Quiz 15: Geologic Structures

The definition of an open fold is one with a horizontal hinge line.

A geologic cross section represents a vertical slice through a portion of the Earth.

A joint is a fracture or crack in bedrock along which displacement has taken place.

A fault in which movement is predominantly horizontal and parallel to a strike is called a strike-slip fault.

A dome is a structure in which beds dip away from a central point.

Once stress exceeds the elastic limit the rock will deform in a permanent way.

All joints are a consequence of tectonic stress.

The axial plane divides a fold into top and bottom portions.

A syncline is a fold shaped like an arch, with the oldest rocks in the center.

Rifts are associated with converging plate boundaries.

The side of a fault above an inclined fault surface is the hanging wall.

Sheet jointing is a type of jointing due to compressional stress.

Strain is force per unit area.

A rock that behaves in a ductile manner will bend under stress but will not return to its original shape.

A thrust fault is a reverse in which the dip of the fault plane is at a low angle.

A normal fault results in crustal shortening.

A strike-slip fault can be right lateral or left lateral.

Dip angle is measured downward from the horizontal plane to the bedding plane.

The oldest rocks are found in the center of an eroded anticline.

Reverse faults can either shorten or lengthen the Earth's crust.

_____ may cause a change in orientation, location, and shape of a rock body. A) Deformation B) Strain C) Stress D) Structural forces E) Metamorphism

_____ stress results in a stretching or extension of material. A) Compressive B) Oblique C) Tensional D) Horizontal E) Parallel

Rocks typically exhibit _____ behavior at or near the surface where temperatures and pressures are low. A) extensional B) elastic C) compressive D) brittle E) plastic

The fact that a rock is folded or bent shows that it behaved as a _____ material. A) ductile B) elastic C) brittle D) solid E) rubbery

_____ folds have limbs that dip gently and the angle between the limbs is large. A) Recumbent B) Anticlinal C) Domes D) Structural E) Open

Geologists sometimes find valuable ore deposits by studying the orientation of ____, fractures or cracks in a rock body along which no displacement has occurred. A) dips B) faults C) joints D) strikes E) folds

_____ are usually associated with shortening of rock layers along convergent plate boundaries. A) Faults B) Folds C) Basins D) Metamorphic rocks E) Transforms

A ____ uses standardized symbols and patterns to represent rock types and geologic structures. A) correlation map B) geologic column C) Google Maps D) topographic map E) geologic map

_____ stress results in rocks being shortened or flattened. A) Elastic B) Compressive C) Tensional D) Orthogonal E) Horizontal

Stress is ______. A) force per unit of area B) change in volume C) regional metamorphism D) change in length to original length

If a deformed material recovers its original shape after stress is reduced, the behavior is __. A) brittle B) elastic C) plastic D) tensional E) compressional

An anticline is a fold shaped like a(n) ____ with the oldest rock in the center of the fold. A) cone B) umbrella C) arch D) W E) V

In cross section a structural basin looks like a ______. A) dome B) normal fault C) anticline D) bowl E) reverse fault

Where joints are oriented approximately parallel to one another a _____ can be defined. A) thrust fault B) overturned fold C) recumbent folds D) joint stress E) joint set

Normal and reverse faults are the most common types of _____. A) dip-slip faults B) strike-slip faults C) tensional faults D) compressional faults E) grabens

The side of the fault above the inclined fault surface is the ___. A) footwall B) hanging wall C) isoclinal wall D) plunging wall E) sheet wall

In a _____ fault the hanging wall block moves down relative to the footwall block. A) thrust B) reverse C) normal D) strike-slip E) compressional

A map symbol similar to the letter "T" is used to record ______ on a map. A) formation boundaries B) the location of fossils C) the orientation of a fold axis D) strike and dip E) the orientation of joints

If a bed strikes north it must ________. A) dip south B) dip either east or west C) be horizontal D) have a strike of 90 degrees E) have a strike of 270 degrees

On a surface leveled by erosion the pattern of exposed beds of a plunging fold resembles that of the letter __. A) X B) H C) V D) I E) T

The San Andreas Fault system can be described as _________. A) normal dip-slip B) reverse oblique-slip C) left lateral strike-slip D) right lateral strike-slip E) thrust dip-slip

For many geologists an active fault is one along which movement has taken place in the during the last ________ years. A) 1 million B) 500,000 C) 51,000 D) 15,000 E) 11,000

______ is the compass direction of a line formed by the intersection of an inclined plane and an imaginary horizontal plane. A) Altitude B) Dip C) Strike D) Orientation E) Attitude

A(n) ____ trap is one of the best structures for holding oil. A) monocline B) anticline C) basin D) synclinal E) reversed

A(n) ______ fault has both dip-slip and strike-slip components. A) reverse B) normal C) graben D) oblique-slip E) inclined

A thrust fault is ____. A) a strike-slip fault B) one in which the hanging wall moves down C) a variety of reverse fault D) a variety of a normal fault E) a response to horizontal tensional stress

A rock that behaves in a(n) ____ manner will bend under stress and does not return to its original shape. A) elastic B) brittle C) plastic D) rubber E) tactile

_____ are fractures in bedrock along which sliding movement has taken place. A) Joints B) Faults C) Planes D) Strikes E) Strains

The angle of dip is measured relative to _______. A) the horizontal B) the vertical C) north D) east E) the equator

A ______ stress is caused by forces pulling away from one another. A) shear B) tension C) perpendicular D) compressive E) fold

A(n) _____ is a structure in which beds dip away from a common central point, and the oldest rocks are found in the center. A) dome B) normal fault C) anticline D) syncline E) reverse fault

In a normal fault, the hanging-wall block has moved ______ relative to the footwall block. A) up B) down C) side to side D) up at a steep angle E) down at a steep angle

In a _____ fault, the hanging-wall block moves up relative to the footwall block. A) recumbent B) reverse C) normal D) strike-slip E) tensional

A(n) _______ fold has been overturned to such an extent that the limbs are essentially horizontal. A) overturned B) strike-slip C) recumbent D) dip-slip E) isoclinal

_____ are bends or wave-like features in layered rocks. A) Folds B) Strikes C) Warps D) Bends E) Flexures

A(n) _____ represents a vertical slice through the Earth. A) elevation model B) traverse C) map D) cross-section E) fold

The San Andreas fault in California is not a simple crack but ___. A) exists as a single line of breakage along most of its length B) is not connected to other fault systems C) a belt of broken and ground-up rock, usually a 100 m or more in width D) exists as a zigzag crack along most of its length E) shows little offset on the surface but greater offset below the surface

Collectively, the San Andreas fault system of California is a(n) _____. A) reverse fault B) right lateral strike-slip fault C) normal fault D) left lateral strike-slip fault E) oblique fault

According to plate tectonic theory, the San Andreas fault is a transform boundary that separates the North American plate from the _____. A) Cocos plate B) Pacific plate C) Eurasian plate D) Australian plate E) Caribbean plate

On a geologic map, a symbol that looks like a cross indicates ____. A) horizontal beds B) vertical beds C) overturned beds D) intersecting beds E) branching beds