Santa Elena Canyon , the westernmost canyon in the park, was cut through faulted and uplifted Cretaceous limestone. The canyon walls reach a height of 1500 feet in places. Erosion produces rock falls in the canyons. Boquillas Canyon , the easternmost and longest canyon in the park, cuts through the Sierra del Carmen mountain range. Wind-blown sand is deposited along the side of Boquillas Canyon.
Wind carrying sand can abrade and polish bedrock surfaces.
Archeologists study corn-grinding pits and other traces left by prehistoric inhabitants along the Rio Grande. Yucca blooms in the desert.