chapter 9 folding and faulting
TRANSCRIPT
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Chapter 9Folding and Faulting
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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
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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
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Chapter 9: Folding and Faulting
Mount Everest
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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
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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
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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
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Chapter 9: Folding and Faulting
Overthrust fold Nappe
Overfold Recumbent fold
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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
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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
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Chapter 9: Folding and FaultingNormal fault
Reverse fault
Transform fault
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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
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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
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Chapter 9: Folding and Faulting
Formation of rift valley by compression
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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
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• 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