Endogenic Forces

Geomorphic Processes

Geomorphic processes are the natural activities that continuously shape, reshape, and modify the Earth’s surface. Over long periods of time, these processes are responsible for creating all major landforms such as mountains, valleys, plateaus, plains, and coastlines.

For someone new to this topic, it is important to understand that the Earth’s surface is not fixed or unchanging. Instead, it is constantly being altered by forces acting both inside the Earth and on its surface.

These processes are broadly divided into two categories:

• • Endogenic processes – processes that originate within the Earth
  • Exogenic processes – processes that act on the Earth’s surface

Examples:

• Endogenic processes:
  
  • Diastrophism (slow deformation of the crust)
  • Volcanism (movement of magma)
• Exogenic processes:
  
  • Weathering (breaking down of rocks)
  • Mass wasting (movement of rock materials down slopes)
  • Erosion (removal of materials)
  • Deposition (settling of transported materials)

Geomorphic agent :

A geomorphic agent is any natural moving force or medium that shapes the land by carrying materials from one place to another.

Common geomorphic agents include:

• • Running water (rivers and streams)
  • Glaciers (slow-moving ice masses)
  • Wind
  • Ocean waves and currents

These agents perform three main functions:

• • Erosion – removing material from one place
  • Transportation – carrying the material
  • Deposition – depositing it elsewhere

Endogenic forces

Endogenic forces are forces that originate from within the Earth. These are also known as internal forces.

They play a major role in shaping large-scale features of the Earth’s crust by causing:

• • Uplift (rise of land)
  • Subsidence (sinking of land)
  • Volcanic eruptions
  • Earthquakes
  • Folding and faulting of rocks

How are these forces generated?

These forces are driven by heat and pressure inside the Earth. This internal energy comes from several sources:

• • Radioactivity – heat produced by the breakdown of radioactive elements
  • Primordial heat – heat remaining from the Earth’s formation
  • Rotational and tidal forces – forces related to Earth’s movement

Because of this energy, the Earth’s crust is constantly in motion. These movements are mainly of two types:

• • Diastrophism (slow and gradual movements)
  • Sudden movements (rapid changes)

Diastrophism

Diastrophism refers to the slow, continuous deformation (change in shape) of the Earth’s crust over a long period of time.

In simple terms, it includes processes that:

• • Bend rocks
  • Fold layers of the crust
  • Warp (twist or distort) the surface
  • Fracture (break) the rocks
    

Key idea:

• Warping means bending or twisting out of the normal shape.

All processes that build up, move, or reshape large portions of the Earth’s crust fall under diastrophism.

Major types of diastrophic processes:

• • Orogenic processes – related to mountain formation
  • Epeirogenic processes – related to continent formation

Difference between the two:

These processes may also lead to:

• • Faulting (cracking of rocks)
  • Fracturing
  • Metamorphism of rocks (change in rock structure due to heat and pressure)

Epeirogenic or Continent forming movements [Vertical Movements]

Epeirogenic movements are slow, vertical movements of large sections of the Earth’s crust.

In simple words – The land may rise upward (uplift) or sink downward (subsidence) without much bending or folding.

Key features:

• • Affect large, stable parts of continents called cratons
  • Movements occur along the radius of the Earth, so they are also called radial movements

Types of vertical movement:

• • Uplift – land rises above its previous level
  • Subsidence – land sinks below its previous level
    

Uplift

Uplift is the process in which land rises upward, often becoming higher than sea level.

How do we know uplift has occurred?

Scientists look for the following evidence:

• Raised beaches (former shorelines now above sea level)
• Elevated sea caves
• Wave-cut terraces found at higher levels
• Marine fossils found far above sea level

Examples in India:

• Coastal areas of Kathiawar, Nellore, and Thirunelveli show raised beaches up to 15–30 meters above sea level
• Ancient port cities such as:
  
  • Coringa (near the Godavari delta)
  • Kaveripattinam
  • Korkai
    are now located inland, indicating that the land has gradually risen over time

Subsidence

Subsidence refers to the sinking or downward movement of land.

Evidence of subsidence includes:

• • Submerged forests (trees found underwater)
  • Drowned valleys
  • Structures buried below water level

Examples:

• In 1819, a part of the Rann of Kachchh sank due to an earthquake
• Peat and lignite deposits found below sea level in Thirunelveli and the Sunderbans
• The Andaman and Nicobar Islands became separated from the mainland due to sinking land
• Submerged remains have been found:
  
  • Near Mumbai
  • Along the Thirunelveli coast
• Parts of Mahabalipuram near Chennai are now underwater
• The Gulf of Mannar and Palk Strait are shallow due to recent submergence

Orogenic or the mountain-forming movements [Horizontal Movements]

Orogenic movements are horizontal movements of the Earth’s crust that result in the formation of mountains.

Key characteristics:

• • Act parallel (tangential) to the Earth’s surface
  • Closely related to plate tectonic movements

Types of forces involved:

• • Tensional forces
    
    • Pull rocks apart
    • Create cracks or fissures
  • Compressional forces
    
    • Push rocks together
    • Form folds and mountain ranges

Important point:

• These movements produce complex landforms, where it is often difficult to clearly identify structures.

Sudden Movements

Sudden movements are rapid and short-duration changes in the Earth’s crust.

Key features:

• • Occur mainly at tectonic plate boundaries
  • Caused by intense pressure and stress buildup
  • Result in quick and noticeable changes in landforms

Major types:

• Earthquakes
• Volcanoes

Earthquakes

An earthquake occurs when stress built up inside rocks is suddenly released, causing vibrations on the Earth’s surface.

Key effects:

• Ground shaking
• Possible outcomes:
  
  • Uplift of land
  • Change in river courses
  • Landslides
  • Tsunamis
  • Mass wasting (soil movement)

Example:

• The Chile earthquake (1822) caused about 1 meter uplift in coastal areas

Volcanoes

Volcanism refers to the movement of molten rock (magma) from inside the Earth towards or onto the surface.

A volcano forms when this magma escapes through:

• • Vents (openings)
  • Cracks (fissures) in the Earth’s crust

During a volcanic eruption, the following materials are released:

• • Lava (molten rock flowing on the surface)
  • Gases, such as:
    
    • Sulfur dioxide
    • Carbon dioxide
    • Hydrogen chloride
  • Steam
  • Pyroclastic materials (solid fragments of volcanic origin)

Pyroclastic flow: A pyroclastic flow is a fast-moving and extremely hot mixture of:

• • Hot gases
  • Volcanic ash
  • Rock fragments

Key features:

• Highly destructive and dangerous
• Can move at speeds up to 200 meters per second
• Burns and destroys everything in its pat