GENERAL GEOLOGY (CRUSTAL DEFORMATION) Flashcards
A general term that refers to the changes in the shape or position of a rock body in response to DIFFERENTIAL STRESS
Deformation
The forces that deform rocks
Stress
Stress applied uniformly in all direction
Confining pressure
Stress applied unevenly
Differential Stress
Different types of Differential stress
Compressive
Change in shape caused by stress
Strain
Stress: Force = Strain :
Resulting Deformation (Distortion) or change in the shape of rock body
Three types of Deformation
Elastic
Temp and Deformation relations
Higher the temperature (below Earth’s Surfcae) the more ductile defromation
The Lower the temp (at or near surface) Rocks are brittle and tends to fracture
Confininig Pressure Effects on Rocks
The more the pressure the more rocks becomes stronger and harder to break since it is being squeezed and tend to BEND rather than Fracture
Weakest naturally Occuring solid to exhibit Ductile Flow
Glacial Ice
What type of deformation is exhibited by Strong Rocks such as Igneous and Met qtz-rich rocks
Brittle
Type of deformation exhibited by weak sed rocks that contain zone of weaknesses such as foliations
Ductile
Strong Rocks:Brittle = Weak Rocks
Ductile
Why is there salt diapirs
Because of the ductile flow of rock salt
Tectonic Forces Slowly Applied: Ductile = ________ : Fracture
Tectonic Forces Swiftly Applied
Series of Wave Like Undulations of Rocks
Folds
Type of Differential Stress that creates folds
Compressional
Imaginary axis where each layer is bent during folding
Hinge line or hinge
A surface that connects all hinge lines
Axial Plane
parts separated by axial plane
limbs
Arise by upfolding or arching of sed layers
Antiform
Arise by upfolding of sed layers in which the oldest strata are found in the center
Anticline
Downfolds or troughs of sed layes
Synform
Synform with the youngest layer at the center
Synclines
Types of Folds
Symmetrical
When the hinge line tens to slope downwards it is said to be
Plunging Fold
Broad upwarping in basement rocks that deform the overlying cover of sed strata and generate large folds known as
Domes
Why type of igneous intrusion usually form structural domes
Laccoliths
These are economically important rocks structures because when salt migrate upward, the surrounding oil-bearing sed strata deforms to form oil reservoir
Salt Domes
Downwarped structures having gentle sloping beds similar to saucer bowl which are create by gian meteorite impacts
Structural basins
Large STEP LIKE (literally parang baitang sa hagdan) folds in other wise known horizontal Strata which appear to have resulted from reactivation of ancient STEEP DIPPING REVERSE FAULTS located in the basement (Pag nagfulating sa baba susunod ung sediments sa taas)
Monoclines
Brittle Deformation which leads to fracturing and displacement of Earth’s Crust
Faults
faults in which movement is primary dipping or incline to the fault surface
Dip-Slip
Rock surface immediately above the fault
Hanging Wall Block
The Rock Surface immediately below the fault
Footwall Block
Long Low Cliffs created along dip slip faults due the vertical displacement
Fault Scarps
Types of Faults
Normal Fauts
Uplifted fault blocks which forms the ranges in a fault block mountains and the source of sediments in the basins formed by grabens
Horst (hill)
Downdropped fault blocks which constitute the basins
Graben (Ditch)
Fault blocks that have tilted downward but not totally down dropped
Half-Graben
A nearly horizontal fault formd When the slopes of large a series normal faults decreases with depth and eventually join together (MAMA FAULT) which also represent a major boundary between rocks with ductile deformaton and rocks with brittle deformation
Detachment Fault
Earthquake w/c led to the discovery of strike slip faults
1906 San Francisco Equake
When the opposite side of the fault moves to the right when you are facing it
Right Lateral Strike Slip
Example of Dextral Fault
San Andreas
Examples of Sinistral Fault
Ph Fault and Great Glen Fault, Scotland
Major Strike slip faults which slice through the earth’s crust and accomodate motion between two tectoic faults
Transform Faults
Example of Major Transform Faults
1) San Andreas, California
2) Alpine Fault, NZ
3) Dead Sea Fault, Midle East
4) North Anatolian fault, Turkey
These formations usually mark large strike slip faults
1) SAG PONDS
2) LINEAR VALLEYS
Fractues along which no appreciable displacement has occurred
Joints
Formed when igneous rocks cools and develop shrinkage fractures that produce elongated pillarlike colums
Columnar Joints
Process which creates curved joints that is nearly parallel to the surface of large exposed igneous bodies such as batholits and results from gradual expansion that occrus when erosion removes the overlying load
Sheeting
