 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 - Johnsondale Potholes

   December 26, 2020

    6a0105371bb32c970b01157249c419970b
   Every weekend we present a notable item from our archives. This EPOD
   was originally published December 28, 2003.

   Provided and copyright by:  Tom McGuire
   Summary author:  Tom McGuire

   Inquiry is at the heart of science; for scientists as well as students.
   This group of holes is on a granite outcrop in the southern Sierra
   Nevada Mountains at the former logging camp of Johnsondale. I do not
   know the origin of these holes. Such open issues are sometimes called
   discrepant events.

   Two possibilities come to mind. They may be potholes caused by stream
   erosion. But they are numerous (about 20 of them) and uniform in size
   and shape. Native American matates, holes in rock used as natural bowls
   for grinding grain, are common in the southwest. (The shards of
   minerals in their bread products sometimes caused excessive tooth
   wear.) But these are quite deep and small. What do your students think?


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    More...

Geology Links

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     *  Geologic Time
     *  Geomagnetism
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     *  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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