geolical time

Question 1

what is relative dating?

Answer 1

put things in order without knowing the exact order

Question 2

what are the stratigraphic principals?

Answer 2

principle of superposition
principle of original horizontality
principle of original lateral continuity
principle of cross cutting relationships
principle of inclusion
principle of unconformity
principle of faunal succession (evolution)

Question 3

what is the principle of superposition

Answer 3

because of gravity, oldest sediments are on the bottom

Question 4

what is principle original horizontality

Answer 4

sediment has been deposited in horizontal layers can be deformed into folds or broken by faults

Question 5

what is principle of original lateral continuity?

Answer 5

you can trace undeformed layers from one rock outcrop to another even when some of the layers have been eroded

Question 6

what is the principle of cross cutting relationships?

Answer 6

a geologic feature that cuts across another is younger than the feature it cute across

Question 7

what is the principle of inclusion?

Answer 7

a rock inclusion is older than its host

Question 8

what is the principle of unconformity?

Answer 8

rocks above an unconformity are younger than the rocks below

Question 9

what is an unconformity?

Answer 9

an erosional surface where time is missing from the rock record

Question 10

what is the principle of faunal succession?

Answer 10

an extinct organism will only be found in rocks formed when the organism was alive, therefore fossils appear in a predictable order

Question 11

what is absolute dating?

Answer 11

calculating a numerical date

Question 12

what does number of protons determine?

Answer 12

what element something is

Question 13

what is an isotope?

Answer 13

atoms with different number of neutrons but the same number of protons

Question 14

what is a stable isotope?

Answer 14

dont spontaneously break down

Question 15

what is a radioactive isotope?

Answer 15

breakdown into daughter isotopes over time

Question 16

what is the rate of decay?

Answer 16

how quickly something breaks down

Question 17

how is rate of decay measured?

Answer 17

by half-life, the amount of time it takes for half the sample to break down

Question 18

what is radiometric dating?

Answer 18

calculate the age of a sample (must know half-life and parent to daughter ratio)

Question 19

what happens if an isotope decays too fast?

Answer 19

no parent left, cant keep track of time

Question 20

what happens if an isotope decays too slow?

Answer 20

not enough daughter present to measure reliably

Question 21

what does radiometric dating of igneous rocks measure?

Answer 21

the age of crystallization

Question 22

what does radiometric dating of metamorphic rock meausrre?

Answer 22

age of metamorphism

Question 23

what does radiometric dating of sedimentary rock measure?

Answer 23

the age of formation of crystals in the rock not the rock itself

Question 24

what is the geologic time scale?

Answer 24

a summary of earths history

Question 25

how is geologic time split?

Answer 25

into large units of time called eons

Question 26

how are eons split?

Answer 26

eras, periods, epochs

Question 27

how are the boundaries of units defined?

Answer 27

by the appearance or extinction of an animal or groups of animals

Question 28

how are the absolute ages determined?

Answer 28

through radiometric dating

Question 29

what happens the farther back you go in time?

Answer 29

the more different animals will look until there are no animals at all

Question 30

why dont we know more about earths history?

Answer 30

subduction recycles rocks so they are rare
evidence has been destroyed