Chapter 10

A plunging fold

A V outcrop pattern indicates

Syncline

A fold in rock that bends downward to form a valley.

Monocline

A fold in which both limbs are horizontal or almost horizontal.

Faults

Breaks in Earth's crust where rocks have slipped past each other.

Elastic deformation

Glacioisostatic rebound is an example of what type of deformation?

They describe different directions of movement along a fault plane

How do dip-slip and strike-slip faults differ from one another?

around a fossil, between minerals, and along bedding planes

Rock joints will form at a point of weakness such as:

29,000 ft

Roughly how tall is Mount Everest?

Shear Stress

Strike-slip faults are caused by __________ acting on the crust.

The North American plate

The magma of the Cascades is generated by partial melting of which plate?

limbs

The sides of the geologic structure called 'folds' are represented by the term:

Elastic, ductile, and brittle

The three types of strain are:

False

TorF: A dome is a circular syncline.

plunging folds

What does an outcrop pattern of Vs indicate?

Basin

What type of structure is in Figure 5?

Geological Map

a representation of a region on which is recorded earth information (e.g.,the distribution, nature, and age relationships of rock units and the occurrences of structural features, mineral deposits and fossil localities

Volcanic Mountains

mountains that form when molten rock erupts onto the earth's surface

Footwall Block

rock surface below the fault

Folds

A bend in rock that forms where part of Earth's crust is compressed. the result of compressional stresses acting over long periods

Strain

A change in shape and/or volume of a rock caused by stress. Takes place in three stages:

Syncline

A downward fold in rock formed by compression in Earth's crust.

Fault-Block Mountains

A mountain formed by blocks of rock uplifted from normal faults.

The hanging wall is displaced upward along the fault plane

A reverse fault is formed when:

North American and Pacific plates.

A transform boundary marks the contact between the:

Strike-Slip Fault

A type of fault where rocks on either side move past each other sideways with little up or down motion.

Normal Fault

A type of fault where the hanging wall slides downward; caused by tension in the crust.

Reverse Fault

A type of fault where the hanging wall slides upward; caused by compression in the crust.

Anticline

An upward fold in rock formed by compression of Earth's crust.

Dip

Angle in degrees between a horizontal plane and an inclined plane, measured down from horizontal in a plane perpendicular to the strike.

Deformation

Any alteration of shape or dimensions of a body caused by stresses, thermal expansion or contraction, chemical or metallurgical transformations, or shrinkage and expansions due to moisture change.

Fracture (brittle deformation)

Any break or rupture in rock along which no appreciable movement has taken place

20 Million Years Ago

Approximately how long ago did subduction end in the Los Angeles area?

Shear Stress (crust displacement)

Causes a body of rock to be distorted side-to-side

Strike

Compass direction of a horizontal line that marks the intersection of an inclined plane with Earth's surface.

Dip-Slip Faults

Fault with the slip vector oriented along the dip direction of the fault surfac

Are the product of tensional stress

Fault-block mountain systems are the product of what kind of stress?

Plunging Anticline

Figure 6 is what type of structure?

principle of original horizontality

Horizontal layers that eventually form sedimentary rocks can be created by sedimentary particles in water settling uniformly when acted upon by gravity. The principle that describes this process is the:

Stretching

How is tensional stress expressed?

Center; Towards

Rocks dip towards _______ (center, outside) of a basin because rocks always dip ______ (towards, away from) the youngest rocks.

Subduction Zone

The Cascade Mountains developed above a(n):

Are a volcanic arc

The Cascade Range...

A mountain belt

The North American Cordillera is an example of:

Isostasy

The balancing of the downward force of the crust and the upward force of the mantle.

Foot Wall

The block of rock that forms the lower half of a fault.

Hanging Wall

The block of rock that forms the upper half of a fault.

Stresses

The forces that cause deformation

A

The oldest rock unit in Figure 6 is?

Compressional, Tensional, Shearing

The three types of stresses are:

True

TorF: A strike-slip fault is a fault in which the direction of movement is horizontal and parallel to the strike of the fault.

True

TorF: Both continental and oceanic crust are exposed to stress.

True

TorF: Cold rock tends to be brittle and therefore fractures more easily.

False

TorF: Earth's crust is extremely rigid. This rigidity disallows it to be pulled or bent.

