Moraines (World of Earth Science)
Moraines are glacial deposits of till (sediment) that are classified by their position relative to the glacial ice sheet. Moraines are classified as terminal moraines, lateral moraines, medial moraines, or ground moraines.
Moraines are formed of the sedimentary materials of varying sizes. Accordingly, they are poorly sorted and are essentially the sedimentary "dump" of material broken, dislodged, smashed, ground, and then deposited during the movement of glaciers.
End moraines form at the end of the glacial sheet. The end moraine that forms the maximum of glacial extent of glacial coverage (i.e., the farthest extent of "movement" of the glacier) is termed the terminal moraine.
Lateral moraines are deposits of till that accumulate along the lateral margins of the glacial sheet. As glacial sheets fuse, the corresponding fusion of lateral moraines forms a medial moraine.
Ground moraines form from deposits beneath the glacial sheet.
Moraines are geomorphologic features that can last long after glacial retreat (i.e., glacial melting) and moraines often form the base for varied and hilly landscapes in areas subject to periodic glaciation. Moraines can themselves be reshaped by subsequent glaciations and thus moraine patterns are often used to determine the extent and pattern of glaciations from which further information regarding climate changes can be derived.
See also Archeological mapping; Fjords; Ice ages; Ice heaving and ice wedging; Landforms; Landscape evolution; Topography and topographic maps