Esker
a long ridge built from diagonally layered sands and gravels with waving crest (Fig. 1) or a series of elongated hills created by meltwater flowing through subglacial (subglacial eskers) or englacial (englacial eskers) channels or along open crevices on a glacier’s surface (supraglacial eskers). Subglacial eskers are often located within subglacial trough. Most often, they are perpendicular to the front of the glacier or ice sheet, which created them.