Deformed rocks

Question 1

Mountains/Mountain building

Answer 1

Mountain Building
Orogenesis
Uplift
Deformation
Metamorphism
Mountain building events are called “orogenies”
Evidence of tectonism

Mountain belts are (geologically) temporary and ever-changing
Constructive and destructive processes

ask yourself what tectonic process might have made it. Is it active now or was it a long time ago?

Question 2

deformation

Answer 2

rocks deform in response to directional stress

Ductile deformation: (more bendy)
High temperatures
Long periods of time

Brittle deformation (spaghetti noodles we broke)
Low temperatures
Short periods of time

Question 3

brittle deformation

Answer 3

Brittle
Fast
Cold
Stress exceeds the breaking point
Irreversible break

Question 4

ductile deformation

Answer 4

Ductile
Slow
Warm
Stress does NOT exceed the breaking point
Irreversible change in size and/or shape (when pressures are removed it doesn’t snap back)
Volume and density may change

Question 5

undeformed/deformed rocks

Answer 5

Undeformed rocks have horizontal beds, spherical sand grains, no folds and faults, have to have them to have deformed rocks
Deformed rocks show tilted beds, metamorphic alteration, folding and faulting

Question 6

displacement
rotation
distortion

Answer 6

dis: slide down
rotate
distortion: stretch, bend, etc.

Question 7

strain types

Answer 7

Stretching(divergent)
Elongation

Shortening(convergent)
Contraction

Shear(transform)
Opposing forces

Question 8

stress

Answer 8

Strain is the result of deformation

Deformation is caused by force acting on a rock and that force is called stress

Type of stress
Compression
Tension
Shear
Pressure

Question 9

compression

Answer 9

convergent
Material is squeezed
Shortens and thickens
Drives collision and orogenesis
causes most of our mtn building events

Question 10

tension

Answer 10

divergent
Material is pulled apart
Stretches and thins
Drives crustal rifting
causes our mtn range building

Question 11

shear

Answer 11

transform
Surfaces slide past each other
Neither thickens nor thins

Question 12

pressure

Answer 12

Equal stress on all sides
like a diver under water

Question 13

Measuring and communicating the geometry of the geologic structure:

strike and dip

Answer 13

Orientation of imaginary planes
(No, not Wonder Woman’s)
Dip
Angle of inclination downward (steepness of the inclined plane)
(if you spit on it which way would the spit roll)

Strike
Compass direction (such as 95 degrees from North) of a horizontal line (pretend to fill with water which creates a horizontal line, direction is where the line aligns with the inclined plane)
Where the inclined plane intersects an imaginary horizontal plane

helps us understand what caused the deformation

Question 14

structural features: joints

Answer 14

Brittle deformation
No displacement or shear
Usually formed as overburden is removed
Also formed by cooling of igneous rocks
Significance?
Fluid flow, groundwater, oil, ore, weathering into beautiful Bryce Canyon…

Question 15

structural features: veins

Answer 15

Joints allow groundwater flow
Mineral-rich groundwater can deposit veins of minerals in the joints
Example: limestone from Rock Canyon
cracks happened, and those are filled with minerals (ex: dark rocks with white veins)

Question 16

structural features: faults

Answer 16

Brittle
Fractures where displacement has occurred
Two blocks are defined
One on either side of the fault

Question 17

Strike-slip: Right lateral vs Left lateral

Answer 17

Imagine yourself standing looking over the fault to the other side. Which way did the other side move relative to you?

Question 18

fault practice

Answer 18

find hanging wall:
if it moves down: normal
moves up: reverse

Question 19

stustural features: folds

Answer 19

Rock layers are warped due to ductile deformation
Horizontal compression (orogenies)
Can have multiple episodes of folding
Classification
Strike of the hinge line
Dip of the limbs
Anticlines, Synclines, Monoclines, etc

Question 19

anticline

Answer 19

Warp upward
Dips away from middle
Strike is horizontal to ground surface
Makes a frown or an “A”
Oldest layers exposed in the center

Question 19

syncline

Answer 19

Warp downward
Dip toward middle
Strike is horizontal to the ground surface
Makes a smile or a “U”
Youngest layers exposed in the center (bottom is oldest layers)

Question 20

monoclines

Answer 20

Dip only in one direction
Strike is horizontal to ground surface (doesn’t dip below ground)

Question 21

plunging fold

Answer 21

Strike (or fold axis) is dipping or “plunging”
Can be anticlines or synclines or even monoclines
“Plunging anticline” etc.
Sheep Mountain, WY
Virgin Anticline, Hurricane, UT
quail creek resevoire** cool to visit

Question 22

domes and basins

Answer 22

Generally occur in continental interiors
Broadly warped regions
Roughly circular patterns
Domes
Oldest strata in middle (upside down bowl, water runs down to edges away from middle)
Basins
Youngest strata in middle
all comes down in the middle, (water gathers in the middle) multiple pressures in areas farther away from specific pressure points

Question 23

the richat structure (woah beautiful)

Answer 23

Sahara Desert of Mauritania
At first believed to be an impact crater
Now has been mapped as a structural dome
know how to tell which layers are older

Question 24

Mountains– Continental-Continental Convergence

Answer 24

most pervasive or largest mtns in the world

Question 25

Mountains—Divergence

Answer 25

rift margins rise to form mountains
rifts and horsts
mt timp