• Topography involves the examination of the Earth's land surface, encompassing features like craters, rivers, valleys, and mountains. In contemporary terms, topography primarily focuses on measuring and documenting elevation contours to generate a three-dimensional representation of the Earth's surface.

Introduction to Landforms:

• A landform refers to a feature on the Earth's surface shaped by various geomorphic processes (endogenic and exogenic) and agents like rainfall, wind, glaciers, and waves.
• Each landform possesses distinct physical characteristics, size, and nature. Over time, these landforms may undergo changes due to continuous geomorphic processes and agent activities.
• The ocean basins and continents are termed landforms of the first order. 
• Larger features on continents and ocean basins, such as mountains, plains, plateaus, continental shelf, continental slope, and submarine ridges, fall under landforms of the second order.
• Smaller landforms like a river valley, sand dune, or floodplain are classified as landforms of the third order.
• Some landforms are categorized as tectonic, while others are volcanic. The topographical features exemplify the interplay between geological factors and external forces acting on the Earth.

Cycle of Erosion

• The theory of the evolution of landform is known as the geomorphic cycle, sometimes known as the geographic cycle or cycle of erosion.
• William M Davis first proposed this idea, which postulated that landforms underwent a series of stages, from youth to maturity to old age, with each stage characterized by particular traits.
• Detachment, transport and deposition are the three main phases of erosion. Raindrops impact the disintegration of soil aggregates, after hydration and the scouring action of surface runoff both can cause soil particles at the soil surface to separate from the bulk of the soil body.
• During a runoff event, the movement of water and sediment or detached soil particles across the soil surface frequently exhibits discrete patterns that correspond to various forms of water erosion.

Classification of Landforms

Landforms Formed by Internal Factors

Formed by External Factors

• The Earth beneath our feet consists of three layers: the core, mantle, and crust. The crust and upper mantle collectively form the lithosphere.
• The lithosphere is not a single piece but is broken into several plates known as tectonic plates.
• These plates are in constant motion, leading to continuous changes. Major alterations in tectonic plates can result in the uplifting or sinking of the lithosphere.
• Landforms formed by internal factors involve both slow and sudden movements.

By Slow Movement

• Diastrophic forces arise from the movement of solid material within the Earth's crust. These forces encompass all processes that move, elevate, or build portions of the Earth's crust, falling under the umbrella of diastrophism.
•  Orogenic processes involve mountain building through severe folding, affecting long and narrow belts of the Earth's crust.
•  Epeirogenic processes entail the uplift or warping of large parts of the Earth's crust.
•  Earthquakes involve local, relatively minor movements.
• Plate tectonics involve horizontal movements of crustal plates.
• Slow movements can be classified as 
• Vertical Movements, primarily associated with the formation of continents and plateaus, also known as Epeirogenic movements.
•  Horizontal Movements act on the Earth's crust from side to side, causing orogenic movements, classified as forces of compression and forces of tension.

By Sudden Movement

• Lithospheric plate boundaries are susceptible to sudden geomorphic movements.
• Due to pressure caused by the pushing and pulling of magma in the mantle, plate boundaries become extremely unstable.
• Some movements cause abrupt changes in the crust. Examples include earthquakes and volcanoes, generating significant deformation in a short period.

Landforms Formed by External Factors

• External processes influencing landforms result from erosion or deposition.
• These processes encompass weathering, wind action, surface and groundwater, and sea ice.
• Forces acting on the Earth's surface due to natural agents like running water, glaciers, wind, and waves are categorized as external processes of landforms.

Landforms Formed by Rivers

• The impact of running water, particularly rivers, is extensive and surpasses other agents of gradation. Rivers originate in elevated landforms such as mountains, hills, and plateaus, receiving water from various sources like rain, glaciers, springs, and lakes.
• The primary functions of a river include erosion, transportation, and deposition. 
• Fluvial landforms are sculpted or built up by the continuous flow of water, comprising two components: sheet flow (overland flow as a sheet) and linear flow (overland flow as streams and rivers).
• Different stages of landscape development result from the action of water:
  • Youth: Early stages dominated by down-cutting, with broad, flat streams, marshes, swamps, and lakes.
  • Mature: Middle stages where streams cut their beds slower, and lateral erosion of valley sides intensifies.
  • Old: