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7 - Geological Structures
rocks.
15
Geology
Undergraduate 1
05/31/2011

Additional Geology Flashcards

 


 

Cards

Term
Stress
Definition
Refers to the force

Measured in force per unit area
Term
Types of Stress and Strain
Definition
Compression, Tension, Shear (Stress)

Compresisonal, Tensional, Shear (Strain)
Term
Strain
Definition
Refers to the deformation

The amount of deformation an object experienced compared to its original state
Term
Types of Deformation
Definition
Brittle Deformation (Permanent)
Elastic Deformation (Non-permanent)
Plastic Deformation (Permanent)
Term
Brittle Deformation
Definition
(Permanent)
Breaks/fractures like a rigid body
Rocks are typically brittle at low pressures/temperatures
Term
Elastic Deformation
Definition
(Non-permanent)
Object deforms, but then returns to its original size and shape when the stress is released
Rubber band
Typically negligible in rocks
Term
Plastic Deformation (Permanent)
Definition
(Permanent)
Object deforms, does not break, and undergoes non-reversible shape changes
Paper clip
Rocks deform plastically at high pressures/temperatures
Term
Controlling Factors on Plastic versus Brittle Fracture Deformation
Definition
Temperature (High Temp = Plastic)
Confining Pressure
Strain Rate (High Strain Rate = Brittle)
Lithology (Rock types affect brittle/plastic)
Time
Term
When will permanent deformation of rock occur?
Definition
When the applied stress exceeds the strength of the rock.
Term
When will nonpermanent (elastic) deformation occur?
Definition
When weak stresses are applied. In such cases stress and strain are proportional. When the stress is reduced or removed the rock will return to its original form.
Term
Isostatic Rebound
Definition
- The elastic response of the lithosphere following the removal of a large stress. (Continental glaciers, mountains, etc)
- Example of Elastic Deformation in geology
- Large mass deforms the crust elastically, when it is removed the crust bounces back to its original shape over thousands of years (about 1/10 of an inch/year)
Term
Glacial Isostacy
Definition
Isostatic rebound of the earth after glaciers receded.
Term
[image]
Definition

 

The northern Great Lakes area is isostatically rebounding 5 mm per year.  Eventually the Great Lakes will be drained via the Mississippi River system.

Term
[image]
Definition

 

Anticlines and synclines are symmetric folds that form from bi-directional compressive stress.  The anticline on the right is plunging into the slide.

Term
[image]
Definition

 

As anticlines and synclines erode note the outcrop pattern in the center of the eroding fold.  Which fold will expose the oldest rock in the center (near its axis) as it erodes.  Note the difference in outcrop pattern of the plunging anticline versus the non-plunging folds on the left of the slide.

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