reljef

Reljef is a term in several South Slavic languages for the three-dimensional form of the Earth's surface. It describes the arrangement and shape of landforms such as mountains, hills, plateaus, valleys and plains, and is a central concept in physical geography and cartography.

Reljef develops through tectonic forces that lift and deform the crust, volcanic activity, and long-term erosion and deposition by water, ice, and wind. Climate, isostatic adjustments and past glaciations also shape relief over geological time scales.

Relief is quantified and visualized with elevation differences and slope. Common measures include relief amplitude (the vertical difference between highest and lowest points in a region) and terrain ruggedness. Maps and models use contour lines, hillshading, digital elevation models (DEMs), and other remote-sensing data to represent relief.

Reljef is commonly described in terms of relief classes: high relief (rough, mountainous terrain), medium relief (hilly to rugged country), and low relief (flat or gently undulating plains). Micro-relief refers to small-scale surface roughness. The term is often used in contrast to topography, which refers to the mapping and portrayal of surface geometry.

Understanding relief informs hydrology, soil development, biodiversity, climate patterns, land-use planning, and hazard assessment. It varies greatly across regions and interacts with tectonics and climate to produce the diverse landscapes observed around the world.