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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, March 18, 2008

     

    monument valley sites/urls

    Photobucket
    http://www.americansouthwest.net/utah/photographs.shtml

    http://www.nps.gov/history/history/online_books/geology/publications/bul/1508/sec12c.htm
    click on previous/ next buttons for more views and info.

    http://www.utahmountainbiking.com/goodies/geology/moab.htm
    geological history of moon valley

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    Monday, March 17, 2008

     

    Ways to Cause Mass Extinctions

    http://palaeo.gly.bris.ac.uk/Palaeofiles/Triassic/triextict.htm

    Theories on the Triassic-Jurassic Extinction


    Picture from www.und.nodak/volcanoes.

    Fluctuating Sea-level change.

    The Earth got hit by a large rock

    There was no extinction

    Death by Volcano

    Climate Change

    Why do we think there was a 'mass' extinction?

    Return to the Homepage Go to. How to cause a mass extinction

    Go to Ecology of the Triassic

    Go to Evidence of Extinction

    ...................................

    http://palaeo.gly.bris.ac.uk/Palaeofiles/Triassic/extinction.htm

    WHAT IS AN EXTINCTION?

    Extinction is the process in which groups of organisms die out. If over an extended period of time the birth rate of a species is less than the death rate, then extinction will eventually occur.

    Extinction is a natural phenomenon predicted by Darwin in his theory of evolution. A species goes extinct if it is not able to adapt to changes in it's environment, or compete effectively with other organisms.

    Over the history of the earth over 99% of all the species that have ever lived have gone extinct.

    WHAT IS A MASS EXTINCTION?

    Mass extinctions are periodic rises in the extinction rate above the background level. They are events which are not caused by changes in habitat or competition but catastrophes.

    Perhaps over 95% of all extinctions have occurred as background events, with the rest consisting of catastrophic events which:-

    These are the mass extinctions, they cause a dramatic decrease in the earth's biodiversity, and punctuate the earth's history, and are used by Geologists to break up geological time. Recent thinking has however been to class events by their ecological impacts, rather than by the number of species lost. Click HERE for a brief summary on this topic.

    Five main extinction events have been recognized, these are known as the BIG 5.

    1. The late Ordovician event 438 million years ago, when 100 families went extinct
    2. Late Devonian 360 million years ago, when 30% of families went extinct
    3. End Permian 245 million years ago, the biggest extinction of all time when over 50% of all families were lost.
    4. Late Triassic 35% of families died out
    5. The Cretaceous Tertiary (K-T) 65 Million years ago, which ended the reign of the dinosaurs

    SEE TIMELINE



    .........................................
    http://palaeo.gly.bris.ac.uk/Palaeofiles/Triassic/exttheory.htm

    WAYS TO DESTROY LIFE

    Of all the ways in which scientists have proposed that it is possible to cause a mass extinction here are a few of the front runners. Conceptually there are 4 main ways in which the earth has tried to wipe out life on our planet.

    1. Freeze it (Snowball Earth)
    2. Boil it (Greenhouse Earth)
    3. Drop a meteor on it ( Meteor Impact)
    4. Cover it with ash and Lava ( Giant Volcanic Eruption)

    Now that's all very well and good but, how do these physical effects cause mass extinctions?

    It is important to realise that numbers 3 and 4 are essentially ways which have been put forward to explain 1 and 2, though Snowball earth and Greenhouse earth are still theories in their own right, as they are to some extent self replicating, i.e. we rather get stuck in vicious circles as the more we warm the earth, the more greenhouse gasses we can potentially release, (at least in theory).

    1. Snowball Earth

    As we know today the addition of Carbon dioxide into the atmosphere, stops ultra violet rays that impact into the earth from leaving again, by trapping them in the same way as a greenhouse does. Carbon dioxide is not the only gas that stops the escape of UV radiation, Methane is much more efficient. So in the same way as the addition of these gasses to the atmosphere causes warming, so the removal of these gasses from the atmosphere would plunge the earth into 'snowball' conditions.

    Carbon dioxide is removed from the atmosphere all the time by plants during the process of photosynthesis, but a far more efficient removal process is needed to plunge the earth into icehouse conditions.

    Another common cause of cooling is ice ages, thought to be caused to be caused by astronomical forcing, related to the earths orbit.

    A snowball earth type mechanism is currently blamed for the End Ordovician extinction.

    For related information also see

    BBC Horizon Snowball earth

    Back to top

    2. Greenhouse Earth

    To create greenhouse conditions you need a rapid release of greenhouse gasses into the atmosphere so rapid that the feedback mechanisms ( i.e. plants and rocks) cannot compensate quick enough.

