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    Friday, December 08, 2006

     

    Ancient Vulcanism - Siberian Traps

    Siberian Traps

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    The Siberian Traps (Russian: Сибирские траппы) form a large igneous province in Siberia. The massive eruptive event spans the Permian-Triassic boundary and was essentially co-incident with the Permian-Triassic extinction event in what was one of the largest known volcanic events of the last 500 million years of Earth's geological history.


    Geographical extent

    Vast volumes of basaltic lava paved over a large expanse of primeval Siberia in a flood basalt event. Today the area covered is about 2 million km² and estimates of the original coverage are as high as 7 million km². The original volume of lava is estimated to range from 1 to 4 million km³.

    The area covered lies between 50 and 75 degrees north latitude and 60 to 120 degrees east longitude. The volcanism continued for a million years and spanned the P-Tr Boundary. There is no firm evidence that this event caused (or helped cause) the Permian extinction, but the timing of the two events is provocative.

    Reason for formation

    The source of the Siberian Traps basalt is considered to be a mantle plume which impacted the base of the crust and erupted through the Siberian Craton. Helium isotope geochemistry from the basalts indicates a plume origin. The scientific debate continues, however.

    Siberian Traps and nickel

    The Siberian Traps are considered to have erupted via a vent at Norilsk in Siberia, and the giant Norilsk-Talnakh nickel-copper-palladium deposit formed within the magma conduits which formed the eruptive centre.

    External links





    Small example of lava outpouring from fissure vent; Outpouring at Siberian Traps huge and prolonged. Figure Caption: Photograph of the Pu'u 'O' fissure eruption, Hawai'i, in July 1986. This illustrates the type of eruption event that may have produced the Siberian flood basalts. However, the eruption volumes and rates would have been substantially greater in Siberia. Note the substantial gas clouds (containing sulfur dioxide, carbon dioxide, and water vapour) issuing from the vent. (Photo copyright USGS.)
    http://www.le.ac.uk/gl/ads/SiberianTraps/Introduction.html

    End Permian Volcanism


    The Siberian Traps were the largest volcanic eruption in Earth history and they occured right at the same time as the largest extinction event in Earth history.

    Co-incidence?


    It is engrained in everyone from an early age that volcanic eruptions are dangerous to life so the Siberian Traps could indeed hold the key to explaining the Permo-triassic extinction event

    What are they and how did they form?

    The Siberian Traps are a large igneous province were a result of a mantle plume. A mantle plume is a giant pulse of heat that rises towards the surface from the core/mantle boundary. Plumes are easily indentified but not well understood and they are believed to be part of a cooling mechanism for the core. Whatever their cause a large amount of anomalously hot material rises to the surface and ponds below the earths crust in a head which can be 1000's of km wide and 100's of km deep.

    image credit: Walter S. Kiefer and Amanda Kubala. LPI

    This pond of basalt magma penetrates the crust through fissures pouring gigantic amounts of basalt onto the surface. Events like this are known as Flood Basalt eruptions and fortunately are very rare with only 8 have occurred in the last 250 million years.

    Where are they and how big are they?

    They are centred around the siberian city of Tura and also encompass Yakutsk, Noril'sk and Irkutsk. Present coverage including associated pyroclastics is just under 2 million square kilometres which is an area greater than that of Europe. Estimates of the original volume of the traps range from 1 million cubic km up to 4 million cubic km. According to P.B.Wignall in his 99 paper, "the distribution of lavas suggests that they do not constitute a single continuous province but rather the amalgamation of several subprovinces.

    The eruptions lasted at full intensity for about a million years which coincides with the extinction. The most accurate dating method available at the moment is Argon - Argon radiometric dating which still contains sufficient uncertainties to conclusively prove the exact timing.(Read more: http://palaeo.gly.bris.ac.uk/Palaeofiles/Permian/SiberianTraps.html )


    Gigantic massifs created by vast outpouring of flood basalt lava - vulcanism



    http://www.le.ac.uk/gl/ads/SiberianTraps/Index.html

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    Comments:
    Very Interesting... thank you
     
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