Transcript Diastrophism

Diastrophism
Results of plate tectonics:
1.volcanism
2.diastrophism
3.earthquakes
diastrophism:

Deformation of crust due to tectonic
stress:
• Folding (bending)
• Faulting (breaking and displacement)
Types of Stress and Strain
(Stress is force acting on rock; strain
is rock’s response to stress)

Compression (shortening)

Extension (stretching)
EXTENSION
COMPRESSION
Folding

Compressional stress causes rocks to
buckle and fold
• Anticline: arch-shaped fold
• Syncline: sink-shaped fold

Anticlines begin as ridges ; synclines
begin as valleys.

Differential erosion leads to:
• Anticlinal ridges and valleys
• Synclinal ridges and valleys

Differential erosion: less-resistant types of
rock strata will weather and erode more
rapidly than more-resistant rock strata
Anticlinal
mountain/ridge
Synclinal
valley
What’s this?
Synclinal mountain/ridge
Faulting

Rock is strained beyond ability to
remain intact; rock fractures; one
side is displaced with respect to the
other .
• Fault plane: surface along which 2 sides
move
• Fault scarp: cliff formed along fault face
Fault from Hebgen Lake, Montana
earthquake, 1959
What’s this?
Fault scarp
Types of Faults
1. Normal Fault:
from extensional stress
Vertical movement along an inclined fault plane
normal
Horst and Graben
(result of normal faulting)
Horst : upfaulted block
Graben: downfaulted block
Block mountains
2. Reverse Fault
from compressional stress
Vertical movement along inclined fault plane such
that one side rides up over the other.
often creates landslides
reverse
reverse
reverse
3. Overthrust fault


Reverse fault with very low angle
More horizontal than vertical movement
overthrust
3. Transcurrent (Strike-slip) Fault
horizontal movement
no fault scarp
Transcurrent
Transcurrent
HEY! Who
moved my
wood pile?!@*
Transcurrent
San Andreas