.png)
Folding and Faulting (UPSC Geography Notes)
Overview: The Earth's crust is not a single solid piece — it is made of large plates that constantly move. When these crustal movements apply stress, the rocks either bend or break. This bending and breaking of rocks under stress are known as folding and faulting. Understanding these processes helps explain the formation of mountains, valleys, earthquakes, and many landforms — an important topic for UPSC Geography.
Table of Contents
- 1. Introduction
- 2. Folding – Meaning and Causes
- 3. Types of Folds
- 4. Major Fold Mountains of the World
- 5. Faulting – Meaning and Causes
- 6. Types of Faults
- 7. Difference Between Folding and Faulting
- 8. UPSC Quick Revision Notes
- 9. Previous Year Question
1. Introduction
The Earth's lithosphere (crust and upper mantle) is subjected to internal forces called endogenic forces. These forces can either cause the rocks to bend (folding) or break (faulting). The intensity and type of stress determine the resulting landform.
2. Folding – Meaning and Causes
Folding is the process by which the Earth's crust bends due to compressional forces. When horizontal forces act towards each other, the rock layers are pushed upward and downward to form folds.
Example: The Himalayas, Alps, and Andes are classic examples of fold mountains formed due to the folding of sedimentary rock layers.
Causes of Folding:
- Compression caused by plate movements.
- Accumulation of sediments in geosynclines (large depressions).
- Slow bending of rock layers under pressure and heat over time.
3. Types of Folds
Folds vary in shape and structure depending on the intensity of pressure and nature of rocks.
- 1. Anticline: An upward arch-like fold. The oldest rocks are at the core. (Example: Upward ridge)
- 2. Syncline: A downward trough-like fold. The youngest rocks are at the center. (Example: Valley between anticlines)
- 3. Symmetrical Fold: Both limbs dip equally in opposite directions.
- 4. Asymmetrical Fold: One limb is steeper than the other.
- 5. Overturned Fold: One limb is pushed over the other due to strong pressure.
- 6. Recumbent Fold: The fold lies horizontally due to extreme compression.
- 7. Isoclinal Fold: Both limbs are parallel and dip in the same direction.
4. Major Fold Mountains of the World
- The Himalayas – Asia
- The Alps – Europe
- The Andes – South America
- The Rockies – North America
- The Atlas Mountains – Africa
5. Faulting – Meaning and Causes
Faulting is the process of fracturing or breaking of the Earth’s crust due to tension, compression, or shearing forces. When stress exceeds the strength of rocks, they crack and move along fault lines.
Example: The Great Rift Valley of Africa and the San Andreas Fault in California are results of faulting.
Causes of Faulting:
- Horizontal and vertical movements in the Earth's crust.
- Excessive stretching or compression of rocks.
- Earthquakes caused by sudden fault movements.
6. Types of Faults
Depending on the direction of displacement, faults are classified as follows:
- 1. Normal Fault: Formed due to tension. The hanging wall moves downward relative to the footwall. (Example: Rift Valleys)
- 2. Reverse Fault (Thrust Fault): Formed due to compression. The hanging wall moves upward.
- 3. Strike-Slip Fault (Lateral Fault): Formed due to horizontal shearing forces. Rocks move sideways. (Example: San Andreas Fault)
- 4. Step Fault: Series of parallel faults forming a stair-like structure.
- 5. Block Fault: When blocks of crust move up or down between faults, forming rift valleys or horsts (uplifted blocks).
7. Difference Between Folding and Faulting
| Folding | Faulting |
|---|---|
| Occurs due to compressional forces causing bending of rock layers. | Occurs when rocks fracture or break due to stress. |
| Rocks bend without breaking. | Rocks break and move along fault lines. |
| Forms fold mountains like the Himalayas. | Forms rift valleys and block mountains. |
| Slow and plastic deformation process. | Sudden and brittle deformation process. |
8. UPSC Quick Revision Notes
Faulting – Breaking and displacement of rocks due to stress.
Major Fold Mountains – Himalayas, Andes, Alps.
Major Faults – San Andreas Fault, Great Rift Valley.
Fold → Bend, Fault → Break.
9. UPSC Previous Year Question
Q. The San Andreas Fault is an example of which type of fault?
(a) Normal Fault
(b) Reverse Fault
(c) Strike-Slip Fault
(d) Step Fault
Answer: (c) Strike-Slip Fault
Related Keywords
Folding and Faulting UPSC Notes, Structure of Earth’s Crust, Plate Movements, Fold Mountains UPSC, Fault Types Geography, Endogenic Forces UPSC, NCERT Geography Class 11 Notes.
Sources: NCERT – Physical Geography, GSI Reports, Britannica
