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