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DiastrophismDiastrophism
Results of plate tectonics:Results of plate tectonics:1.volcanism1.volcanism
2.diastrophism2.diastrophism3.earthquakes3.earthquakes
diastrophism:diastrophism:
Deformation of crust due to tectonic Deformation of crust due to tectonic stress:stress:
• FoldingFolding (bending) (bending) • FaultingFaulting (breaking and displacement) (breaking and displacement)
Types of Stress and StrainTypes of Stress and Strain
((StressStress is force acting on rock; is force acting on rock; strainstrain is rock’s response to stress)is rock’s response to stress)
CompressionCompression (shortening) (shortening)
ExtensionExtension (stretching) (stretching)
FoldingFolding
Compressional stress causes rocks to Compressional stress causes rocks to buckle and buckle and foldfold• AnticlineAnticline: arch-shaped fold: arch-shaped fold• SynclineSyncline: sink-shaped fold: sink-shaped fold
Anticlines begin as ridges ; synclines Anticlines begin as ridges ; synclines begin as valleys.begin as valleys.
Differential erosionDifferential erosion leads to: leads to: • Anticlinal ridges and valleysAnticlinal ridges and valleys• Synclinal ridges and valleysSynclinal ridges and valleys
Differential erosionDifferential erosion: less-resistant types of : less-resistant types of rock strata will weather and erode more rock strata will weather and erode more rapidly than more-resistant rock stratarapidly than more-resistant rock strata
FaultingFaulting
Rock is strained beyond ability to Rock is strained beyond ability to remain intact; rock remain intact; rock fracturesfractures; one ; one side is displaced with respect to the side is displaced with respect to the other .other .
• Fault planeFault plane: surface along which 2 sides : surface along which 2 sides movemove
• Fault scarpFault scarp: cliff formed along fault face: cliff formed along fault face
Fault from Hebgen Lake, Montana Fault from Hebgen Lake, Montana earthquake, 1959earthquake, 1959
What’s this?
Fault scarp
Types of FaultsTypes of Faults
1. Normal Fault1. Normal Fault: :
from from extensionalextensional stress stress
Vertical movement along an inclined fault planeVertical movement along an inclined fault plane
Horst and GrabenHorst and Graben(result of normal faulting)(result of normal faulting)
HorstHorst : : up-up-faulted blockfaulted block
GrabenGraben: : down-down-faulted blockfaulted block
2. 2. Reverse FaultReverse Faultfrom from compressionalcompressional stress stress
Vertical movement along inclined fault plane such Vertical movement along inclined fault plane such that one side rides up over the other.that one side rides up over the other.
often creates landslidesoften creates landslides
3. Overthrust3. Overthrust fault fault
Reverse fault with very low angleReverse fault with very low angle More horizontal than vertical movementMore horizontal than vertical movement
3. 3. Transcurrent (Strike-slip) FaultTranscurrent (Strike-slip) Fault
horizontal movementhorizontal movement
no fault scarpno fault scarp
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