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)

EXTENSION

COMPRESSION

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

Anticlinalmountain/ridge

Synclinalvalley

What’s this?

Synclinal mountain/ridge

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

normalnormal

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

Block mountainsBlock mountains

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

reversereverse

reversereverse

reversereverse

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

overthrustoverthrust

3. 3. Transcurrent (Strike-slip) FaultTranscurrent (Strike-slip) Fault

horizontal movementhorizontal movement

no fault scarpno fault scarp

Transcurrent Transcurrent

TranscurrentTranscurrentHEY! Whomoved my wood pile?!@*

TranscurrentTranscurrent

San AndreasSan Andreas