Ch9 Flashcards Preview

ESC1000L > Ch9 > Flashcards

Flashcards in Ch9 Deck (17):
1

Relative dating

dating describes age in relation to events or when something formed

2

Absolute dating

determines age in exact units of time; given as a number.
ex- my dog is 3

3

Laws for determining (relative) age

1) Original horizontality
2) Superposition
3) Inclusion
4) Cross Cutting

4

Original Horizontality

most sediments and lava flows are originally deposited in horizontal sheets. There horizontal rock layers are called beds, or strata

5

Superposition

­‐ in any sequences of undeformed sedimentary rocks or lava flows, oldest layers are at bottom of sequence, while youngest layers at top

6

Inclusion

a clast included in another rock must be older than the rock it is in

7

Cross cutting

Any feature that cuts through a body of rock is younger than that rock

8

Unconformity

Gap, deposition without anything fucking it up

9

Angular Unconformity

Consist of tilted or folded sedimentary rocks that are overlain by younger, more flat-lying strata

10

Disconformity

a gap in the rock record that represents a period during which erosion rather than deposition occurred.

11

Nonconformity

consists of younger sedimentary rocks that overlie older metamorphic or igneous rocks

12

Importance of fossils

determine geologic history and prehistoric environments.

13

Principle of fossil succession

states that fossils succeed each other in a definite and determinable order

-can be used to date stratas

14

Range zone

interval in the rock for which a certain fossil is found is called a range zone

15

Radiometric Dating of rocks

Radioactive isotopes - emit particles from their nuclei that cause radiation.Ultimately, the process produces a stable nonradioactive and stable isotope

16

Unstable isotopes

isotope that decays is the parent, while the isotopes it produces are the daughters

17

Rate of Decay

indicated by the half-life, the time it takes for half of the parent isotopes to decay.