    Methane clathrates (otherwise known as Methane Hydrates) build up in permafrost, and in seafloor sediments, through the action of Methanogen bacteria buried in organic sediment. Methane clathrates are metastable, (i.e. unstable in most conditions) and can easily be released by climatic change, a change in sea level or earthquakes. Any one of these events would release huge amounts of methane into the atmosphere, so potentially starting the cycle of global warming.

    Carbon dioxide levels are controlled to some extent in the earth system by feedback mechanisms including photosynthesis and carbonate deposition. The largest reservoir of Carbon Dioxide is in the Oceans, the best way to generate a huge release of carbon dioxide would be to keep the two reservoirs of the atmosphere and the ocean separate, then stop ocean circulation. This would in effect create a loaded gun, which would be unloaded when circulation returned to the ocean.

    Pnatholossa the giant world ocean may well have stopped circulating after the late Palaeozioic glaciations, the lack of ice at the poles would have meant there was no influx of cold water to drive the oceanic heat engine, and since there where no isolated basin seas there was no hypersaline water to drive a saline circulation belt. All that needed to occur then was overturn of water to release huge volumes of carbon dioxide, which may have triggered the End Permian extinction.

    Back to top

    3. Drop a rock on it

    In many of the mass extinctions known on earth there is evidence of meteor impact, from some location in the world, in the case of the Cretaceous- Tertiary event, there is the Chicxulub crater of the coast of New Mexico, which is widely stated as at very least a contributing factor to the events.

    meteor1.jpg (27638 bytes) Picture taken from

    www.earthchangestv.com

    The theory of extinctions caused by extraterrestrial bodies was first popularised by Louis Alverez, in his work on the K-T (Cretaceous Tertiary event). The ideas have been expanded by many scientists. An example of this is the Nemesis Hypothesis, put forward by Raup and Sepkoski.

    The Nemesis Hypothesis

    The theory as based around the observations of Raup and Sepkoski on the incidence of marine extinctions through time. They proposed that the extinctions observed on the earth had a cyclicity of 26Ma. This paper was read by Dr Richard Miller of the University of California, who was the first to link the cyclicity to a astronomical event. The theory goes that a brown giant star circles our sun somewhere between Pluto and the nearest star Proxima Centauri. When this brown giant passes the sun it disturbs the Oort cloud, which lies beyond the reaches of Pluto, causing comet showers in the interior of the solar system. There are however a number of problems with this theory, not least that the Nemesis planet has not yet been discovered though supporters of the theory would be quick to point out that a brown giant star emits little or no light, so would be rather hard to find. Other problems are that in the vastness of space the chances of a comet disturbed from the Oort cloud consistently hitting the earth are rather slim, (probably somewhere less than your chances of winning the lottery) though if a large number of comets were pulled form the Oort cloud, the chances would increase.

    It Must be stressed that the Nemesis Hypothesis, is just that a hypothesis, devised as a possible explanation for the cyclicity in extinctions discovered by Raup and Sepkoski. There is however doubt even in the cyclicity as many Palaentoloigists argue that the dates quoted in the study are flawed. The theory does however present an interesting point that mass extinctions may not be as random and unpredictable as it first seems.

    In the End Triassic extinction event, at least 2 craters have been found of about the right age, the first is in Western Australia, where scientists have discovered a 75 mile (120km) wide crater. Another has been found in Quebec Canada, surrounding the Manicouagan Reservoir, with an age of 210 million years old. Which seems to add weight to the theory that mass extinctions may well also be in some way assisted by impacts.

    One of the questions associated with meteor impacts is how could it cause a mass extinction. Obviously several hundred tons of rock, hurtling towards you faster than sound is bad news if you happen to be stood underneath it, but if the impact were large enough, if would be equally bad news if you were on the other side of the earth. Molten fragments of rock would rain down for hundreds of miles around, starting forest fires, which would belch carbon dioxide and smoke in to the atmosphere. One of the first effects of an impact globally would be earthquakes which would lead to huge tsunamis or tidal waves all around the globe, destroying coastlines. For those organisms which had survived the first few months of this an even worse fate would be instore, the ash and dust which had been ejected into the atmosphere by the impact and the fires, would eventually shroud the globe plunging the earth into perpetual night. This night would last for years and would cause a crash in the ecosystems on both land and sea. The first to suffer would be those reliant on sunlight like the plants, in turn the herbivores would suffer and eventually the carnivores. Until all levels of the food chain would be affected, even the scavengers and parasites (because after all even fleas need to live somewhere), causing the extinctions of many groups of animals, and plants.

