MSGID: 1:317/3 63178aef   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    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.   
      
      
    Wagon Tracks from the Old West?   
      
      September 06, 2022   
      
      
       Glacial striations   
      
      Photographer:  Brian Sauls   
      Summary Author:  Brian Sauls   
      No, these aren’t wagon tracks from the Old West. They’re  glacial   
      striations, or grooves, that were caused by abrasion from rock   
      fragments embedded in the base of an  alpine glacier that once   
      flowed in a valley near north-central Colorado’s  Green Mountain   
      Reservoir. These striated and polished rocks consist predominantly of   
       migmatite, which is an igneous/metamorphic rock exhibiting   
      alternating bands of light and dark-colored minerals that formed   
      approximately 1.8 billion years ago, during the  Precambrian Era.   
      They have the appearance of a marble cake and are well exposed due to   
      the relatively recent glacial erosion. Based on the  orientation of   
      the grooves, one can determine the direction that the glacier flowed.   
      Photo taken in the summer of 1981.   
      Photo details: Nikon FM camera; Vivitar 24mm f/2.0 lens; Kodak slide   
      film; digitized with Kodak slide scanner.   
      
      
      Green Mountain Reservoir Colorado Coordinates: 39.798056, -106.349444   
      
   Related EPODs   
      
       Wagon Tracks from the Old West?  First Light on the Circle   
      Cliffs Anticline  Mudcracks: Now and Then  Mantling on Utah’s   
      Hogback Ridge  Dendrite Inclusion in Opal  New Eddystone Rock   
       More...   
      
   Geology Links   
      
        *  Earthquakes   
        *  Geologic Time   
        *  Geomagnetism   
        *  General Dictionary of Geology   
        *  Mineral and Locality Database   
        *  Mohs Scale of Mineral Hardness   
        *  This Dynamic Earth   
        *  USGS   
        *  MyShake - University of California, Berkeley   
        *  USGS Ask a Geologist   
        *  USGS/NPS Geologic Glossary   
        *  USGS Volcano Hazards Program   
      
   -   
      Earth Science Picture of the Day is a service of the  Universities   
      Space Research Association.   
      
   https://epod.usra.edu   
       
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