This document discusses key concepts around folding and faulting in the Earth's crust. It describes how fold mountains like the Himalayas are formed by compressional forces causing rock layers to bend and crumple. The Himalayas were formed by the collision of the Indian and Eurasian tectonic plates around 50 million years ago. Faulting is caused by fractures in the crust along which rock masses move, and can result in normal faults, reverse faults, and transform faults. Block mountains and rift valleys can form from the vertical displacement of rock blocks along these fault lines. The Great Rift Valley extending through Africa provides an example of a rift valley formed by tectonic forces tearing apart the Earth's crust.

1. Chapter 9
Folding and
Faulting

2. Mountains
• Large landforms with steep slopes and heights of
above 600m
• Two types – fold mountains and block mountains
• They differ in formation, characteristics and appearance
Chapter 9: Folding and Faulting
Himalayas fold mountains

3. Folding
• Process in which rocks are bent and crumpled due to
compressional forces arising from the convergence of
two plates
• Results in the formation of fold mountains
Fold mountains
• Fold mountains are the highest mountains on the
earth’s surface
• Mount Everest is an example of a fold mountain
• It is the highest mountain in the world with a height of
8,850m and is part of the Himalayan mountain range
Chapter 9: Folding and Faulting

4. Chapter 9: Folding and Faulting
Mount Everest

5. Case study: Himalayas
• Mountain range in Asia between the Indian subcontinent
and the Tibetan Plateau
• Formed as a result of collision between the Indian
continental mass on the Indo-Australian Plate and the
Asian continental mass on the Eurasian Plate
• The two land masses were once separated by the
Tethys Sea
• When the two plates collided, the oceanic crust of the
Tethys Seas subducted beneath the Eurasian Plate.
• The Eurasian Plate was compressed and the
sedimentary layer was uplifted to form the Himalayas
• The Himalayas are considered young mountains as they
began to form about 50 million years ago, which is
relatively recent on a geological time scale
Chapter 9: Folding and Faulting

6. Chapter 9: Folding and Faulting
Indo-Australian Plate and
Eurasian Plate moving
towards each other
The sea disappears, the
Himalayas emerge from
the sea, convergence
continues
The sea bed is bent into a
series of folds

7. Types of folds
• Different types of folds are formed depending on the
strength of the compression
Chapter 9: Folding and Faulting
Symmetrical fold
Asymmetrical fold

8. Chapter 9: Folding and Faulting
Overthrust fold Nappe
Overfold Recumbent fold

9. Case Study: Blue Mountains of Jamaica
• The Blue Mountains of Jamaica are evidence of past folding
with much subsequent erosion of the rock strata
Chapter 9: Folding and Faulting

10. Faulting
• Process in which rock masses move along fractures in
the Earth’s crust
• These fractures are called faults
• Three types of faults
– Normal fault (vertical movement)
– Reverse fault (vertical movement)
– Transform fault (horizontal movement)
Block mountains and Rift Valleys
• A complex system of block mountains and rift valleys
may form as a result of varying vertical displacement of
different blocks of rocks
Chapter 9: Folding and Faulting

11. Chapter 9: Folding and Faulting
Normal fault
Reverse fault
Transform fault

12. Block mountains
• Uplifted blocks with steep slopes
• Formed by vertical displacement of rocks at normal faults
(tensional forces) and reverse faults (compressional forces)
Chapter 9: Folding and Faulting

13. Rift valleys
• Elongated areas that
have subsided between
two block mountains
• Deep, with steep walls
• Formed at normal faults
(by tension) and reverse
faults (by compression)
Chapter 9: Folding and Faulting
Formation of rift valley by tension

14. Chapter 9: Folding and Faulting
Formation of rift valley by compression
s

15. Case study: Great Rift
Valley
• Extends 4,800km from
Syria to Mozambique
• Consists of several well-
developed rift valleys,
some of which contain
lakes
• The valleys have
precipitous sides which are
fault scarps
• Formed by violent tectonic
forces that tore apart the
Earth’s crust
Chapter 9: Folding and Faulting

16. • During the tectonic movements, large parts of the crust sank
between parallel fault lines and molten rock was forced up in
volcanic eruptions
• Rifting continues today, with many active and semi-active
volcanoes and hot springs along the Rift
Chapter 9: Folding and Faulting