    For more information please see

    The K-T Impact

    Asteroid Impacts

    Back to top

    4. Cover it with ash and lava (Volcanic Eruption)

    It doesn't take a lot of imagination to realize that being covered in molten rock, at temperatures in excess of 400oc would be rather bad news. However you need a bit more imagination to understand to terrors of huge volcanic eruptions. Over larger areas it is the gasses, and ash that do the killing, after all one eruption could not generate enough lava to cover the whole world and lavas only spread a short distance.

    deep hawaii lavaflow.jpg (5855 bytes)

    Click on the Image for an enlargement

    Picture from deep hawaii.com

    Recent work around Yellowstone National park in the USA, discovered the preserved remains of a whole herd of Rhinos. When the remains were examined by forensic scientists an unusual cause of death was discovered. The rhinos had essentially drowned in their own bodily fluids, but how? It turns out that Yellowstone National Park is essentially the 'crater' of a huge volcano. In volcanic eruptions huge amounts of ash are erupted into the atmosphere much if this is tiny shards of volcanic glass. The Rhinos had breathed these shards of glass, which had lodged in their lungs, puncturing and cutting the skin and leading to internal bleeding.. Even today we are well aware of the devastating effects of ash, when it comes in the form of Pyroclastic flows, which sweep rapidly down mountains, like a boiling avalanche, yet even these effects of ash are local and could not cause a worldwide extinction event like the one we see at the end of the Triassic.

    From studies of volcanic eruptions today we know that huge volumes of gas are erupted into the atmosphere. We know a large part of this is Carbon Dioxide, which as we have already seen is a greenhouse gas, other gasses include Sulphur Dioxide, which today is a major cause of acid rain, and it's associated effects. There is also a large amount of dust and ash ejected into the upper atmosphere, which helps to cause some of the beautiful sunsets we see, this however helps to scatter the light destined for the earths surface.

    To create a mass extinction we need to eject huge volumes of gas into the atmosphere, which requires huge scale volcanic eruptions most often associated with flood basalts, such as the Siberian, and Deccan Traps, which occurr when plumes of hot magma rise from the core, and break the earths surface. A likely cause of End Triassic vulcanism is the opening of the Atlantic Ocean.

    For More Information see.

    Super-Volcanoes

    Back to top

    But how do these physical events set off mass extinctions?

    The simplest answer to this is climate. Every species alive on earth today and so presumably in the past is adapted to a certain range of conditions. In the same way that if we were suddenly whisked off to the North Pole and expected to live there for a year with only a wooly jumper and a Mars bar, we would surely die. It is the same in an extinction event, climatic zones essentially shift around the globe (so us being placed on the north pole is not as far fetched as you first thought), or ecosystems are starved of light or nutrients. This results in plants and animals being out of equilibrium with their surroundings, this not only causes the death of individuals but whole species. With the death of a species so there is a gap in the food chain, and so even animals which have adapted to the new climate find themselves with no food so die out and so on (see box 1)

    BOX 1. EXTINCTION PROBLEMS IN A STRANGE ECOSYSTEM

    If we go back to our example of us sat at the North Pole, but this time with a whole box of Mars bars, assuming we did not freeze to death in the first day, we would slowly become more accustomed to the cold, maybe we would find shelter from the cold, but either way as soon as our prey (the Mars Bars) ran out, unless we found an alternative source of food we would starve. To create a more dynamic ecosystem let us assume we provide a food source for another organism such as a polar bear, now if we died what would the polar bear eat?

    Unfortunately my example falls down here as no one is going to believe that without us eating Mars bars they're going to reproduce uncontrollably. However, in our North Pole ecosystem of Mars bars, us and Polar bears, let us assume we find extra clothes and shelter, so the cold no longer controls our numbers, and we manage to find the recipe and ingredients for mars bars (and by some freak coincidence they provide us with all the essential nutrients for life), in this case it would be the polar bears controlling our numbers since they are our direct predators. So if polar bears were wiped out, then our numbers would no longer be controlled, so our population would over many generations grow, until eventually we could no longer supply ourselves with mars bars, or we may have even eaten all the mars bars in the world. This would cause a huge population crash, or maybe even extinction of the human race (or at least those dependant on Mars Bars). This rather abstract example helps illustrate the point that all the trophic levels of a food chain (or web) need to be in place, otherwise there will be instability in all other populations.

