By the hands of Nature

• Upper course of a river

  Part where it rapidly flows down along steep slopes from the place of origin, intense rate of erosion, less amount of sediments, no deposition, landforms like valley and waterfall
• Velocities of water flow, slope of the terrain, and rock structure affect the intensity of river erosion
• Waterfalls are generally formed at the upper course of rivers as a result of erosion
• Lateral erosion dominates as the river leaves the upper course, forming sinuous curves called meanders in the middle and lower courses of wide rivers
• Middle course of a river


  Stage where it flows through gently sloping foothills, erosion declines, deposition begins, more sediments carried down, features like meanders and oxbow lakes
• River erosion includes abrasion or corrasion where rock particles carried by the river wear down rocks
• Lower course of a river

  Stage where it flows through the plains, high quantity of water and sediments, active depositional processes, landforms like flood plains and deltas
• Course of a river

  1. Upper course

  2. Middle course

  3. Lower course
• River bed erosion is more prevalent in the upper course of the river
• Rainwater carries away loose rock particles from elevated surfaces, which is a form of weathering
• The earth's surface is a region where the lithosphere, the hydrosphere, and the atmosphere come into contact with each other
• Factors determining the flow of a river
• External forces cause both erosion and deposition
• Geomorphic processes help in the formation of landforms
• Rivers originate from springs at high altitudes and develop through the merging of numerous streams
• Erosion


  Transfer of rock particles formed by physical, chemical, or biological weathering processes from one place to another by external agencies such as running water, wind, glaciers, sea waves
• Land forms created by erosion and deposition


  • 'V' shaped valleys
  • Meanders
  • Oxbow lakes
  • Flood plains
  • Deltas
  • Stalactites
  • Stalagmites
  • Limestone pillars
  • Sea cliffs
  • Beaches
  • Mushroom rocks
  • Barchans
  • Glaciers
  • Cirques
  • U-shaped valleys
  • Moraines
• Mountains, valleys, plains, plateaus, waterfalls form various land forms on earth
• Varied landforms are created by continuous processes carried out by external agencies like running water, wind, glaciers, sea waves, etc.
• Deposition


  Materials deposited in low-lying regions by external agencies after erosion
• The place of origin of a river is called its source and the place at which it discharges into the sea or a water body is called the river mouth
• Human activities play a role in bringing changes to the earth's surface
• Weathering

  Physical and chemical change in rocks on the earth's surface
• Land forms created by underground water

  Rocks like limestone easily dissolve in rainwater which percolates to form underground water. Erosional and depositional landforms of underground water are mainly confined to limestone regions. These landform features are generally called Karst topography
• Sea cliffs are formed by the crumbling of sea-facing slopes due to wave erosion
• Many famous civilizations have originated along flood plains
• The North Indian plains, including the Ganga plain, Indus plain, and Brahmaputra plain, are extensive alluvial plains suitable for agriculture and inhabited by a large population
• Formation of stalactites and stalagmites in caves


  Water with dissolved limestone drips from cave roofs, forming stalactites. Deposits of lime on cave floors grow upward, forming stalagmites. Stalactites and stalagmites may merge with further growth
• Flood plains are formed when rivers overflow their banks during rainy seasons, covering extensive areas on both sides of the river. The deposition of alluvium along flooded banks causes the formation of flood plains
• Coastal landforms


  • Sea cliffs
• Crops cultivated in the North Indian plains

  • Wheat, maize, pulses, sugar cane, jute, etc
• Landforms created by underground water

  • Meanders, Oxbow lakes
• Flood plains are significant for agriculture
• Coastal landforms are created by erosional and depositional processes carried out by waves
• Formation of deltas


  The velocity of the river decreases near the river mouth, leading to the branching out of distributaries where sediments are deposited, forming triangular-shaped landforms called deltas
• Stacks

  • Isolated rock pillars formed from coastal rocks due to abrasion by waves
  • eg. stacks found along the coast of Thalassery in Kannur district
• Wind erosion in deserts

  1. Deflation: process of wind carrying away dry desert sands

  2. Abrasion: process of wind erosion causing rocks in deserts to get worn down
• Sea cliffs

  Steep hillocks facing the sea formed by the crumbling of the sea-facing slopes due to wave erosion
• Formation of snow fields on snow-clad mountains

  1. Continuous snowfall over years forming snow fields

  2. Snow-covered mountains extending over vast areas with kilometre-thick massive ice sheets that slowly crawl down forming glaciers
• Glacial landforms

  • Valleys formed by glacial erosion, cirques: armchair-like valleys formed by glacial erosion, U-shaped valleys carved out by glaciers