First recorded in 1780–90; from French, from Savoyard dialect morêna “rise in the ground along the lower edge of a sloping field,” equivalent to mour(o) “mound, accumulation of earth” (from unattested murr- “mound, elevation,” apparently pre-Latin ) + -ena suffix of landforms, probably of pre-Latin origin; compare Upper Italian (Piedmont) morena “heap of organic detritus,” Spanish moreña “heap of stones, moraine”
A mass of till (boulders, pebbles, sand, and mud) deposited by a glacier, often in the form of a long ridge. Moraines typically form because of the plowing effect of a moving glacier, which causes it to pick up rock fragments and sediments as it moves, and because of the periodic melting of the ice, which causes the glacier to deposit these materials during warmer intervals.♦ A moraine deposited in front of a glacier is a terminal moraine. ♦ A moraine deposited along the side of a glacier is a lateral moraine. ♦ A moraine deposited down the middle of a glacier is a medial moraine. Medial moraines are actually the combined lateral moraines of two glaciers that have merged.