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We determine minimum exposure ages for unstable outcrops at three sites in Amargosa Desert, southwestern Nevada, including a site at the southern end of Yucca Mountain. Varnish microlamination dating techniques provide minimum exposure ages of 12.5-36 k.y. for the unstable outcrops of welded tuff, including a 24 k.y. age for the south Yucca Mountain site. The youngest exposure age (12.5 k.y.) is found at the site located only 10 km from the Death Valley-Furnace Creek fault, suggesting outcrops may be more frequently modified when close to major active earthquake sources. A simplistic stability assessment of the south Yucca Mountain outcrops suggests peak ground accelerations (PGAs) may not have exceeded about 1g (uncertainty bounds 0.5-2g) in at least 24 k.y. A PGA of 1g is consistent with the predicted 24 k.y. return period PGAs from the near decade-old Yucca Mountain probabilistic seismic hazard (PSH) model, except for the ninety-fifth percentile and above. We gain confidence in our interpretations by additionally observing: (1) minimal damage to the south Yucca Mountain outcrops from a recent moderate earthquake that is estimated to have produced a PGA of less than 0.1g there (i.e., motions less than 0.5g do not significantly damage the outcrops); and (2) severe damage to similar volcanic outcrops associated with PGAs of the order 0.5-1g near a nuclear blast site from the 1960s. These observations support our suggestion that PGAs greater than 0.5-1g have not occurred at the south Yucca Mountain site for a time period of at least 24 k.y. Significant seismic events that substantially modify the outcrops and produce associated rubble fields may therefore occur on longer time scales.