    It is really the change in the climate caused by the physical event, that causes the death of the organism (unless of course there were a very small population of a species and they all happened to be stood under a falling meteor). So the mechanisms we discussed on this page are really the means to an ends or the triggers if you like. These triggers don't have to be as dramatic for normal extinctions of course, maybe a plant species is replaced by a newer and better adapted plant, as happened when grasses took over from ferns. In this case maybe the herbivores which evolved to live on the previous plant species, couldn't live on the new species and so would go extinct. Leading to extinctions across the food web. This could possibly cause a mass extinction though we have no obvious examples in the record.

    Back to top

    Go To Ecology Of the Triassic

    Go to Theories on the Triassic mass extinctions

    Return to Homepage What is an Extinction? Ways to cause an extinction Go the the Glossary

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    She Pours Out Her Essence to Create land masses - Large Igneous Provinces

    Large igneous province

    From Wikipedia, the free encyclopedia

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

    Large Igneous provinces (LIPS) were originally defined by Coffin and Eldholm (1992) as areas of Earth's surface that contain very large volumes of magmatic rocks (typically basalt but including rhyolites) erupted over extremely short geological time intervals of a few million years or less. These provinces are not associated with normal plate tectonic magmatism, ie, mid-ocean ridges and island arcs. LIPS include continental flood basalts, oceanic plateaus, large dike swarms (the eroded roots of a volcanic province), and volcanic rifted margins, recognized by the presence of dike swarms and "seaward dipping reflectors" -- seismically-imaged tabular features buried deep beneath sediment that lie parallel to a passive continental margin along the continental slope, and interpreted to represent lava flows or sills that formed during rifting of the continent). Most LIPS consist of basalt, but some contain large volumes of associated rhyolite; the rhyolite is typically very dry compared to island arc rhyolites, with much higher eruption temperatures (850º to 1000º C) than normal rhyolites.

    When created, LIPS often occupy a few million km² and have volumes on the order of 1 million km3. In most cases, the majority of a LIP's volume is emplaced in less than 1 million years. One of the conundra of LIPS origins is to understand how enormous volumes of basaltic magma are formed and erupted over such short time scales, with effusion rates up to an order of magnitude greater than mid-ocean ridge basalts.


    Theories of formation

    Large igneous provinces are often linked to active hotspots by linear chains of volcanic islands or volcanoes, leading to models that connect their origins to mantle plumes. In this hypothesis, mantle plumes consist of a bulbous head and a thin tail that feeds hot mantle into the head. When the rising plume head encounters the lithosphere, it spreads out and melts catastrophically to form large volumes of basalt magma in 1-2 million years. Subsequent volcanism originates with the plume tail. The movement of lithosphere across the surface of the Earth in response to plate tectonics causes the plume tail volcanics to form linear island chains. The impact of the plume on the base of continental lithosphere may cause rifting and breakup of the continent, creating conjugate LIPS on opposite sides of an ocean basin (e.g., the Parana-Etendeka pair of South America-Africa).

    Alternate theories include delamination of eclogitic lower crust, edge effects of thick lithosphere, and meteorite impact (see Mantle plumes for more complete discussion of alternate models).

    Relationship to extinction events

    Because a LIP may in several cases have occurred simultaneously with oceanic anoxic events and extinction events, it has been proposed that the volcanic byproducts of LIP formation may have had a profound and deleterious effect on the global environment, perhaps contributing to extinction events. The most important examples are the Deccan Traps (Cretaceous–Tertiary extinction event), the Karoo-Ferrar (Pliensbachian-Toarcian extinction), the Central Atlantic Magmatic Province (Triassic-Jurassic extinction event), and the Siberian traps (Permian-Triassic extinction event).

    LIPS have two impacts on environment that can cause extinction: first, they release large volumes of sulfate gas that forms sulfuric acid in the atmosphere; this absorbs heat and causes substantial cooling (e.g., the Laki eruption in Iceland, 1783). Second, oceanic LIPS can reduce oxygen in seawater by either direct oxidation reactions with metals in hydrothermal fluids or by causing algal blooms that consume large amounts of oxygen (Kerr, 2005).

    Examples of LIPs

    These are well documented large igneous provinces in geological research.

    Continental Flood basalts

    Oceanic Plateaux

    Volcanic Rifted Margins

    Dike Swarms

    See also

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    CAMP - Central Atlantic Magmatic Province

    MAPPING THE CENTRAL ATLANTIC MAGMATIC PROVINCE
    J. Gregory McHone, GLSP, Wesleyan University, Middletown, CT 06459-0519

    Mesozoic basins that preserve extrusive basalts of the 200-Ma Central Atlantic Magmatic Province (CAMP) total about 300,000 km2. However, dikes and sills of CAMP that fed the basin basalts also occur across 11 million km2 within four continents, centered upon but extending far outside of the initial Pangaean rift zone. New maps show CAMP dikes, sills, and surface lavas, with evidence that the province includes regions between Texas and Venezuela along its western side. The N-S dimension of CAMP is greater than 5,000 km, with several dikes greater than 500 km long, sills exceeding 100,000 km3, and lava flows larger than 50,000 km2.

