Seven Devils Mountains, west-central Idaho
    The Seven Devils are dominated by Permian to Triassic (250-200 Ma) volcanic and sedimentary rocks.  These rocks were part of an island arc (above a subduction zone) offshore of North America 250-200 Ma ago.  They were shoved onto the ancient continental margin of North America at the end of the Cretaceous about 80 Ma ago.

    I don't have many rock pictures.   We did the 30 mile loop trail in July 2002, very nice flowers and weather.  Highly recommended.
 

From Horse Heaven Lookout at the southern end of the range looking north.
Breccia in next picture from talus slope.

Volcaniclastic breccia.  angular fragments of pale volcanic rock.

Notice square fragment near top of photo.  Fragments contain feldspar crystals.

The horizontally layered rocks are 16 Ma year old Columbia River basalt flows on opposite side of Hells Canyon of the Snake River.  Looking west, with Wallowa Mountains in background.  Wallowas made of same rocks as 7 Devils.  These old rocks can also be seen just under the layered lava flows.

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