Chapter 10

Question 1

Cambrian explosion

Answer 1

The remarkable diversification of life, indicated by the fossil record, that occurred at the beginning of the period of the same name

Question 2

Carbon dating

Answer 2

A radiometric dating process that can tell us the age of organic material containing carbon originally extracted from the atmosphere

Question 3

Contact

Answer 3

The boundary surface between two rock bodies (as between two stratigraphic formations, between an igneous intrusion and adjacent rock, between two igneous rock bodies, or between rocks juxtaposed by a fault)

Question 4

correlation

Answer 4

The process of defining the age relations between the strata at one locality and the strata at another locality (even across seas!)

Question 5

cross-cutting relations

Answer 5

A means of determining the relative age of rock by looking at which rock or structure cuts another. the feature that has been cut is older

Question 6

daughter isotope

Answer 6

The product isotopes of radioactive decay

Question 7

eon

Answer 7

The largest subdivision of geologic time, breaks all time into 4 parts

Question 8

Epoch

Answer 8

An interval of geologic time representing the largest subdivision of a period

Question 9

era

Answer 9

An interval of geologic time representing the largest subdivision of the Phanerozoic Eon (only this Eon is subdivided, and it is divided into 3)

Question 10

fossil succession

Answer 10

The principle that the assemblage of fossil species in a given sequence of sedimentary strata differs from that found in older sequences or in younger sequences. a given species appears at a certain level and then disappears (goes extinct) at a higher level

Question 11

4.57 billion years old

Answer 11

The age of the earth according to isotopic dating.

Question 12

Name two alternative methods for geological dating.

Answer 12

Counting tree rings or seasonal layers in glaciers.

Question 13

Disconformity

Answer 13

layers of sediment accumulate, sea level drops and an erosion surface forms, sea level rises and new sedimentary layers accumulate (looks like the tilt of a beach in diagrams

Question 14

Angular Unconformity

Answer 14

This type of UNCONFORMITY has rock layers that are tilted, and younger sediment layers are deposited horizontally on top of the eroded and tilted layers.

Question 15

Non-Conformity

Answer 15

Igneous or metamorphic rock that has been eroded and included in the rock above

Question 16

marker bed

Answer 16

An easily identified geologic layer whose age has been independently confirmed at numerous locations and whose presence can therefore be used to date archaeological and geological sediments.

Question 17

index fossil

Answer 17

a fossil known to have lived in a particular geologic age that can be used to date the rock layer in which it is found

Question 18

geologic column

Answer 18

an ideal sequence of rock layers that contains all the known fossils and rock formations on Earth arranged from oldest to youngest, may also be composed for a single region

Question 19

geologic map

Answer 19

Shows the surface geology of the mapped Includes rock types, their ages, and location of faults

Question 20

geologic time

Answer 20

A record of the geologic events and life forms in Earth’s history, divided into 4 eons OR 4 eras, includes scale

Question 21

half-life

Answer 21

The time it takes for half of a group of a radioactive element’s isotopes to decay

Question 22

isotope

Answer 22

Different versions of a given element that have the same atomic number but different atomic weights, aka have more or less neutrons

Question 23

isotopic dating

Answer 23

The science of dating geologic events in years by measuring the ratio of parent radioactive isotopes to daughter product isotopes

Question 24

numerical age

Answer 24

The age of a rock or structure as specified in years. referred to as ‘absolute age’ in older literature. Absolute was abandoned because in reality, this is still a guess. May be done through radiometric, carbon, or isotopic dating (all the same idea).

Question 25

original horizontality

Answer 25

The principle that sediments are deposited in nearly horizontal layers (1st principle of relative dating)

Question 26

parent isotope

Answer 26

A radioactive isotope that undergoes decay

Question 27

geochronology

Answer 27

study of the ages of geologic events

Question 28

fossil assemblage

Answer 28

a group of fossil species found in a specific sequence of sedimentary rock

Question 29

closure temperature

Answer 29

One of the problems with radiometric dating, radioactive material must reach a certain temperature before it begins to “set it’s timer”. Hence, no rocks date back to the Hadean eon (never reached this temp).

Question 30

uniformitarianism

Answer 30

The principle that the same physical processes observed today are responsible for the formation of ancient geologic features. put concisely, ‘the present is the key to the past’. Hutton.

Question 31

unconformity

Answer 31

A boundary between two different rock sequences representing an interval of time during which new strata were not deposited and/or were eroded

Question 32

superposition

Answer 32

The principle that younger layers of sediment are deposited on older layers of sediment. thus, in a sequence of strata, the oldest layer is at the base

Question 33

stratigraphic formation

Answer 33

A recognizable layer of a specific sedimentary rock type or set of rock types, deposited during a certain time interval, that can be traced over a broad region. Places two now separate land masses as being connected at a certain time.

Question 34

stratigraphic column

Answer 34

A cross-section diagram of a sequence of strata summarizing information about the sequence in a given region

Question 35

relative age

Answer 35

The age of one geologic feature with respect to another, eg feature A is older than feature B

Question 36

period

Answer 36

An interval of geologic time representing a subdivision of a geologic era–these names were given at different times and are not all the same length and do not follow a pattern for their names.

Question 37

Precambrian

Answer 37

The interval of geologic time (known as an era, divided into 3 eons) between Earth’s formation about 4.57 Ga and the beginning of the Phanerozoic Eon 542 Ma

Question 38

radioactive decay

Answer 38

The process by which a radioactive atom undergoes fission aka releases particles thereby transforming into a new element