True

TorF: Fault-block mountains are characterized by tensional stress, crustal thinning, and normal faulting.

True

TorF: For any inclined fault, the block that hangs above the fault plane is the hanging wall block and the block below it is the footwall block.

False

TorF: For ductile deformation of rock to occur, the deformation must take place at a rapid rate.

True

TorF: Horsts and grabens are typical in a region of crust that is being pushed upward from below, causing regional extension.

False

TorF: Jointed rocks block groundwater from permeating Earth's crust.

False

TorF: Once a fracture has occurred, further stress can change the volume of the rock.

False

TorF: Reverse faults develop in brittle rocks that are exposed to tensional stress.

True

TorF: Strike is measured using a compass that indicates the orientation of the line relative to north.

True

TorF: The Himalayan mountains were formed as a result of large compressional stresses in the crust at convergent margins.

True

TorF: The San Andreas Fault is a right lateral strike-slip fault.

False

TorF: The San Andreas Fault is located primarily on the Nevada and Arizona border.

False

TorF: The crust at Earth's surface is relatively hot and is therefore also brittle.

Isostatic Adjustment

Vertical movement of sections of Earth's crust to achieve balance

It fractures

What happens when a material stretches just beyond its limit of ductile deformation?

Tranform plate boundaries

What kind of boundary is known to experience shear stress?

Tensional Stress

What kind of stress leads to the thinning of Earth's crust?

The Sierra Nevada

What mountains block the entire Basin and Range Province causing a rain shadow that is responsible for the arid climate?

Cocos

What plate was NOT involved in the subduction zone that formed the Cascade Mountains?

Elastic Limit

What term is defined as "the point beyond which deformation becomes permanent and is not reversible?"

Normal

What type of fault is shown in the picture?

Tension

What type of stress caused this set of faults?

Normal fault, reverse fault, strike-slip fault

What types of faults are formed by tensional, compressive, and shear stresses, respectively?

Fault gouge and fault breccia

What types of features do geologists look for that provide evidence of faulting?

At the hinge

Where is the term for the region where a fold's limbs intersect?

Syncline

Which of the following geologic structures has the youngest rocks in the middle?

Adjacent Fault

Which of the following is not a type of dip-slip fault?

Volcanic Mountains

Which type of mountains usually form above subduction zones, at divergent boundaries, or at hotspots?

Because a rock must plastically deform around the bend

Why does the formation of a fold require ductile behavior?

Horsts

a block of crust is thrown up between two normal faults

Thrust Fault

a geological fault in which the upper side appears to have been pushed upward by compression

Ductile deformation

a type of solid-state flow that produces a change in the size and shape of a rock body without fracturing. Occurs at depths where temp. and confining pressures are high

Grabens

areas of land that have dropped down between faults

Tensional Stress (crust stretching)

caused by rocks being pulled in opposite directions

Elastic Strain

deformation that is not permanent, provided the stress is released

Joints

fractures in Earth's crust that display no net displacement between the two sides of the crack

Fold-and-thrust Mountains

mountain that develops at a continental collision site along a convergent margin due to orogenisis

Mountain Range

several closely spaced mountains with a common origin

Mountain Belt

several mountain ranges, usually with related histories

Compression Stress (crust shortening)

squeezes rocks together till it folds or break

Left Lateral Strike-Slip Fault

strike-slip fault in which opposite block moves left

Right Lateral Stike-Slip Fault

strike-slip fault in which opposite block moves right

Hooke's Law

the distance of stretch or squeeze of an elastic material is directly proportional to the applied force

The Taconic Orogeny

the first important tectonic activity in the Appalachians, took place during the Ordovician Period. Thrusting and folding occurred mainly in the northern portion of the mountain belt. Uplifted mountains shed sediment to the west, forming the Queenston clastic wedge near Albany, New York.

The Alleghenian Orogeny

the major mountain-building phase responsible for forming the southern Appalachians. It ended during the Pennsylvanian Period. A clastic sedimentary wedge spread over western Pennsylvania, West Virginia, Kentucky, and Tennessee.

The Acadian Orogeny

the major orogeny of the northern Appalachians. It occurred in the Devonian Period and was centered in New England. Sediments accumulated in the Catskill clastic wedge across southern New York and northern Pennsylvania.

Structural Geology

the study of structures that form during tectonic processes and about how such structures form