Deformation

A ___ is a circular fold where the youngest layers are in the middle and the oldest layers are on the outside. A) syncline B) monocline C) dome D) basin

D

Shear stress is a type of confining pressure.

FALSE

Fault-block mountains are created due to ________ faults. A) reverse B) strike-slip C) thrust D) normal

D

A ________ fault has a vertical fault plane and shows movement parallel to the orientation of the fault. A) reverse B) strike-slip C) thrust D) normal

B

Detachment faults are low-angle ________ faults. A) thrust B) normal C) reverse D) strike-slip

B

Folds form in ________ temperature-________ pressure environments. A) low-; low- B) high-; high- C) high-; low- D) low-; high-

B

How many hinge lines does a monocline have? A) One B) Two C) Three D) Four

B

How will rock salt likely respond when put under stress? A) It will fault B) It will bend or flow C) It will dissolve D) It will fragment

B

You are sitting in class when your professor begins talking about a dome with the inner layers dating back to the Tertiary and its outer layers dating back to the Permian. You immediately know this professor is wrong. What is your evidence? A) Domes don't have layers. B) Domes have the oldest layers in the middle, not the youngest. C) Now that we know the age of the layers, we would call it a syncline. D) Domes didn't exist back then.

B

______ refers to the changes in shape or position of a rock body in response to differential stress. A) Stress B) Deformation C) Compression D) Brittle failure

B

Faults form in ________ temperature-________ pressure environments. A) low-; low- B) high-; high- C) high-; low- D) low-; high-

D

Faults that exhibit both dip-slip and strike-slip movement are called ________ faults. A) thrust B) horst C) normal D) oblique-slip

D

How will strike and dip marks be oriented on the geologic map of a nonplunging syncline? A) Parallel dips with strikes pointing away from the center of the fold B) Strikes ringing the fold with the dips pointing toward the center C) Strikes intersecting, but no dips because of horizontal layering D) Parallel strikes with dips pointing toward from the center of the fold

D

The Basin and Range province is an extensional region in the American Southwest characterized by roughly parallel mountains ranges separated by broad, flat-bottomed valleys. What sort of structural features would you expect to find in this region?

Expected features would include normal faults, horsts, and grabens.

Joints are fractures in a rock created by tension and will demonstrate significant displacement.

FALSE

Rocks subjected to heat will be more likely to go through brittle deformation when stressed.

FALSE

Shearing produced fault zones in the deep crust and folding in the upper crust

FALSE

Explain how stress is different from strain.

Stress is a measure of how much force is applied over a given area. Strain refers to the resulting change in the shape of the rock.

A syncline is a downfold in rock where the youngest layers are in the middle of the fold and the youngest are on the outside

TRUE

Mountain ranges such as the Appalachians and the Himalayas are examples of mountains that formed as a result of ________ faulting. A) thrust B) normal C) strike-slip D) transform

A

Some of the most destructive earthquakes, such as the Haitian earthquake of 2010, occur along ________ faults. A) reverse B) strike-slip C) thrust D) normal

A

What is a fault? A) A fracture in a rock along which motion has occurred B) A stress fracture created by rocks stretching and pulling apart near the surface C) A solution pathway created by carbonic acid D) Foliation in a rock that acts as a plane of weakness

A

Which tectonic boundary would have many thrust faults associated with it? A) Convergent B) Divergent C) Transform

A

Which type of fault was responsible for the devastation associated with the 1906 earthquake in San Francisco? A) Transform B) Normal C) Reverse D) Thrust

A

You are a seismologist and are driving out to a location where a fault has recently shifted. When you arrive at the location, you see that the road you are driving on was constructed across the fault line. Because of slippage along the fault, the road ahead has been shifted to the left by 20 feet. What kind of fault is present? A) Left-lateral strike-slip B) Right-lateral strike-slip C) Thrust D) Normal

A

________ is the angle of inclination of the surface of a rock unit measured from a horizontal plane. A) Dip B) Faulting C) Strike D) Plunge

A

Movements along normal faults can produce alternating upthrown and down-dropped fault blocks. What are the names associated with these blocks, respectively? A) Synclines and anticlines B) Domes and basins C) Horsts and grabens D) Left-lateral and right-lateral

C

What is the difference between a reverse fault and a thrust fault? A) A reverse fault is the result of compression, and a thrust fault is the result of tension. B) A reverse fault lengthens the crust, whereas a thrust fault shortens the crust. C) A thrust fault has a fault angle of less than 45°, whereas the angle of a reverse fault is greater. D) Reverse faults are associated with convergent boundaries, and thrust faults are associated with transform boundaries

C

What is the difference between faults and joints? A) Joints are the result of compression, whereas faults are the result of tension. B) Joints are the result of earthquakes, and faults are the result of weathering. C) Joints form in place, whereas faults form because rock has moved. D) Joints form from external stress, and faults form from cooling.

