Chapter 10: Deep Time/Relative Age Dating

Question 1

Erosion

Answer 1

gradual destruction of soils and rock by water, wind, ice, and gravity

Question 2

stratigraphy

Answer 2

the branch of geology concerned with the order and relative position of strata and their relationship to the geological time scale

Question 3

types of sedimentary basins

Answer 3

• foreland basins
• rift basins
• intracontinental basins
• passive margin basins

Question 4

principles of deposition of sediment

Answer 4

• law of superposition

- law of horizontality

Question 5

foreland basin

Answer 5

weight of the mountain belt pushes down the crusts surface

Question 6

rift basins

Answer 6

downward slip on faults produces narrow troughs

Question 7

intracontinental basin

Answer 7

forms in the interior of a continent, perhaps over an old rift

Question 8

passive-margin basin

Answer 8

a beach; where theres not a plate boundary, sediment is deposited because the crust thins out at that area (oceanic crust is thinner than continental crust)

Question 9

stratigraphic formation

Answer 9

A recognizable layer of a specific sedimentary rock type or set of rock types

• deposited during a certain time interval
• can be traced over a broad region

Question 10

superposition

Answer 10

in a sequence of undisturbed layered rocks, the oldest rocks are on the bottom

Question 11

original horizontality

Answer 11

layered rocks are deposited horizontally or close to it

Question 12

cross-cutting relationships

Answer 12

a fault or rock that truncates (intrudes) another rock unit/layer is younger than the rock it cuts into

Question 13

strata continuity

Answer 13

• we can assume that layers are laterally continuous until they thin out to nothing
• erosion can disrupt continuity

Question 14

exceptions to horizontality

Answer 14

preserved dunes: cross beds

Question 15

what causes displacement?

Answer 15

Four types of faulting

• normal
• strike-slip
• reverse
• thrust

Question 16

what causes deformation?

Answer 16

Folding

• changing shape: squishing, like squishing an eraser to a permanent position
• changing orientation; bending

Question 17

unconformity

Answer 17

a gap in the geologic record; occurs where rocks have been removed by erosion or were never laid down (hiatus in deposition)

Question 18

types of uncomformity

Answer 18

• Noncomformity
• Angular conformity
• disconformity
  
  • paraconformity

Question 19

noncomformity

Answer 19

strata on igneous or metamorphic rock (on non-seditmentary rock)

• when erosion occurs the igneous/meta rock will poke up
• occurs with new aqueous invasion (water reappears in this area)

Question 20

angular unconformity

Answer 20

tilted and eroded sedimentary rock under horizontal bedding (T shape)
- vertical (or tilted up) beds capped by horizontal beds

Question 21

disconformity

Answer 21

parallel bedding with erosion

- you can see where part of a layer was eroded/filled in by a younger layer

Question 22

paraconformity

Answer 22

normal parallel bedding, no obvious signs of erosion, need absolute age control to tell that there is discontinuity

Question 23

uniformitarianism

Answer 23

the idea that geologic processes active today are the same as in the past

• “the present in the key to the past”
• demystifying how the Earth works; belief that earth could be understood rationally, without supernatural forces
• use rates and process we observe today to apply over geologic time

Question 24

catastrophism

Answer 24

the idea that extraordinary geologic features require extra-ordinary - perhaps supernatural - explanations
Present day examples include: 2022 Tonga eruption, 2004 Sumatra Earthquake and tsunami
- requires imagination