glacial dating- visualizing in 3D

Question 1

Why do rocks fold and fault?

Answer 1

• when rocks are subjected to stress and undergo strain they fold and fault
• there are different kinds oof stress including compressional, tensoinal, and shear

Question 2

How do rocks respond to stress?

Answer 2

• rocks respond in two ways:
• Elastic strain: deformed body recovers when stress is removed. Think elastic band. When the stress is beyond the elastic limit, permanent deformation is caused
• Plastic strain: bends but does not return to original shape. Rocks under increased temperature/pressure. For example, rocks in the mantle. Ex. glacial ice, asthenosphere
• brittle

Question 3

*How do rocks fold?

Answer 3

• folds or bends in layered rocks. caused by plastic strain
• depending on the stress, strain behaviour on the rock changes. Folds can become permanent after strain is removed: this can casued a fault
• types of folds: anticline, syncline, overturned, recumbent

Question 4

What are fractures and faults?

Answer 4

joints- rocks fractures, no displacement (not a fault)
faults- fractures along which movements has taken place. An active fault is classified as having movement within 11000 years
- Types of faults: normal, reverse, thrust, strike slip

Question 5

How does fault formation reflect the type of stress to which rocks are subjected?*****

Answer 5

• different types of faults are caused by different types of stress

Question 6

anticline

Answer 6

• upward arching fold
• synclines and anticlines often occur together

Question 7

syncline

Answer 7

• downward arching fold
• synclines and anticlines often occur together

Question 8

overturned fold

Answer 8

anticline goes over syncline due to lots of folding

Question 9

recumbent fold

Answer 9

• axial plane is at the axsis of orientation. straight lines in the horizion
• axial plane is essentially horizontal,

Question 10

compressional stress

Answer 10

• forces pushing together
• convergent boundaries have compressional stress
• ex. convergent plate margins

Question 11

tensional stress

Answer 11

• forces pulling apart
• ex. divergent plant margins

Question 12

shear stress

Answer 12

• parallel; opposing forces
• ex. transform plate margins

Question 13

normal fault

Answer 13

• hanging wall block moves downward relative to footwall block
• caused by tensional stress
• can produce a graben or horst
• ex. East african rift valley, or just a rift valley in general

Question 14

reverse fault

Answer 14

• hanging wall block moves upwards relative to footwall block
• causes by compressional stress
• often caused by compressional stress

Question 15

thrust fault

Answer 15

• reverse fault with very low angle fault (less than 45 degrees)
• causes by compressional stress

Question 16

strike slip fault

Answer 16

• a fault where the movement is predominantly horizontal and therefore parallel to the strike of the fault
• causes by shear stress
• found in transform boundaries

Question 17

hanging wall block

Answer 17

• overlies an inclined fault plane

Question 18

footwall block

Answer 18

• underlies an incline fault plane

Question 19

strain

Answer 19

change in size/shape in response to stress

Question 20

folds

Answer 20

• bends in layered rock due to plastic strain

Question 21

hinge line

Answer 21

axis of the fold

Question 22

axial plane

Answer 22

plane contaiing all hinge lines of a fold

Question 23

where do we find water/gas/oil?

Answer 23

• we can map out where faults may be
• most fossil fuels are found in sedimentary rock
• reasources can be found in a resivor over an anticline trap, oil and gas rise to the crest(top) of the fold
• also found in fault traps which is where oil and gas collect in tilted strata adjacent to the fault
• also salt dome traps and stratigraphic trap
• it takes millions of years for reasoureces to replenish
• it is important because we are buring fossil fuels so quickly that they will not be replenished in our lifetime

Question 24

horst

Answer 24

a block pushed upward relative to the blocks on either side b the faulting

Question 25

graben

Answer 25

a block that has been lowered relative to the blocks on either side due to the faulting

Question 26

brittle

Answer 26

• breaks or fractures, ex. faults
• surface rocks

Question 27

appalacian valley and ridge

Answer 27

• folding at appalacians tells us that appalacians are no longer growing
• it is an old mountain range
• folds are only found at active tctonic plate boundaries
• at the appalacians, it is no lonher active and is eroding away