Crustal Deformation

Question 1

Define Stress

Answer 1

The forces applied to objects, that cause rock deformation. Pushing or Pulling

Question 2

Define Strain

Answer 2

Is the deformation resulting from applied stress

Question 3

What are the 3 forces of stress

Answer 3

Compression: Convergent Zones
Tension: Divergent Zones
Sheer: Transform Zones

Question 4

Styles of Deformation

Answer 4

Ductile: deformation is a solid that flows, stretches or bends with applied stress
Brittle: is where solid fractures, breaks or snaps with applied stress
Elastic: reverses when stress is removed

Question 5

What do brittle responses to stress result in

Answer 5

Faults

Question 6

Define Faults

Answer 6

a fracture in bedrock along which rock on one side has moved relative to the other side.

Question 7

Define Strike and Dip *****possible test question

Answer 7

Geologists use a special symbol called strike and dip to represent inclined beds. Strike and dip map symbols look like the capital letter T, with a short trunk and extra-wide top line. The short trunk represents the dip and the top line represents the strike. Dip is the angle that a bed plunges into the Earth from the horizontal. A number next to the symbol represents dip angle.

Question 8

What do ductile responses result in

Answer 8

Folds which are permanent wavelike deformations in layered rocks.

Question 9

What do Compressive, tensional and shear forces result in

Answer 9

Compressive: reverse faulting
Tensional: Normal Faulting
Shear: Strike and Slip Faulting

Question 10

What are strike and slip faults apart of

Answer 10

Transform boundaries, plates moving next to eachother.

Question 11

What are the blocks on either side of a fault called*** possible question

Answer 11

Any rocks above the fault are called: Hanging wall

Any rocks below the fault are called: the Footwall

Question 12

What occurs when something folds

Answer 12

A ductile deformation, this occurs at relatively high temperatures and pressures, however at some point the rock will break.

Question 13

Define Anticline and Syncline

Answer 13

Anticline: is a fold with convex side upward (therefore oldest layers in the middle)
Syncline: is a fold with the concave side upward (therefore youngest layers in the middle)
Usually anticlines and synclines alternate in the field

Question 14

Define Symmetrical folds

Answer 14

both limbs dip symmetrically away or towards axial planes

Question 15

Anatomy of the fold

Answer 15

a fold is a stack of originally planar surfaces, such as sedimentary strata, that are bent or curved during permanent deformation.

Question 16

Define Asymmetrical folds

Answer 16

A fold is pushed over, limbs dip in opposite directions but at different angles. The axial plane becomes tilted.

Question 17

Defined overturned folds

Answer 17

a fold is pushed farther over. Limbs dip in same direction but at different angles.
The axial plane approaches horizontal

Question 18

Define the two special folds, Structural Dome and Structural Basin

Answer 18

Structural Dome: anticlinal circular structure

Structural Basin: Synclinal circular structure

Question 19

Define the Thrust Fault

Answer 19

It is a special case of reverse fault

Question 20

Define Strike Slip Fault and the different laterals

Answer 20

motion is horizontal only. No vertical component
Rock units slide past each other.
Right lateral: opposite side moves to the right
Left lateral: opposite side moves to the left

Question 21

What is the most famous strike slip or transform fault in North America

Answer 21

San Andreas

Question 22

Define normal fault

Answer 22

Normal faults move by a vertical motion where the hanging-wall moves downward relative to the footwall along the dip of the fault. Normal faults are created by tensional forces in the crust. Normal faults and tensional forces commonly occur at divergent plate boundaries, where the crust is being stretched by tensional stresses

Question 23

Define reverse fault

Answer 23

In reverse faults, compressional forces cause the hanging wall to move up relative to the footwall. A thrust fault is a reverse fault where the fault plane has a low dip angle of less than 45°. Thrust faults carry older rocks on top of younger rocks and can even cause repetition of rock units in the stratigraphic record.