Glacier ice accumulation occurs through accumulation of snow and other frozen precipitation, as well as through other means including rime ice (freezing of water vapor on the glacier surface), avalanching from hanging glaciers on cliffs and mountainsides above, and re-freezing of glacier meltwater as . Accumulation is one element in the glacier mass balance formula, with ablation counteracting. With successive years in which accumulation exceeds ablation, then a glacier will experience positive mass balance, and its terminus will advance.