Lesson 3: Deformation of the crust Flashcards
forces tending to compress, pull apart or deform a rock
stress
squeezing, decreased volume
plates moving together (type of stress force)
compressive stresss
stretching, increased volume
plates moving apart (type of stress force)
tensional stress
change in shape
plates sliding past each other (type of stress force)
shear stress
adjustment to stress
strain
returns to original shape (strain type)
elastic strain
- molded or bent
- do not return to original shape (strain type)
plastic strain
rock cracks or breaks (strain type)
fracture strain
note: when drawing types of stresses, it is just one rock for compression, and tension. shearing looks like plate boundaries
if u remember, then nice
note: when drawing types of stresses, it is just one rock for compression, and tension. shearing looks like plate boundaries
if u remember, then nice
amount of force per unit area on a given material
stress
The process by which the shape of a rock changes in response to stress is called _____
deformation
defined as a bend in rock that is the response to
compressional forces
Most visible in rocks that have layering
fold
For plastic deformation to happen, there are lotsa factors. One is: pressure must not exceed the internal strength of the rock. If it does, ______occurs
fracturing
resulting deformation
strain
cause of deformation
stress
types of deformation
recoverable, small amounts of strain, doesn’t happen to rocks
Elastic
types of deformation
permanent; rocks flow as movement occurs along small structural defects.
Plastic
types of deformation
rock moves in opposite directions on either side of a break
rupture
what are the two main types of deformation?
Deformation by flow
Brittle deformation
site where rocks are exposed at the surface (honestly, this probs won’t appear in the exam)
outcrop
the angle of inclination of the bedding surface down off the horizontal
Dip
the trend or direction of the strata or the bearing of any horizontal line on the plane perpendicular to the direction of dip
Strike
– wavelike undulations caused by bending of rocks usually produced by horizontal compressive stresses
– occurs at great depths inside the Earth under great temperatures and pressures
folds (2nd definition)
a plane through a rock fold that includes the axis-divides the fold as symmetrically as possible
Axial plane
the ridge or place of sharpest folding
axis
1 of 2 parts of the fold-on either side of axis
limb
angle that fold axis makes with the horizontal
plunge
types of folds: arching or upwarping of rock layers
anticline
types of folds: down warping of rock layers
Syncline
types of folds: double flexure of rock layers
Monocline
types of folds: non-linear, anticlinal fold-beds dip away from central area in all directions
dome
types of folds: non - linear, synclinal fold-beds dip towards central area from all directions
basin
dips of opposite limbs of fold are approximately equal
symmetrical
asymmetrical fold with one limb tilted beyond vertical
Overturned
overturned fold with a horizontal axis
Recumbent
axis of fold penetrates into ground
Plunging
breaks in rock mass with no appreciable relative movement of rocks on opposite sides of break
Joints
breaks in rock mass where appreciable movement of rocks on opposite sides of the break has occurred
faults
block of rock immediately above fault surface
hanging wall
block of rock immediately below fault surface
Footwall
a fold in which the oldest rock layers are in the center of the fold
anticline
a fold in which the youngest rock layers are in the center of the fold
syncline
develops if the center of the fold moves from being once vertical to a horizontal position
recumbent fold
Extreme stress and pressure can sometimes cause the rocks to shear along a plane of weakness creating a
fault
combination of a fault and a fold
overthrust fold
up or down movement of two blocks
dip-slip faults
for drawing
when drawing right lateral transform faults, the top will be the one leaning towards the right side
deformation in the crust can either be ______ or ______
abrupt or gradual (creep)
sloping sides of a fold
limbs
bend where the two limbs meet
hinge
occur when tensional forces act in opposite directions and cause one slab of the rock to be displaced up and the other slab down
normal
On a graben fault causes
rift valleys
