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Chapter 9 folding and faulting

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Raymond Douglas
Raymond Douglas

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.

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Chapter 9 Folding and Faulting
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
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
Chapter 9: Folding and Faulting Mount Everest
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
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
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
Chapter 9: Folding and Faulting Overthrust fold Nappe Overfold Recumbent fold
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
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
Chapter 9: Folding and Faulting Normal fault Reverse fault Transform fault
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
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
Chapter 9: Folding and Faulting Formation of rift valley by compression s
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
• 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

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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