Diastrophism
Fracture
irreversible strain wherein the material breaks.
strain
is a change in size, shape, or volume of a material.
Fold Axis
is a line connecting all points on the hinge.
Thrust fault
is a special case of a reverse fault where the dip of the fault is less than 15 deg.
Uniform Stress
is a stress wherein all the forces act equally from all directions
Stress
is force applied per unit area
Olivine
is stronger than the minerals that make up most crustal rocks, so the upper part of the mantle is again strong.
dip
is the angle between a horizontal plane and the inclined plane, measured perpendicular to the direction of strike.
strike
is the compass direction of any horizontal line on the plane
Diastrophism
is the large-scale deformation of the Earth's crust by natural processes. It leads to the formation of continents and ocean basins, mountain systems, plateaus, rift valleys, and other features. The deformations are caused by mechanisms such as lithospheric plate movement (plate tectonics), volcanic loading, or folding.
Hinge
is where limbs intersect; it the tightest part of the fold.
Differential Stress
occurs when stress acting on the rock is not equal in all directions
Fault Block Mountains
originate by faulting.
The Sierra Nevada mountains of California
resulted from both normal and reverse faults.
'iso'
same
plunge
the angle that the fold axis makes with a horizontal line
hanging wall block
the block above the fault
footwall block.
the block below the fault
horsts
uplifted blocks
Ductile Deformation
wherein the strain is irreversible.
Elastic Deformation
wherein the strain is reversible.
Fold & Thrust Mountains
Large compressional stresses can be generated in the crust by tectonic forces that cause continental crustal areas to collide
Examples of Volcanic mountains
The Cascade Mountains of the western U.S and the mountains of the Hawaiian Islands and Iceland
Faults
fracture of rock with displacement
Joints
fracture of rock without displacement. They affect the resistance of the rock to erosion by weakening the rock and making it susceptible to weathering.
Brittle materials
have a small or large region of elastic behavior but only a small region of ductile behavior before they fracture.
Ductile materials
have a small region of elastic behavior and a large region of ductile behavior before they fracture.
chevron fold
A fold that has no curvature in its hinge and straight-sided limbs that form a zigzag pattern
Half-Grabens
A normal fault that has a curved fault plane with the dip decreasing with depth can cause the down-dropped block to rotate
axial plane
An imaginary plane that includes the fold axis and divides the fold as symmetrically as possible
recumbant fold
An overturned fold with an axial plane that is nearly horizontal
Confining Pressure
At high confining pressure materials are less likely to fracture because the pressure of the surroundings tends to hinder the formation of fractures. At low confining stress, material will be brittle and tend to fracture sooner.
Strain Rate/Time
At high strain rates material tends to fracture. At low strain rates more time is available for individual atoms to move and therefore ductile behavior is favored.
Temperature
At high temperature molecules and their bonds can stretch and move, thus materials will behave in more ductile manner. At low temperatures, materials are brittle.
Dip Slip Faults
are faults that have an inclined fault plane and along which the relative displacement or offset has occurred along the dip direction.
Reverse Faults
are faults that result from horizontal compressional stresses in brittle rocks, where the hanging-wall block has moved up relative the footwall block.
Normal Faults
are faults that result from horizontal tensional stresses in brittle rocks and where the hanging-wall block has moved down relative to the footwall block.
Strike Slip Faults
are faults where the relative motion on the fault has taken place along a horizontal direction.
Anticlines
are folds where the originally horizontal strata has been folded upward, and the two limbs of the fold dip away from the hinge of the fold.
Synclines
are folds where the originally horizontal strata have been folded downward, and the two limbs of the fold dip inward toward the hinge of the fold.
Volcanic Mountains
are not formed by deformational processes, but instead by the outpouring of magma onto the surface of the Earth.
Slickensides
are scratch marks that are left on the fault plane as one block moves relative to the other.
Limbs
are sides of a fold.
Monoclines
are the simplest types of folds. They occur when horizontal strata are bent upward so that the two limbs of the fold are still horizontal.
Folds
bending of rock without breaking (including tilting).
Factors Affecting the Kind of Deformation
- Confining Pressure - Temperature - Strength of Rock/Composition - Strain Rate/Time
Stages of Deformation
- Elastic Deformation - Ductile Deformation - Fracture
Types of Deformation When Rocks are Subjected to Stress
- Faults - Folds - Joints
two varieties of Strike slip faults
- Left-lateral strike-slip fault - Right-lateral strike-slip fault
Three Kinds of Differential Stress
- Tensional Stress - Compressional Stress - Shear Stress
three types of mountains
-Fault Block Mountains -Fold & Thrust Mountains -Volcanic Mountains
Geometry of Folds
-Limbs -Hinge -Fold Axis
The Himalayan Mountains
-currently the highest mountain on Earth. - formed as a result of the Indian Plate colliding with the Eurasian plate.
Evidence of Movement on Faults
-slikensides -fault breccias
ductile
Deeper than this point rock strength decreases because fractures become closed and the temperature is higher, making the rocks behave in a ____manner.
Horsts & Grabens
Due to the tensional stress responsible for normal faults, they often occur in a series, with adjacent faults dipping in opposite directions.
left-lateral strike-slip fault
If the block on the other side has moved to the left
right-lateral strike-slip fault
If the block on the other side has moved to the right
isoclinal fold
If the compressional stresses that cause the folding are intense, the fold can close up and have limbs that are parallel to each other
plunging fold
If the fold axis is not horizontal
overturned fold
If the folding is so intense that the strata on one limb of the fold becomes nearly upside down
asymmetrical fold
If the limbs dip at different angles
symmetrical fold
If the two limbs of the fold dip away from the axis with the same angle
Strength of Rock/Composition
Minerals like quartz, and feldspars are very brittle. Calcite, clay minerals, and micas are more ductile. This is due to the chemical bond types that hold them together. Another aspect is presence or absence of water. Wet rock tends to behave in ductile manner, while dry rocks tend to be brittle.
brittle
Rocks near the surface of the Earth behave in a ____ manner
brittle-ductile transition zone
a point located at a depth of about 15 km
Pressure
a type of uniform stress
Confining Stress
a uniform stress/pressure exerted by the weight of overlying rocks.
'cline'
angle
Transform faults
are a special class of strike-slip faults. These are plate boundaries along which two plates slide past one another in a horizontal manner.
Crustal rocks
are composed of minerals like quartz and feldspar which have high strength, particularly at low pressure and temperature.
Fault Breccias
are crumbled up rocks consisting of angular fragments that were formed as a result of grinding and crushing movement along a fault.
grabens
down-dropped blocks
Shear Stress
stress which results in slippage and translation
Compressional Stress
stress which squeezes rock
Tensional Stress
stress which stretches rock