    In addition, basalts of the East Coast margin igneous province (ECMIP) of North America, which cause the East Coast Magnetic Anomaly, covered about 60,000 km2 with perhaps 1.3 million km3 of extrusive lavas. If only half of the continental CAMP area was originally covered by 200 m of lava, the total volume of CAMP and ECMIP extrusive basalt exceeded 2.4 million km3 and may be Earth's largest sub-aerial flood basalt event. A similar amount remains frozen in the uppermost crust.

    The distribution of chemical groups within the province is pertinent to geodynamic and petrologic models for the origin of this and other large flood basalt provinces. Radiometric and stratigraphic ages indicate most of the magmatic activity was everywhere brief and close to the Tr-J boundary, which is marked by a profound mass extinction. Huge emissions of CAMP volcanic gases would have caused major world-wide environmental problems. Proving a connection between CAMP volatiles and the mass extinction will depend on how precisely new radiometric dates for the basalts bracket the Tr-J boundary.
    Also see: http://jmchone.web.wesleyan.edu/CAMP.html
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    http://en.wikipedia.org/wiki/Central_Atlantic_Magmatic_Province

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    Central Atlantic Magmatic Province


    North Mountain basalt at Southwest Head, Grand Manan Island (Fundy basin)

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    Mass Extinctions- Causes?

    http://www.livescience.com/strangenews/070808_GM_mass_extinctions.html


    Greatest Mysteries: What Causes Mass Extinctions?

    By Charles Q. Choi, Special to LiveScience

    posted: 08 August 2007 09:28 am ET

    Editor's Note: We asked several scientists from various fields what they thought were the greatest mysteries today, and then we added a few that were on our minds, too. This article is one of 15 in LiveScience's "Greatest Mysteries" series running each weekday.

    They are known ominously as the Big Five—the five greatest mass extinctions over the past 500 million years, each of which is thought to have annihilated anywhere from 50 to 95 percent of all species on the planet.

    Many unsolved mysteries remain regarding these disasters, perhaps the greatest of which is what caused each of them. But research is uncovering how these extinction events dictated the fate of life on this planet—for instance, determining which animals first crawled onto land and which ruled the oceans.

    The main suspects behind these catastrophes seem to come either from above, in the form of deadly asteroids or comets, or from below, in the form of extraordinarily massive volcanism. Occasionally, however, unexpected culprits arise—for instance, otherwise innocuous forests.

    The K-T extinction

    The most recent of the Big Five is the most familiar one—the cataclysm that ended the Age of Dinosaurs. The end-Cretaceous or Cretaceous-Tertiary extinction event, otherwise known as K-T, killed off all dinosaurs save birds roughly 65 million years ago, as well as roughly half of all species on the planet, including pterosaurs.

    Not only did mammals sweep across the planet after K-T, but sharks expanded across the seas, explained American Museum of Natural History vertebrate paleontologist Jack Conrad.

    "Throughout the Age of Dinosaurs, you always had these large reptile carnivores dominating the water, such as ichthyosaurs, mosasaurs and plesiosaurs," Conrad explained. "Only after they die do you see big sharks becoming really prevalent. You probably wouldn't have seen orcas or blue whales either had reptile dominance of the seas not gone by the wayside."

    Although research suggests the planet was on the verge of environmental upheaval before the K-T extinction event, the straw that broke the dinosaur's back is widely thought to have been an impact with an asteroid or comet. Still, a number of researchers contend evidence commonly linked with such an impact, such as the metal iridium, which is rare on the Earth's crust, could also be caused by the massive volcanic eruptions at the Deccan Flats in India, another popular contender for the dinosaur-killing catastrophe.

    The Triassic-Jurassic extinction

    The end-Triassic, or Triassic-Jurassic extinction event about 200 million years ago is thought by many to possibly have set dinosaurs on the path to their 135-million-year domination of much of life on Earth. It also ended life for roughly half of all species.

    Until this disaster, mammal-like creatures known as therapsids were actually more numerous than the ancestors of the dinosaurs, known as archosaurs.