C

Which of the following is an example of brittle deformation? A) Squeezing a rubber ball and seeing it bounce back B) Denting the fender of a car C) Throwing a hammer through a glass windowpane D) Pressing on a spring and seeing it rebound

C

Match the fault with the appropriate stress that caused it. A) Shear B) Compression C) Tension 12) Normal fault 13) Reverse fault 14) Strike-slip fault

12) C 13) B 14) A

Which tectonic boundary is associated with compressional stress? A) Convergent B) Divergent C) Transform D) Dip-slip

A

Which tectonic boundary would have many normal faults associated with it? A) Convergent B) Divergent C) Transform

B

Compare rock deformation in near surface environments to that deep within Earth's crust. Which deformation style will be more common in each location?

Brittle deformation is more common near the surface. Ductile deformation is more common at depth.

A ________ fault is created when the hanging wall moves up relative to the footwall. A) strike-slip B) normal C) reverse D) graben

C

A rubber band being stretched in preparation to fire across the room is an example of what kind of deformation? A) Brittle deformation B) Ductile deformation C) Elastic deformation D) Shear deformation

C

Which of the following are examples of fault-block mountains? A) Himalayas B) Rocky Mountains C) Basin and Range D) Alps

C

What is the outcrop pattern of a plunging syncline? A) The layers will close to a point in the direction of plunge. B) The layers will be oriented parallel to each other. C) The layers will intersect at right angles. D) The layers will open up in the direction of plunge.

D

What are the four factors that influence rock strength? Describe how they will affect the rock when it is under stress.

Higher temperatures make the rocks softer and more able to stretch or become malleable rather than shatter. Confining pressure squeezes rocks, making them harder to break. Certain rock types are more ductile than others, and others are more brittle. For example, rocks with intergrown mineral crystals are more likely to shatter in response to stress, where rocks that are weakly cemented or have zones of weakness are more likely to bend. Finally, time also influences the rocks' response to stress. Stress applied over a long period of time is more likely to result in ductile deformation, while stress applied over a short period of time is more likely to result in brittle deformation.

Over the course of the last couple of centuries, major businesses all over the world have spent a great deal of time and money searching for and studying structural geologic features in order to find deposits of petroleum. How would these structures trap the substances these companies are interested in?

Oil companies are searching for or have searched for structural features such as domes, anticlines, and inclined faults. These features can act as petroleum traps. For example, petroleum will migrate along permeable rock layers in an anticline, making its way up the layer because it is less dense. Once the petroleum reaches the top of the fold, the overlying layer may act as an impermeable boundary, not allowing any further migration upward and trapping the product.

Compare and contrast thrust faults and reverse faults.

Reverse and thrust faults are both the result of compressional stress. In both, the hanging wall moves up relative to the footwall. The main difference between these faults is that the fault plane of a thrust fault is much lower than that of a reverse fault, usually less than 30°. A thrust fault will also be responsible for significant crustal shortening, resulting in interesting situations where distant rocks are thrust on top of others, which not only shortens the crust but can result in violations of the law of superposition.

The Appalachian Mountains were formed when the North American continent collided with Africa to form the supercontinent Pangaea over 250 million years ago. What kind of tectonic boundary existed here? What sort of structural features would you expect to find in this region?

Since this is a convergent boundary, expected features would include folds such as anticlines and synclines as well as reverse or thrust faults.

Dip will always be 90° away from strike.

TRUE

Some strike-slip faults are big enough to accommodate movement between two tectonic plates.

TRUE

Strained geologic materials lose their original configuration during deformation.

TRUE

Despite not seeing the severe tectonic forces of the Rocky Mountains, the interior states of Illinois and Michigan have basins (the Illinois and Michigan basins). However, these basins formed in a different way. Explain how the Illinois and Michigan basins formed without significant tectonic influence.

