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| The Elephant Tusk is a prominant eroded remnant (stock) of a Tertiary-age volcano in the Chisos Mountains of Big Bend. Prickly pear cactus grow on a ledge of Boquillas Formation in the foreground. Midway in the distance are questas (escarpments of gently-inclined strata) consisting of marine, transitional, and non-marine sedimentary layers of the Aguja and Javelina formations of latest Cretaceous age. |
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