Chap 8

Question 1

Relative age

Answer 1

The sequence in which events took place

Question 2

Numerical age

Answer 2

the age of events or objects expressed as a number of numbers
Determined using radiometric dating
Also known as absolute age

Question 3

Contacts

Answer 3

Surfaces seperating successive rock and layers

Question 4

Formations

Answer 4

Bodies of rock of considerable thickness with recognizeable characteristics allowing them to be distinguished from adjacent rock layers

Question 5

Principle of original horizontality

Answer 5

Beds of sediment deposited in water formed as horizontal or nearly horizontal layers

Question 6

Principle of superposition

Answer 6

within sequence of undisturbed sedimentary or volcanic rocks the layers get younger from bottom to top

Question 7

Principle of lateral continuity

Answer 7

an orignal sedimentary layer extends laterally until it tapers or thins at its edges

Question 8

Principle of cross cutting relationships

Answer 8

disrupted pattern is older than the cause of disruption

Question 9

principle of inclusions

Answer 9

fragments embedded in host rock are older than the host rock

Question 10

Baked contacts

Answer 10

contacts between igneous intrusions and surrounding rocks where surrounding rocks have experienced contact metamorphism

Question 11

Principle of faunal succession

Answer 11

Fossils appear and disappear in strata in definite and recognizable order due to evolution

Question 12

Unconformity

Answer 12

A surface or contact that represents a break in the geologic record

1: angular unconformities
2: Disconformities
3: Nonconformities

Question 13

Angular Unformity

Answer 13

A contact in which younger strata overlies an erosion surface on tilted or golded layered rock

Question 14

Nonconformity

Answer 14

an unconformity in which an erosional surace on plutonic or metamorphic rock has been covered by younger sedimentary or volcanic rock

Question 15

Correlation

Answer 15

determining time equivvalency of rock unites to determine younger or older than another area

1: Lithologic correlation
2: Time correlation (eg index fossil, key bed, unconformities)

Question 16

Physical continuity

Answer 16

Physically trace continues exposure of a rock unit

Question 17

Key bed

Answer 17

A very distinct layer, can be used to correlate rocks over great distance E.g. volcanic ash layer

Question 18

Index fossil

Answer 18

Very shortlived wide spread species known to exist during a specific period of geologic time

Question 19

Faunal succession

Answer 19

fossil species succeed in one another through the layers in a predictable order

Question 20

The standard geological time scale

Answer 20

Precambrian - 87% of geologic time
Paleozoic era - Old life, appearance of complex life
Mesozoic era - middle life, dinos abundant,
cenozoic era - new life, mammals and birds abundant

Question 21

radioactive decay

Answer 21

the spontaneous nuclear change of isotopes with unstable nuclei

Question 22

Half life

Answer 22

the time it takes for a given amount of a radio active isotope to be reduced by half