hummock

…beach, where it forms small hummocks. As these join together, foredunes are being built, and, if the beach is well-supplied with sand in the right area, several rows of dunes will be formed. When the sand is abundant, dunes will shift to adjacent low-lying plains and may bury fertile soils,…

The hummocky ground surface resembles karst topography in limestone areas. Thawing may result from artificial or natural removal of vegetation or from a warming climate.