ch 10 crustal deformation

The limbs of an anticline will have dip angles pointing ____.

away from each other

Part C: How much displacement (in meters) has occurred?

0.4 meters

How does strain differ from stress?

Strain is the change in rock shape that results from stress, which is the force that deforms the rock.

What is the relative movement along a strike-slip fault?

The dominant displacement is parallel to the strike of the fault; Both blocks of rock move horizontally past each other.

Part F: What produces plunging folds?

a combination of folding and tilting

The Black Hills of South Dakota is a good example of which type of geologic structure?

dome

Part B: What are rocks below and above a fault called?

the footwall below and the hanging wall above

How are reverse faults different from thrust faults? In what way are they similar?

A reverse fault is steeper than a thrust fault; thrust faults have dips that are lower than 45 degrees. Both reverse and thrust faults result from compressional stress.

Part C: review the statements below, and indicate which are correct for the style of folding present in the Gigapan image.

At least one of the folds in this outcrop is asymmetrical; One side of the anticline dips more steeply than the other.

Which or statement or statements correctly describe brittle deformation and ductile deformation?

Both brittle deformation and ductile deformation are permanent; Brittle deformation describes a rock breaking as a result of stress, whereas ductile deformation describes a rock bending or folding as a result of stress.

________ is the angle of inclination of the surface of a rock unit measured from a horizontal plane.

Dip

Part A: Which of the following statements is true about erosion?

Erosion varies from place to place.

Movements along normal faults can produce alternating upthrown and down-dropped fault blocks. What are the names associated with these blocks, respectively?

Horsts and grabens

Where are the youngest rocks in a structural basin found?

In top view, the youngest rocks of a basin are near the center of the basin; The youngest rocks of a basin are on top of all the other rock layers.

How does a monocline form?

Movement along a steep fault in basement rock pushes up a portion of the ductile rock layers above it.

Part H: Imagine a fold has been eroded to a flat surface. In general, how would you know whether this fold is plunging?

Nonplunging folds look like straight lines at the surface, and plunging folds look like wavy lines.

What are slickensides?

Polished and striated surfaces made on fault blocks

Part E: Imagine a syncline has been eroded to a flat surface. How would the rock age change as you walked across that flat surface?

Rocks would be oldest on the edges and youngest in the middle.

Part D: Imagine an anticline has been eroded to a flat surface. How would the rock age change as you walked across that flat surface?

Rocks would be youngest on the edges and oldest in the middle.

Which of the descriptions below accurately describe the three various types of differential stress and the changes they can impart to rock bodies?

Shear stress, which moves one part of a rock body past another, changes rock shape and can break rocks apart; Compressional stress, which squeezes rock, generally shortens rocks horizontally and thickens them; Tensional stress, which pulls rock apart in opposite directions, horizontally stretches and lengthens rock bodies.

________ is the compass direction of the line produced by the intersection of an inclined rock layer with a horizontal plane.

Strike

Part B: Where do valleys tend to form in a landscape?

Valleys form where rock layers are easily erodible (soft).

Part C: What is a syncline?

a fold shaped like a right-side-up U

Part B: What is an anticline?

a fold shaped like an upside-down U

Part G: What does the term plunging fold mean?

a fold that is tilted down into Earth

Part A: Which type of force causes folding?

compressional force

Part D: Which type of force is responsible for reverse fault formation?

compressional force

Part A: What type of deformation is shown in the Gigapan image?

ductile

Part B: From the list of terms below, choose the ones associated with the fault you observed in the Gigapan image.

extension of the crust; tensional environment; normal fault

Part A: What is a fault?

fractures along which rocks move

Folds form in ________ temperature-________ pressure environments.

high-; high-

Faults form in ________ temperature-________ pressure environments.

low-; high-

Faults that exhibit both dip-slip and strike-slip movement are called ________ faults.

oblique-slip

The same type of stress that creates anticlines and syncline in some rocks will create ____ faults in rocks that exhibit brittle deformation.

reverse and thrust

____ rock units are most useful when mapping structures like anticlines and synclines.

sedimentary

Part E: Which type of force is responsible for normal strike-slip formation?

shear force

Part F: Which type of fault has NO vertical motion of rocks associated with it?

strike-slip fault

Part C: Which type of force is responsible for normal fault formation?

tensional force