    "The dinosaurs definitely survived better than the early proto-mammals did, and the extinction event might have entirely tipped it in their favor," said Rutgers University paleobiologist George McGhee.

    Of the Big Five, the Triassic-Jurassic extinction has the fewest number of scientists currently researching it, "although that's changing right now," said Columbia University paleoecologist Paul Olsen. Its cause remains under great debate, with the best contender so far being the massive volcanic eruptions at the "Central Atlantic magmatic province," a region that encompassed a staggering 4.2 million square miles (11 million square kilometers), an area larger than Canada. Another main possibility could be an astronomical impact, Olsen said, although as with the K-T event, the evidence for both types of catastrophe can get maddeningly blurry.

    The Permian-Triassic extinction

    The largest of the Big Five was the end-Permian or Permian-Triassic extinction event roughly 250 million years ago, which eliminated as much as 95 percent of the planet's species.

    Before this extinction, marine animals were mostly filter feeders stuck in place on the seafloor, such as crinoids or "sea lilies." Afterward, the seas became far more complex with mobile creatures such as snails, urchins and crabs.

    The most likely final trigger for the end-Permian was again massive volcanism, this time at the Siberian Traps, which spewed as much as 2.7 million square miles (7 million square kilometers) of lava out, an area nearly as large as Australia.

    Recent evidence suggests, however, that the end-Permian may have been long in the making.

    The late Devonian extinctions

    The late Devonian extinction events were actually two sharp pulses of death about 360 million years ago, each just 100,000 to 300,000 years apart.

    Each pulse was accompanied by a massive drop in temperature, with the steaming seas of the Devonian—surface temperatures of which were about 93 degrees F (34 degrees C)—dropping to about 78 degrees F (26 degrees C), "and marine organisms would not have liked that at all," McGhee said. As to what caused these cold snaps, the ever-popular suspects are ash and dust kicked up by either astronomical impacts or massive volcanism.

    At that time, plants had made it onto land, as had spiders, scorpions and similar creatures. Right before the extinction events, the first proto-amphibians made it onto shore. However, the invasion of the so-called elpistostegalians—distant relatives of the coelacanth—"got wiped out by these extinction events," McGhee explained. "It wasn't until at least another 10 million years later that we got footprints from vertebrates on land again, this time from the ichthyostegalians, the proto-amphibians we're all descended from. Who knows how the world might have been different."

    The Ordovician-Silurian extinctions

    The earliest of the Big Five, the end-Ordovician or Ordovician-Silurian extinction events some 444 million years ago, are reckoned by many to be the second largest.

    These also consisted of a pair of die-offs, apparently involving massive glaciation and a resulting fall in sea levels. The cause of this glaciation remains a mystery, but one idea was that land plants actually caused it, pulling so much carbon dioxide out of the atmosphere that global cooling resulted, McGhee explained.

    Curiously, even though the end-Ordovician led to a huge loss of life, in a way it actually had very little impact on the persistence of lineages. Although the four other Big Five extinction events led to huge changes in which animals rose to prominence, the same animals that dominated before the end-Ordovician dominated afterward.

    Otherwise, "one neat thing about mass extinction events is that they're often reset buttons, where you change what dominates the globe," Conrad said. "You open the door to things like us to live."


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    Tuesday, March 11, 2008

     

    Vermillion Cliffs

    Photobucket

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    Photobucket

    arizona's natural wonders:
    http://gocalifornia.about.com/cs/arizonamenu/a/photo_az.htm



    http://www.geologytimes.com/Research/Dunes_climate_models_dont_match_up_with_paleomagnetic_records.asp

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    Wyoming - Devil's Tower National Monument

    Photobucket
    Devil's Tower

    Photobucket

    Back of Devil's Tower

    Devils Tower National Monument

    From Wikipedia, the free encyclopedia

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

    Devils Tower National Monument
    IUCN Category III (Natural Monument)
    Devils Tower National Monument
    Location Wyoming, USA
    Nearest city Gillette, Wyoming
    Coordinates 44°35′25″N 104°42′55″W / 44.59028, -104.71528 (Devils Tower National Monument)
    Area 1,346.91 acres (545.1 ha)
    Established September 24, 1906
    Visitors 386,558 (in 2004)
    Governing body National Park Service

    Devils Tower (Lakota: Mato Tipila, which means “Bear Tower”) is a monolithic igneous intrusion or volcanic neck located in the Black Hills near Hulett and Sundance in Crook County, northeastern Wyoming, above the Belle Fourche River. It rises dramatically 1,267 feet (386 m) above the surrounding terrain and the summit is 5,112 feet (1,558 m) above sea level.

