Sand dunes form when wind blows loose sand grains under gravity. Found in deserts, beaches, and semiarid regions worldwide. True dunes cover hundreds of square kilometres, some as large as France. Sand sheets are gently undulating sandy surfaces, up to several metres thick
Mammals are warm-blooded creatures that nurse young with milk. Birds are warm-blooded with feathers and wings for flight. Reptiles are cold-blooded with scales and lay eggs. Amphibians can live both on land and in water. Fish are aquatic creatures with gills and scales
Landforms are natural features shaping Earth's surface. Development influenced by tectonic activity, geological composition, and erosion. Climate and weather patterns affect erosion rates and sediment transport
Animal habitat includes food, water, and shelter. Most species can only survive in one habitat type. Some animals migrate seasonally between habitats
South America has 14 deserts covering about a seventh of Earth's surface. Deserts receive less than 10 inches of annual rainfall. Most deserts are sandy to icy and hilly to flat
Mount Damavand reaches 5,610 meters, highest peak in Iran and Middle East. Lut Desert holds record for highest surface temperatures on Earth. Maranjab Desert features shifting sand dunes reaching up to 50 meters. Mesr Desert offers clear night skies and sandboarding opportunities