• ES Picture of the Day 21 2020

    From Black Panther@21:1/186 to All on Sat Nov 21 11:00:34 2020
    EPOD - a service of USRA

    The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory
    captions and links exemplifying features within the Earth system. The
    community is invited to contribute digital imagery, short captions and
    relevant links.


    Archive - Acid Mine Drainage Chemistry

    November 21, 2020

    Acidminedrainagea copy

    Every weekend we present a notable item from our archives. This EPOD
    was originally published November 21, 2003.

    Provided and copyright by: Enver Murad, Bayerisches
    Geologisches Landesamt
    Summary author: Enver Murad

    Pyrite (iron sulfide) is a common constituent of lignites and coals.
    This pyrite oxidizes as it is exposed to the atmosphere in the course
    of mining, leading to the generation of sulfuric acid and dissolved
    iron (acid mine drainage). Besides the detrimental effect that the
    acidity has on the environment, this process often leads to an
    extensive generation of ochreous precipitates.

    In the example shown here, waters draining a sulfide-rich lignite seam
    in the Czech Republic precipitate under different conditions.
    Initially, a bright orange precipitate, consisting mainly of the
    sulfate-containing mineral schwertmannite, forms under acid conditions.
    After merging with alkaline waters (entering from the right-center of
    the picture), iron that has remained in solution precipitates almost
    instantaneously as ferrihydrite, a poorly-crystalline, sulfate-free
    iron oxyhydroxide, leading to a sudden change of precipitate color to
    reddish-brown. The variations in color can thus serve as indicators for
    the precipitate composition, and thereby for the conditions under which
    the precipitates formed.

    For more information on this locality, see the article by Murad and
    Rojík in American Mineralogist vol. 88, 2003, pp. 1915-1918


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    Geology Links

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    * Mohs Scale of Mineral Hardness
    * This Dynamic Earth
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    Earth Science Picture of the Day is a service of the Universities
    Space Research Association.

    https://epod.usra.edu

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  • From Black Panther@21:1/186 to All on Mon Dec 21 11:00:54 2020
    EPOD - a service of USRA

    The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory
    captions and links exemplifying features within the Earth system. The
    community is invited to contribute digital imagery, short captions and
    relevant links.


    Sunspot Sequence AR2781 in 8 days

    December 21, 2020

    #01 (3)

    Photographer: Paolo Bardelli
    Summary Author: Paolo Bardelli

    Sunspots appear as small dark areas on the surface of our Star.
    They’re linked to its intense magnetic field. Occurring in
    cycles of about 11 years (referred to as the solar cycle), their
    presence gives us an indication of the Sun activity. Sunspot
    temperatures are lower (cooler) than the Sun's surface
    ( photosphere).

    After a few years of very low solar activity, in a phase of a deep
    minimum between one cycle and another, a large group of spots called
    AR2781 recently appeared. Because of a spell of unusually fine
    weather, I was able to photograph this grouping for 8 days in a row.
    From the montage of images, the evolution and decay of this group (the
    largest spot could contain our Planet) can be easily followed. Also of
    note is the solar rotation, which curiously isn’t constant but varies
    from 25 days at the poles to 35 at the equator. Images taken at
    Albusciago, Italy, from November 5 - November 12, 2020.

    Photo Details: Images obtained with a Canon 6D camera mounted on a 203
    mm. Schmidt-Cassegrain telescope (f/10), equipped with an Astrosolar
    solar filter on the lens; processing with Photoshop and CC.
    * Albusciago, Italy Coordinates: 45.7395, 8.7939

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    Sun Links

    * NASA Solar Dynamics Observatory
    * NASA Solar Eclipse Page
    * NOAA Solar Calculator
    * The Sun-Earth Connection: Heliophysics
    * The Sunspot Cycle
    * Solar System Exploration: The Sun
    * The Sun Now
    * This Week’s Sky

    -
    Earth Science Picture of the Day is a service of the Universities
    Space Research Association.

    https://epod.usra.edu

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