Mt. St. Helens in 1980 created an enormous amount of destruction while only spewing 2.5 cubic kilometers of erupted ash, (Fisher 108). The diagram to the left shows the immense amount of ash associated with the three eruptions compared to some other notable volcanic eruptions. The first Yellowstone eruption produced 1,000 times the ash alone! To the right is a diagram showing the ash distribution across America as a result of the Yellowstone eruptions compared to the Mt. St. Helens eruption. As the diagram shows, an eruption of such large scale would surely be devastating to the Great Plains and Western states. The eruption which occurred 2 Million years ago provided enough ash to cover or partially cover 20 states. In contrast the St. Helens volcano only partially covered a few regionalized states in 1980.

    The substances present in the magma chamber underneath Yellowstone prior to eruption were composed of ryholite lava and volcanic ash. Ryholite lava is very viscous, meaning that it is very thick and flows slowly due to friction, (Francis 141). It is the opposite of Basalt lava which is less viscous and flows freely. In each case, pressure built up to insurmountable levels due to the thick nature of the ryholite lava present, which led to three of Earth’s largest known pyroclastic-flow eruptions. The eruptions, mentioned previously, were powerful enough to result in a massive blanket of volcanic ash that was deposited as far east as Louisiana, (Ash).

    In the wake of these eruptions, three separate calderas were formed in relation to their eruption, as the top of the magma chamber producing the ryholite lava collapsed due to the lack of structural support provided by the lava. A caldera is a large, more-or-less circular depression surrounded by steep cliffs, and formed when a magma chamber empties out its magma, and the surface above the chamber collapses. (Francis 292). The Yellowstone Caldera is presently 45 km in diameter and 75 km in length. However, it will ultimately take a new form when the next massive eruption occurs.

    Map showing the locations of features in the photogallery.

    http://volcanoes.usgs.gov/yvo/gallery_map.html

    Recently in April of 2004, over 500 earthquakes were recorded in the general Yellowstone region. The largest was just below 3.0 in magnitude, not incredibly large, yet the sheer numbers are somewhat disturbing. At one point, according to seismic recording stations near Yellowstone, over an eleven day period, 465 individual earthquakes were recorded near or at the caldera. In addition, a “bulge” has recently been recorded in the center of the caldera. A recorded rise of 86 centimeters was observed between 1923 and 1984, and then it subsided slightly between 1985 and 1989 until rising again recently, (Fisher 109). The significance of these fluctuations is unknown, but it is believed to be related to the level of the magma present in the underground chambers beneath Yellowstone.

    Could the “bulge” be a sign of future volcanic activity? Scientists are unsure, as there is currently no technology present that is capable of predicting earthquakes. The activity of Yellowstone’s hydrothermal system does not vary much from other similar large calderas, yet historical records of volcanic activity in the region suggest that a potentially cataclysmic eruption should occur in the near future, (Fisher 111). Each of the eruptions that occurred in the past, were spaced about 600,000 years apart, the same amount of time between the last eruption and now.

    Diagram physical and chemical processes of volcanic gas interactions in atmosphere

    http://volcanoes.usgs.gov/Hazards/What/VolGas/SO2Aerosols.html

    When dealing with volcanoes, potential eruptions are always a concern to scientists. What would another eruption of the Yellowstone Caldera mean to the rest of the World? As with previous eruptions, the ash expelled into the stratosphere, would blanket the entire Great Plains. Earth’s most fertile lands would be virtually blanketed in a layer of ash. Crops would fail, and a local and global shortage of grains would develop. The ash would work its way into the Mississippi-Missouri River system, polluting the water and filling in channels from North Dakota to the Gulf of Mexico, (Ash). This ash would also block out the sun light and result in an overall global cooling of a few degrees as shown in more depth above. Essentially, the effects of another eruption of the Yellowstone Caldera would be devastating to our planet and would surely test the resilience of mankind. Yet, by all scientific accounts, the activity that is occurring presently beneath our nation’s oldest national park does not pose an imminent threat towards mankind. But the possibility still remains of a catastrophic eruption in the near future unlike any man has ever seen.

    For more information on current seismic activity in the Yellowstone region see…

    Current Activity: http://volcanoes.usgs.gov/yvo/monitoring.html

    For more information on Yellowstone National Park visit…

    www.nps.gov/yell

    http://volcanoes.usgs.gov/yvo/images/2000-rbs-3.3yellashvolumes_large.jpg


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