    Devils Tower was the first declared United States National Monument, established on September 24, 1906 by President Theodore Roosevelt. The Monument's boundary encloses an area of 1,347 acres (5.45 km²).


    In recent years about 1% of the Monument's 400,000 annual visitors climb Devils Tower. The monolith is featured prominently in the 1977 film Close Encounters of the Third Kind.

    Name

    Devils Tower National Monument
    Devils Tower National Monument

    Tribes including the Arapaho, Crow, Cheyenne, Kiowa, Lakota, and Shoshone had cultural and geographical ties to the monolith before European and early American immigrants reached Wyoming. Their names for the monolith include: Aloft on a Rock (Kiowa), Bear's House (Cheyenne, Crow), Bear's Lair (Cheyenne, Crow), Bear's Lodge (Cheyenne, Lakota), Bear's Lodge Butte (Lakota), Bear's Tipi (Arapaho, Cheyenne), Tree Rock (Kiowa), and Grizzly Bear Lodge (Lakota).

    The name Devils Tower probably originated in 1875 during an expedition led by Col. Richard Irving Dodge when his interpreter misinterpreted the name to mean Bad God's Tower. This was later shortened to Devils Tower. [1]

    In 2005, a proposal to recognize these ties through the additional designation of the monolith as Bear Lodge National Historic Landmark met with opposition from Rep. Barbara Cubin, arguing that a "name change will harm the tourist trade and bring economic hardship to area communities" [2].

    Geological history

    Red sandstone and siltstone cliffs above the Belle Fourche River
    Red sandstone and siltstone cliffs above the Belle Fourche River

    Most of the landscape surrounding Devils Tower is composed of sedimentary rocks.

    The oldest rocks visible in Devils Tower National Monument were laid down in a shallow sea during the Triassic period, 225 to 195 million years ago. This dark red sandstone and maroon siltstone, interbedded with shale, can be seen along the Belle Fourche River. Oxidation of iron minerals causes the redness of the rocks. This rock layer is known as the Spearfish formation.

    Above the Spearfish formation is a thin band of white gypsum, called the Gypsum Spring Formation. This layer of gypsum was deposited during the Jurassic period, 195 to 136 million years ago.

    Created as sea levels and climates repeatedly changed, gray-green shales (deposited in low-oxygen environments such as marshes) were interbedded with fine-grained sandstones, limestones, and sometimes thin beds of red mudstone. This composition, called the Stockade Beaver member, is part of the Sundance formation. The Hulett Sandstone member, also part of the Sundance formation, is composed of yellow fine-grained sandstone. Resistant to weathering, it forms the nearly vertical cliffs which encircle the Tower itself.

    About 65 million years ago, during the Tertiary period, the Rocky Mountains and the Black Hills were uplifted. Molten magma rose through the crust, intruding into the already existing sedimentary rock layers.

    Theories of formation

    Mato Tipila (Devils Tower) at Devils Tower National Monument
    Mato Tipila (Devils Tower) at Devils Tower National Monument
    Devils Tower National Monument near the base
    Devils Tower National Monument near the base

    Geologists agree that Devils Tower was formed by the intrusion of igneous material. What they cannot agree upon is how, exactly, that process took place. Geologists Carpenter and Russell studied Devils Tower in the late 1800s and came to the conclusion that the Tower was indeed formed by an igneous intrusion. Later geologists searched for further explanations. Several geologists believe the molten rock comprising the Tower might not have surfaced; other researchers are convinced the tower is all that remains of what once was a large explosive volcano.

    In 1907, scientists Darton and O'Hara decided that Devils Tower must be an eroded remnant of a laccolith. A laccolith is a large mass of igneous rock which is intruded through sedimentary rock beds but does not actually reach the surface, producing a rounded bulge in the sedimentary layers above. This theory was quite popular in the early 1900s since numerous studies had earlier been done on a number of laccoliths in the Southwest.

    Other theories have suggested that Devils Tower is a volcanic plug or that it is the neck of an extinct volcano. Presumably, if Devils Tower was a volcanic plug, any volcanics created by it — volcanic ash, lava flows, volcanic debris — would have been eroded away long ago. Some pyroclastic material of the same age as Devils Tower has been identified elsewhere in Wyoming.

    Geologists agree that the igneous material intruded and then cooled as phonolite porphyry, a light to dark-gray or greenish-gray igneous trachyte rock with conspicuous crystals of white feldspar. As the lava cooled, hexagonal (and sometimes 4-, 5-, and 7-sided) columns formed. As the rock continued to cool, the vertical columns shrank horizontally in volume and cracks began to occur at 120 degree angles, generally forming compact 6-sided columns. (See also Devils Postpile National Monument and Giant's Causeway.)

