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| Massive landslide complexes within White Rock Canyon of the Rio Grande, below the town of White Rock. These landslides are mainly slumps, developed in Pliocene basalts and underlying Pliocene and Miocene sediments, and the capping basalts are back-tilted 35-45 degrees. Individual slumps have caused up to 0.5 km of retreat of the canyon rim. The slumps in this photo were largely emplaced before 50-60,000 years ago, although reactivation of at least one slump complex downriver caused repeated damming of the Rio Grande in the late Pleistocene and produced a series of lakes that were ~12-25 km long. The youngest major landslide event that has been identified occurred ~12,400 14C yr BP, during a wetter climate than is present today. Study of these landslides was undertaken to evaluate potential mass wasting hazards for waste sites at Los Alamos that are located close to the canyon rim. |
