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The Jornada Fault

Jornada Fault
(click for a larger version)
Jacob Thacker

Radium Springs, NM
— February 26, 2021

Faults are fractures in Earth’s crust where blocks of rock move in opposite directions relative to one another. The Jornada fault, pictured here near Radium Springs (north of Las Cruces, New Mexico), beautifully displays the juxtaposition of units from fault slip. Rocks and sediment on the west (left) side of the fault are river sediments from the Ancestral Rio Grande. Rocks and sediment on the east (right) side of the fault are composed of younger sedimentary units that deposited in the space formed as the east side dropped down relative to the west side. Depending on stress conditions in the crust, different types of faults form. The Jornada fault is a normal fault formed from extension of the crust within the Rio Grande Rift. Displacement of these units shows the Jornada fault slipped within the last 2 million years. Bushes and trees in the photo are approximately 1–2 m tall.

Jake Thacker, NMBGMR, Field Geologist