The Earth’s surface is not static.
Mountains rise, continents move, oceans widen, and landforms continuously change shape.
The branch of geography that studies the origin, evolution, and modification of landforms is called geomorphology.
To understand geomorphology, we must first understand:
- Forces acting inside the Earth
- Forces acting on the Earth’s surface
- Large-scale movement of continents and plates
This chapter explains these processes in a logical sequence.
Table of Contents
Endogenic and Exogenic Forces
Landforms are shaped by two major types of forces:
- Endogenic forces
- Exogenic forces
The difference between them is based on their origin.
Endogenic Forces
Endogenic forces are forces that originate inside the Earth.
These forces derive energy from:
- Earth’s internal heat
- Radioactive decay
- Pressure inside the Earth
Endogenic forces are responsible for building up relief features.
Types of Endogenic Forces
Endogenic forces operate in two main ways:
- Sudden movements
- Slow movements
Sudden Endogenic Forces
These forces act suddenly and cause immediate changes.
Examples:
- Earthquakes
- Volcanic eruptions
They can cause:
- Faulting
- Folding
- Sudden uplift or subsidence
These forces are highly destructive.
Slow Endogenic Forces
These forces act slowly over long periods.
Examples:
- Folding of mountains
- Warping of land
They result in:
- Formation of mountains
- Plateaus
- Large structural features
Slow endogenic forces are constructive in nature.
Exogenic Forces
Exogenic forces originate on or above the Earth’s surface.
They derive energy mainly from:
- Sun
- Gravity
Exogenic forces are responsible for wearing down landforms.
Processes of Exogenic Forces
Exogenic forces operate through the following processes:
- Weathering
- Erosion
- Transportation
- Deposition
These processes modify landforms created by endogenic forces.
Agents of Exogenic Forces
The main agents include:
- Running water
- Wind
- Glaciers
- Sea waves
Each agent creates characteristic landforms.
Relationship Between Endogenic and Exogenic Forces
Endogenic forces create relief, while exogenic forces destroy or modify relief.
Example:
- Mountains formed by endogenic forces are eroded by rivers and glaciers.
This balance continuously reshapes Earth’s surface.
Continental Drift Theory
The idea that continents were not always in their present positions was proposed by Alfred Wegener.
This idea is known as the Continental Drift Theory.
Main Idea of Continental Drift
According to this theory:
- All continents were once part of a single supercontinent called Pangaea
- Pangaea later broke into smaller landmasses
- These landmasses drifted apart to form present continents
Evidence Supporting Continental Drift
Wegener gave several evidences:
Matching Coastlines
The eastern coast of South America fits closely with the western coast of Africa.
This suggests they were once joined.
Geological Similarities
Rocks of same age and type are found on different continents.
Example:
- Brazil and Africa show similar rock structures.
Fossil Evidence
Similar fossils are found on continents now separated by oceans.
Example:
- Fossils of Mesosaurus found in South America and Africa.
Climatic Evidence
Evidence of glaciers found in present tropical regions.
This indicates continents have shifted positions.
Limitations of Continental Drift Theory
- Wegener could not explain how continents drifted
- No convincing mechanism was provided
Because of this, the theory was not fully accepted initially.
Plate Tectonic Theory
Plate Tectonic Theory explains both movement and mechanism of continents.
It is a more advanced and accepted theory.
Basic Concept of Plate Tectonics
According to this theory:
- Earth’s lithosphere is divided into large plates
- These plates float over semi-molten asthenosphere
- Plates move slowly over time
Plate movement causes major geomorphic features.
Types of Lithospheric Plates
Plates are classified into:
- Continental plates
- Oceanic plates
- Mixed plates
Movement of these plates leads to earthquakes, volcanoes, and mountain building.
Types of Plate Movements
There are three main types:
Convergent Plate Boundary
Plates move towards each other.
Results in:
- Fold mountains
- Volcanoes
- Earthquakes
Example:
- Himalayas formed by Indian and Eurasian plates.
Divergent Plate Boundary
Plates move away from each other.
Results in:
- Mid-ocean ridges
- Sea-floor spreading
Example:
- Mid-Atlantic Ridge.
Transform Plate Boundary
Plates slide past each other.
Results in:
- Earthquakes
Example:
- San Andreas Fault.
Importance of Plate Tectonic Theory
This theory explains:
- Formation of mountains
- Distribution of volcanoes
- Earthquake zones
- Continental drift
It unifies many geomorphological processes.
FAQs – GEOMORPHOLOGY (Exam-Focused)
What is geomorphology?
Study of landforms and processes shaping Earth’s surface.
Which forces originate inside Earth?
Endogenic forces.
Which forces wear down landforms?
Exogenic forces.
Who proposed Continental Drift Theory?
Alfred Wegener.
What was Pangaea?
A supercontinent containing all continents.
Why was Continental Drift Theory incomplete?
No mechanism for movement.
What does Plate Tectonic Theory explain?
Movement of plates and landform formation.
Which plate movement forms fold mountains?
Convergent movement.
Which forces depend on Sun’s energy?
Exogenic forces.
Why are earthquakes common near plate boundaries?
Due to plate movement.
Last-Moment Notes (Cheat Sheet)
GEOMORPHOLOGY
- Geomorphology → study of landforms
- Endogenic forces → internal
- Exogenic forces → external
- Endogenic → constructive
- Exogenic → destructive
- Sudden endogenic → earthquakes, volcanoes
- Slow endogenic → folding, warping
- Exogenic processes → weathering, erosion, deposition
- Continental Drift → proposed by Wegener
- Pangaea → single supercontinent
- Drift evidence → coastlines, fossils, rocks, climate
- Plate Tectonics → movement of lithospheric plates
- Convergent → mountains
- Divergent → ridges
- Transform → earthquakes