    Until erosion began its relentless work, Devils Tower was not visible above the overlying sedimentary rocks. But the forces of erosion, particularly that of water, began to wear away the sandstones and shales. The much harder igneous rock survived the onslaught of erosional forces, and the gray columns of Devils Tower began to appear above the surrounding landscape.

    As rain and snow continue to erode the sedimentary rocks surrounding the Tower's base, and the Belle Fourche River carries away the debris, more of Devils Tower will be exposed. But at the same time, the Tower itself is slowly being eroded: cracks that form the columns are subject to water and ice, becoming larger. Rocks are continually breaking off and falling from the steep walls, and occasionally entire columns fall. Piles of scree — broken columns, boulders, small rocks, and stones — lie at the base of the tower, indicating that it once was larger than it is today.

    Recent history

    Fur trappers may have visited Devils Tower, but they left no written evidence of having done so. The first documented visitors were several members of Captain W. F. Raynold's Yellowstone Expedition who arrived in 1859. Sixteen years later, Colonel Richard I. Dodge led a U.S. Geological Survey party to the massive rock formation and coined the name Devils Tower. Recognizing its unique characteristics, Congress designated the area a U.S. forest reserve in 1892 and in 1906 Devils Tower became the nation's first national monument. All information signs and references use the name "Devils Tower".

    If Colonel Dodge intended the name "Devils Tower" to refer to a single devil, then proper grammar would indicate that the monument be called "Devil's Tower". It has been said that the apostrophe was omitted due to a clerical error on early governmental papers, and the version without the apostrophe became its legal, and therefore official, name[citation needed]. On the other hand, use of the plural "devils" may have been intended, either by Colonel Dodge or by the government agencies involved in establishing the monument; in which case there is no grammatical error in the name.

    Ponderosa Pine forest east of Devils Tower
    Ponderosa Pine forest east of Devils Tower
    East face of Devils Tower
    East face of Devils Tower

    On July 4, 1893, local rancher William Rogers became the first person to complete the climb after constructing a ladder of wooden pegs driven into cracks in the rock face. Technical rock climbing techniques were first used to ascend the Tower in 1937 when Fritz Wiessner reached the summit with a small party from the American Alpine Club. Today hundreds of climbers scale the sheer rock walls each summer; each lava column defines its own climbing routes, whose difficulties range from easy to some of the hardest in the world. On some routes the gap between columns is just narrow enough to bridge with stretched-out legs, so the climber ascends doing "the splits" all the way. All climbers must register with a park ranger before and after attempting a climb.

    The 1977 movie Close Encounters of the Third Kind used Devils Tower as a central plot element and as a location for its climactic scenes. It incorrectly gives the tower's coordinates as 40°36′10″N, 104°44′30″W.

    Native American folklore

    American Indian legends tell of six Sioux girls who were picking flowers when they were chased by bears. Feeling sorry for them, the Great Spirit raised the ground beneath the girls. The bears tried to climb the rock, but fell off, leaving their scratch marks on the sides.

    Another version tells of how two Sioux boys wandered far from their village when Mato the bear, a huge creature that had claws the size of teepee poles, spotted them, and wanted to eat them for breakfast. He was almost upon them when the boys prayed to Wakan Tanka the Creator to help them. They rose up on a huge rock, while Mato tried to get up from every side, leaving huge scratch marks as he did. Finally, he sauntered off, disappointed and discouraged. Wanblee, the eagle, helped the boys off the rock and back to their village. A painting depicting this legend by artist Herbert A. Collins hangs over the fireplace in the visitor's center at Devil's Tower.

    The Tower is sacred to several Native American Plains tribes, including the Lakota Sioux, Cheyenne and Kiowa. Because of this, many Indian leaders objected to climbers ascending the monument, as they felt this was a desecration. The climbers felt that they had a right to climb the Tower, since it is on federal land. A compromise was eventually reached with a voluntary climbing ban during the month of June when the tribes are conducting ceremonies around the monument. Climbers are asked, but not required, to stay off the Tower in June. According to the PBS documentary In Light of Reverence, approximately 85% of climbers honor the ban and voluntarily choose not to climb the Tower during the month of June. However, several climbers along with the Mountain States Legal Foundation sued the Park Service, claiming an inappropriate government entanglement with religion.[3]



    Saturday, March 08, 2008

     

    Patterns in Nature

    Patterns in Nature: Island Aerials

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