We present results that unequivocally demonstrate that glacier moraines erode at their crests and accumulate sediment at their toes, resulting in significant landscape evolution over the lifespan of these landforms. We measured the concentration of cosmogenic ¹⁰Be in quartz from ~meter deep soil profiles dug at the crest, flank, and toe of two lateral moraines of different ages in the Mono Basin, CA. The concentrations of ¹⁰Be in the profiles show erosion at the moraine crests, and accumulation at their flanks and toes on the order of 0.01 – 0.1 mm/yr for the past 10-20,000 years. Additionally, ¹⁰Be concentrations increase downslope significantly. These results are consistent only with sediment transport models that begin with steep and sharp crested moraines that widen and flatten from meters to tens of meters over their lifespans.