Metamorphism and Deformation

Question 1

the force applied per unit area

• unit of measurement: N/m squared or Pascal
• can exist without strain

Answer 1

stress

Question 2

change in rocks due to different types of stress; deformation per unit area
- unitless; change in L over L
- cannot exist without stress

Answer 2

strain

Question 3

types of stress

Answer 3

uniform and differential stress

Question 4

the forces that act uniformly/equally from all directions; aka pressure

e.g. confining stress/pressure

Answer 4

uniform stress

Question 5

the weight of overlying rocks that
exert pressure

Answer 5

confining pressure

Question 6

stress where the forces are not equal
from all directions

Answer 6

differential stress

Question 7

types of differential stress and its effect

Answer 7

tensional, compressional, and shear stress

• rocks get deformed

Question 8

this differential stress happens when pieces of rock are pulled apart.

• produces normal fault

Answer 8

tensional stress

Question 9

occurs when two blocks of rock move toward and push against one another

• produces a reverse fault

Answer 9

compressional stress

Question 10

when slabs of rock slide past each other horizontally in opposite directions. The rocks are not smashed into each other or pulled apart, but their edges slide along each other with a lot of friction.

• produces a strike-slip fault

Answer 10

shearing stress

Question 11

stages of deformation

Answer 11

1. elastic deformation stage
2. ductile deformation stage
3. fracture stage

Question 12

stage of deformation where the strain is reversible

Answer 12

elastic deformation stage

Question 13

stage of deformation where the strain is irreversible/permanent; without breaking

Answer 13

ductile deformation stage

Question 14

stage of deformation where the strain is irreversible/ permanent; rocks break

Answer 14

fracture stage

Question 15

a material that does not return to its original shape after it is deformed

e.g. rocks

Answer 15

inelastic

Question 16

type/behavior of materials
- affects deformation

Answer 16

brittle and ductile

Question 17

materials that have a small or large region of elastic behavior but only a small region of ductile behavior before they fracture

Answer 17

brittle materials

Question 18

materials that have a small region of elastic behavior and a large region of ductile behavior before they fracture

Answer 18

ductile materials

Question 19

factors that affect the behavior of the material

Answer 19

temperature, confining pressure, strain rate, type of materials/composition

Question 20

• at high temperature, molecules and their bonds can stretch and move, thus materials will behave in a more _____ manner
• at low temp, materials are _________

Answer 20

ductile, brittle

Question 21

• at high confining pressure, materials are less likely to fracture (__________)
• at low, the material will be ______ and tend to fracture sooner

Answer 21

ductile, brittle

Question 22

• at high strain rates, materials tend to fracture (___________)
• at low, more time is available for individual atoms to move, thus _______ behavior is favored

Answer 22

brittle, ductile

Question 23

quartz and olivine behavior

Answer 23

brittle

Question 24

clay minerals such as calcite behavior

Answer 24

ductile

Question 25

water appears to weaken the chemical bonds and forms films around mineral grains wet rock - ____________ dry rock - ______________

Answer 25

ductile, brittle

Question 26

effects of deformation

Answer 26

joints, folds, faults, metamorphism

Question 27

natural cracks on the surface produced by brittle deformation due to tensional stress

Answer 27

joints

Question 28

contortion of rock layers forming wave-like curves due to ductile deformation caused by compressional stress

Answer 28

folds

Question 29

- planar fracture on rocks caused by differential stress

Answer 29

faults

Question 30

the process that occurs when rocks change their form into a new one without undergoing melting or disintegration * size, shape, and arrangement of grains in the rocks may change (physical) or new minerals may grow (chemical)

Answer 30

metamorphism

Question 31

original rock of metamorphism

Answer 31

protolith

Question 32

factors of metamorphism

Answer 32

temperature, pressure chemically-active fluids, parent rock

Question 33

why shouldn't the rock melt or disintegrate during metamorphism

Answer 33

because it will become magma

Question 34

endogenic metamorphism

Answer 34

regional, contact, hydrothermal, cataclastic/dynamic

Question 35

exogenic x endogenic metamorphism

Answer 35

burial

Question 36

exogenic/extraterrestrial metamorphism

Answer 36

shock

Question 37

occurs due to pressure and heat applied to rocks by converging plates and mountain building - produce a large volume of metamorphic rocks - high pressure and temperature but low water

Answer 37

regional metamorphism

Question 38

occurs due to heating (“baking”) of country rocks by rising magma (magma intrusion) - high temperature, no added pressure; fluids may be present from groundwater reservoir or seafloor - examples: marble, quartzite, and hornfels

Answer 38

contact metamorphism

Question 39

driven by hot fluid, commonly water - addition of fluids promotes recrystallization (change in size and shape of minerals, physical) and neocrystallization (formation of new minerals by chemical reaction with fluids) - occurs in oceanic ridges (diverging plates), subduction zone (converging plates), and groundwater near magma chamber - Example: serpentine; blueschist

Answer 39

hydrothermal metamorphism

Question 40

due to the shearing of plastic-like rocks near the fault line; example: mylonite

Answer 40

cataclastic/dynamic

Question 41

due to the confining pressure of overlying rocks and the increasing temperature and pressures at the deeper portion of the crust; example: metaconglomerate

Answer 41

burial

Question 42

due to the pressure brought by the impact of extraterrestrial objects (i.e. meteorites); metamorphic rocks formed are called impactite

Answer 42

shock

Question 43

two types of metamorphic rocks

Answer 43

foliated and non-foliated

Question 44

type of metamorphic rock Minerals are aligned in parallel layers and form bands - Rocks commonly form flakes when they break

Answer 44

foliated

Question 44

type of metamorphic rock Minerals are aligned in parallel layers and form bands - Rocks commonly form flakes when they break

Answer 44

foliated

Question 45

type of metamorphic rock Minerals are randomly oriented and usually have granular appearance - Rocks do not flake in thin layers when they break

Answer 45

non-foliated

Question 46

with increasing temp and pressure, metamorphic grade also _____________. the higher the metamorphic grade, the more _____ the rock will be from its original form

Answer 46

increases, changed