Crustal Deformation

Question 1

Where does most deformation occur?

Answer 1

Along Plate Boundaries

Question 2

What type of stress is most often associated with convergent plate boundaries?

Answer 2

Compressional

Question 3

What type of fault is present when dominant displacement is horizontal and parallel to the trend
(direction) of the fault surface?

Answer 3

Strike-slip

Question 4

Which occurs when stress exceeds rock strength?

Answer 4

Deformation

Question 5

In what type of fault does the hanging wall moves up relative to the foot wall?

Answer 5

Reverse fault

Question 6

Which of the following correctly describes a fault?

Answer 6

It is a crack or fracture on the Earth’s crust (not sure)

Question 7

Which of the following are the factors that affect rock strength?

Answer 7

Rock type, temperature, time, and confining pressure

Question 8

What type of deformation results when the rock surpassed its elastic limit and breaks?

Answer 8

Brittle deformation

Question 9

Which feature is the characteristic of synclines?

Answer 9

It is a fold where the rock layers are warped downward that resulted from compressional stress.

Question 10

Which is the force that deforms rocks?

Answer 10

Stress

Question 11

Which type of deformation exhibits recoverable changes, where the rock will snap back to nearly
original size and shape when the stress is removed?

Answer 11

Elastic deformation

Question 12

Which type of differential stress pulls the rocks apart?

Answer 12

Tensional

Question 13

What refers to the factor that increases with depth and squeezes the materials in Earth’s crust that makes rock more stronger?

Answer 13

Confining pressure

Question 14

Refers to the changes in the shape or position of a rock body in response to differential stress?

Answer 14

Deformation

Question 15

Explain Compressional Stress

Answer 15

Differential stress that squeezes a rock mass as if placed in a vise is known as compressional stress.

Question 16

Explain Tensional Stress

Answer 16

Differential stress that pulls apart or elongates rock bodies is known as tensional stress.

Question 17

What type of stress is most often associated with divergent plate boundaries?

Answer 17

Tensional Stress

Question 18

Explain Sheer Stress

Answer 18

Differential stress can also cause rock to shear, which involves the movement of one part of a rock body past another. Shear is similar to the slippage that occurs between individual playing cards when the top of the deck is moved relative to the bottom.

Question 19

What type of stress is most often associated with Transform plate boundaries?

Answer 19

Sheer Stress

Question 20

Difference between Stress and Strain

Answer 20

• Stress is the force that acts to deform rock bodies.

* Strain is the resulting deformation (distortion).

Question 21

Explain the Elastic Deformation.

Answer 21

• When stress is applied gradually, rocks initially respond by deforming elastically.
• It acts like a rubber band,
• When the stress is removed, the bonds snap back to their original length.

Question 22

Explain Brittle Deformation.

Answer 22

• When the elastic limit (strength) of a rock is surpassed, the rock either bends or breaks.

Question 23

Explain Ductile Deformation

Answer 23

• Ductile deformation is a type of solid-state flow that produces a change in the shape of an object without fracturing.
• eg. a coin placed on a railroad track will be flattened but not destroyed.

Question 24

Explain the 4 factors that affects rock strength.

Answer 24

• Temperature
  
  • Higher temperature means higher malleability ( they deform by folding (ductile deformation))
  • Lower temperature means that rocks behave like brittle solids and fracture.
• Confining Pressure
  
  • Higher pressure means harder to break. Imagine a stack of bond paper being stacked together, it’s difficult to break.
• Rock Types
  
  • Igneous rocks and some metamorphic rocks have strong internal chemical bonds.
  • Sedimentary rock are weakly cemented and metamorphic rocks that contain zone of weakness behave in a ductile manner (eg. rock salt).
• Time
  
  • Rocks that are applied with stress over time tend to behave in a ductile manner (eg. books in a wood bookshelf).
  • Rocks that applied with stress suddenly will break.

Question 25

What are the common types of folds and the difference between them?

Answer 25

• Synclines are the downfolds

* Anticlines are the ones who arise by folding.

Question 26

What are folds?

Answer 26

Folds are geologic structures consisting of stacks of originally horizontal surfaces, such as sedimentary strata, that have been bent as a result of permanent deformation.

Question 27

What are he difference between symmetrical, asymmetrical, and overturned?

Answer 27

• Symmetrical limbs are mirror images
• Asymmetrical limbs are not mirror images
• Overturned (if one or both limbs are tilted beyond the vertical. Basically more than asymmetrical.

Question 28

How do faults form?

Answer 28

Faults form where brittle deformation leads to fracturing and displacement of Earth’s crust.

Question 29

Explain Dip-Slip Fault

Answer 29

Faults in which movement is primarily parallel to the inclination (also called dip) of the fault surface are called dip-slip faults. Geologists identify the rock surface immediately above the fault as the hanging wall block and the rock surface below as the footwall block.

Question 30

What are the types of Dip-Slip Faults?

Answer 30

Normal and Reverse

Question 31

Explain Normal Fault

Answer 31

• Dip-slip faults are classified as normal faults when the hanging wall block moves down relative to the footwall block.
• Normal faults are associated with tensional stresses that pull rock units apart, thereby lengthening the crust. This “pulling apart” can be accomplished either by uplifting that causes the surface to stretch and break or by horizontal forces that have opposing orientations.

Question 32

Explain Reverse Fault

Answer 32

• ip-slip faults in which the hanging wall block moves up relative to the footwall block are called reverse faults.
• Thrust faulting is most pronounced along convergent plate boundaries. Compressional forces associated with colliding plates generally create folds as well as thrust faults that thicken and shorten the crust to produce mountainous topography.

Question 33

Explain Strike-Slip Fault

Answer 33

• A fault in which the dominant displacement is horizontal and parallel to the trend (direction) of the fault surface is called a strike-slip fault.
• I think this is associated with shear stress.