 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.


 Madison Limestone in the Little Rockies of Montana

   May 17, 2021

    EPODbenson

   Photographer:  Rod Benson

   Summary Author:  Rod Benson
   These light-colored cliffs are made of nearly vertical layers of
    Madison limestone, formed from sediment deposited during the
    Mississippian Period about 340 million years ago. Thick deposits of
    corals, shells, and other forms of  calcium carbonate
   accumulated on the floor of a shallow tropical sea when this part of
   Earth’s crust was much closer to the equator. The hiker in the blue
   shirt provides a sense of scale.
   The sediment was deposited in horizontal layers, but about 60 million
   years ago magma worked its way up toward the surface, causing the
   Madison Limestone to be  domed upward. Eventually, the magma
   hardened, becoming igneous rock ( syenite porphyry), which forms the
   core of the mountain range. The doming occurred in an area about 15-20
   miles (24-32 km in diameter. Over time, most of the limestone above the
   igneous intrusion eroded away, leaving only the steeply- tilted edge of
   the  limestone dome that forms the cliffs shown in the photo. Many
   other similar outcrops can be found around the perimeter of the
    Little Rockies. Photo taken on March 19, 2021.

   Hays, Montana Coordinates: 47.9892, -108.6943


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    More...

Geology Links

     *  Earthquakes
     *  Geologic Time
     *  Geomagnetism
     *  General Dictionary of Geology
     *  Mineral and Locality Database
     *  Mohs Scale of Mineral Hardness
     *  This Dynamic Earth
     *  USGS
     *  USGS Ask a Geologist
     *  USGS/NPS Geologic Glossary
     *  USGS Volcano Hazards Program

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

https://epod.usra.edu
 
