State by State


  • Specimen Number


  • Description

    Cross section of slab of highly vesicular basalt with vesicles aligned horizontally and diagonally to the upper left in this mounted specimen. Flow was possibly from right to left (?) in this orientation, as shown by tabular shape and diagonal of rising vesicles in zone to right.

  • Classification

    Igneous. Volcanic. Extrusive. Basalt. Vesicular

  • Location & Occurrence

    Likely from the Snake River Plain, which is similar to, but younger than the Columbia River Basalt Group (CRBG).  Its thick layered lava flows are flood basalts. Volcanic activity began 11-12 million years ago from a mantle plume, hotspot, and continues with the volcanic activity of Yellowstone today. The track of the hotspot can be seen in the brown color on the geological map, tracking from west southwest  to east northeast. Everything else is mountainous at this scale.

  • Geological Age

    Cenozoic, mainly Miocene postdating 11-12 million years ago (Ma).

  • Geoheritage

    Volcanism here is a continuation of the CRBG, the world's largest intact, well-exposed flood basalt province.  The plain is where most of Idaho's cities and its agricultural activity is.  The hazard of a Yellowstone's hot-spot supervolcano is best realized in the stone pavilion by this related specimen.

  • Links

    Link to State Geological Map from USGS.  Link to Idaho Geological Survey.  Link to USGS Columbia River Basalt Group.

  • Other

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Specimen stone for Idaho.
Closeup of Idaho Idaho Outline Map Idaho Geo Map