In glacial geomorphology, what term describes a sinuous, elevated ridge composed of layered sand and gravel deposits?

An esker is a distinctive glacial landform characterized by its long, winding ridge structure composed of stratified (layeresand and gravel. These formations develop when meltwater streams flow through tunnels beneath or within a glacier, depositing sediment along their path. When the glacier eventually retreats and melts away, these sediment deposits remain as elongated ridges across the landscape. Terminal moraines are accumulated debris at the glacier's furthest extent, groundwater reservoirs (aquifers) are water-bearing rock layers underground, and glacial boulders (erratics) are large rocks transported and deposited by glacial ice far from their point of origin.