An
esker,
eskar,
eschar, or
os, sometimes called an
asar,
osar, or
serpent kame, is a long, winding
ridge of
stratified sand and
gravel, examples of which occur in
glaciated and formerly glaciated regions of Europe and North America. Eskers are frequently several kilometres long and, because of their peculiar uniform shape, are somewhat like
railway embankments.