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Faulting. Location, Description and Formation of Rift Valleys and Block Mountains. What is a fault / faulting?. A fault is a crack or line of weakness in the Earth’s crust. Plate movements can cause the rocks in the crust to break and to be displaced.
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Faulting Location, Description and Formation of Rift Valleys and Block Mountains.
What is a fault / faulting? • A fault is a crack or line of weakness in the Earth’s crust. • Plate movements can cause the rocks in the crust to break and to be displaced. • When a fault is formed, some of the layers of rock on either side may move horizontally, upwards or downwards along the fault. • The movement of the layers of rock on either side of a fault is called faulting
Types of fault: Normal • this is when the hanging wall moves down with respect to the foot wall. Basically, the hanging wall is leaning on the foot wall but is actually the lower of the two rock blocks
Types of fault: Reverse • this is when the hanging wall moves up with respect to the foot wall. Basically, the hanging wall is leaning on the foot wall and is sitting leaning partly over top of the foot wall
Types of fault: Lateral (transform) • this is when rock moves horizontally past one another...much like sliding your hands back and forth across each other
Formation of Block Mountains (Horst) • Refers to a block of crust which is uplifted due to faulting • Faulting may cause tilting of a block of crust - “tilt block” • Formation by tension or compression • Tensional horst & Compressional horst • Deccan Plateau, Arabian Plateau, Brazilian Plateau
horst Formation of Horst by TENSION fault line
fault line Overhanging scarp removed by erosion horst Formation of Horst by COMPRESSION
Formation of Rift Valley (Graben) • Steep-sided trenches • formed by tension or compression • East African Rift Valley, Death Valley
Formation of Rift Valley (cont) fault line Rift valley
Group Work • Case Study 1: • The great African Rift Valley • How was it formed. • When was it formed? • Social, Economical and environmental impact it has to the people living there. • Case Study 2: • The San Andreas Fault • How was it formed. • When was it formed? • Social, Economical and environmental impact it has to the people living there.