Esker

Eskers are long, winding ridges of stratified sand and gravel which occur in glaciated and formerly glaciated regions of Europe and North America. They are frequently several miles in length and, because of their peculiar uniform shape, somewhat resemble railroad embankments[?]. Eskers are the deposits left by streams which flowed within and under glaciers; after the retaining ice walls melt away, the stream deposits remain as long winding ridges.