Landforms and their Evolution — Class 11 Geography

A landform is a small to medium tract of the earth's surface; several related landforms make a landscape. Each landform has a history and evolves through stages comparable to youth, mature and old age. This chapter describes the erosional and depositional landforms made by the major geomorphic agents. Running water in humid regions is the most important agent: erosional forms include valleys, gorges, canyons, potholes, plunge pools, incised meanders and river terraces, while depositional forms include alluvial fans, deltas, floodplains, natural levees, point bars and meanders. Groundwater in limestone (karst) regions creates sinkholes, dolines, caves, lapies and limestone pavements, and deposits stalactites, stalagmites and pillars. Glaciers carve cirques, horns, arêtes and U-shaped (glacial) valleys, and deposit moraines, eskers, outwash plains and drumlins. Waves and currents shape coasts: high rocky coasts develop cliffs, wave-cut terraces, sea caves and stacks, while low sedimentary coasts develop beaches, bars, barriers, spits and lagoons. Winds in deserts cause deflation and abrasion, forming pediments, pediplains, playas, deflation hollows and mushroom rocks, and deposit sand dunes such as barchans, parabolic, seif, longitudinal and transverse dunes.