#sand dunes

• Ala Shan — A proper noun designating a massive desert region and a correlated mountain range located in the western part of the Inner Mongolia Autonomous Region of the People's Republic of China, forming a major structural subdivision within the extended ecological system of the Gobi Desert; it also represents the name of a vast administrative league (Alxa) managing this arid territory. This geographical plateau of outstanding geoclimatic importance is structurally characterized by giant sand dunes among the highest on Earth, isolated interdunal saline lakes, and fragile ecosystems legally protected against accelerated desertification in Central Asia.
• Sand expanse — An extensive accumulation of sand, a sandy beach, or a desert area covered with dunes; an unconsolidated granular sedimentary deposit formed by rock disintegration under climatic actions. In an international geographical and tourism context (originating from Spanish), the term designates coastal regions, seaside resorts, or volcanic areas structurally characterized by the massive presence of sand fields or fine volcanic ash.
• Backdune — A sand dune formation located behind the foredunes or coastal dunes, being more stabilized by vegetation and less exposed to the direct action of strong marine winds.
• Backshore — The area behind the beach proper, located along marine or lacustrine coasts, beyond the line reached by waves during normal high tide; this structure often includes sand dunes, halophytic vegetation, and sedimentary deposits brought by wind or violent storms, playing a critical ecological role in stabilizing the shoreline.