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