The Illinois and Michigan basins formed through subsidence. These basins were the repositories of large accumulations of sediment, the weight of which caused the crust to subside.

Match the type of stress to the correct definition. A) Forces move toward each other. B) Forces slide past each other. C) Forces pull apart from each other. 1) Tension 2) Compression 3) Shear

1) C 2) A 3) B

Determine the type of stress necessary to produce each of the following geologic regions/features. (Note: Some choices will be used more than once.) A) Shear B) Tension C) Compression 4) Basin and Range province 5) San Andreas Fault 6) Grand Teton Mountains 7) Appalachian Mountains 8) Dakota Hogback

4) B 5) A 6) B 7) C 8) C

A) Rocks will change shape due to pressure but return to their original state when pressure is released. B) Rocks will shatter due to pressure. C) Rocks will change. 9) Elastic deformation 10) Ductile deformation 11) Brittle deformation

9) A 10) C 11) B

A(n) ________ fold has limbs that are tilted beyond the vertical to the point that the axial plane is horizontal, giving it the appearance of lying on its side. A) recumbent B) overturned C) plunging D) inverted

A

How do joints form in tectonic environments? A) Rocks near the surface are stretched and pulled apart. B) Hot rocks cool and contract. C) Water dissolves rock along fractures. D) Rock fractures through heating.

A

How will tensional force change a rock body? A) Stretch and thin the rock. B) Fracture the rock and grind the pieces alongside each other. C) Shorten and thicken the rock. D) The rock will not change.

A

Unbending a paper clip wire is an example of what kind of deformation? A) Brittle deformation B) Ductile deformation C) Elastic deformation D) Shear deformation

B

Which of the following best describes the age relationship of the layers in an anticline? A) Oldest on the outside of the fold, youngest on the inside B) Oldest on the inside of the fold, youngest on the outside C) Oldest materials thrust up on top of younger layers D) Horizontal bedding with the youngest layers on the top

B

How will compressional force change a rock body? A) Stretch and thin the rock. B) Fracture the rock and grind the pieces alongside each other. C) Shorten and thicken the rock. D) The rock will not change.

C

Which of the following scenarios would best indicate that a thrust fault is present at a location? A) The hanging wall of the fault has slipped down. B) Two parts of the same rock have been horizontally displaced by 20 feet. C) Cambrian-aged rocks have been shoved on top of Jurassic-aged rocks. D) The crust has lengthened, allowing a graben to slip down and create a pull-apart basin.

C

Which of the following statements best describes the relationship between the topography of a region and the underlying structural geology? A) Upfolds in the rock will make mountains and downfolds will make valleys. B) Downfolds in the rock will make mountains and upfolds will make valleys. C) There is no relationship between structures and topography.

C

________ is the compass direction of the line produced by the intersection of an inclined rock layer with a horizontal plane. A) Dip B) Angle C) Strike D) Plunge

C

Explain the role that confining pressure has on rock strength and how the rock deforms under pressure.

Confining pressure exerts equal pressure in all directions. As a result, the rocks are tightly compressed, which makes them stronger. When such rocks are subjected to stress, they will be more likely to bend rather than break.

What are slickensides? A) Joints made as an igneous rock cools and contracts B) Fractures made in a rock as a result of tensional stress C) Folded rocks along a convergent boundary D) Polished and striated surfaces made on fault blocks

D

Which of the following is the best description for structural geology? A) Study of intergrown mineral crystals in igneous rocks B) Study of sequences of sedimentary rocks and how their environments of deposition dictate how sediments are laid down C) Study of earthquakes and how they move through Earth's interior D) Study of rock deformation in response to tectonic forces

D

Which of the following rocks would be more likely to experience brittle deformation rather than ductile deformation when subjected to stresses that exceed their strength? A) Rock salt B) Sandstone C) Schist D) Quartzite

D

Explain the difference in orientation between a nonplunging anticline and a plunging anticline.

The hinge or axis of a plunging anticline will be tilted rather than horizontal, such as it would be in a nonplunging anticline.

Although the Valley and Ridge province of the Appalachians is characterized by intensely folded rock, it is not the structures themselves that are resulting in the ridges and valleys. What rocks make up the Valley and Ridge province, which ones make each landform (ridges or valleys), and why?

The rocks of the Valley and Ridge province are largely sandstone, limestone, and shale. Differential weathering and erosion created the ridges and valleys. Ridges are made of sandstone and valleys of limestone and/or shale.