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Earth Science > Geologic Time Scale & Age of Earth > Flashcards

Geologic Time Scale & Age of Earth Flashcards

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1
Q

______ time puts numbers and dates on things

A

absolute

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2
Q

The geologic time scale is a way of ________ the different time periods - and the whole time the earth has been in existence.

A

organizing

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3
Q

The geologic time scale is a visual ________ of geologic time

A

representation

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4
Q

What is the geologic time scale?

A

a visual representation of geologic time

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5
Q

The geologic time scale is based on…

A

the succession of rock layers

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6
Q

The geologic time scale is divided into:

A

Eons-> Eras -> Periods -> Epochs

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7
Q

What is the Precambrian supereon?

A

the period of time on the Earth before there was any life on Earth

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8
Q

About 600 million years ago we began which eon?

A

Phanerozoic

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9
Q

The Phanerozoic eon includes which three eras?

A

Paleozoic, Mesozoic, Cenozoic

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10
Q

The Paleozoic era was marked by…

A

single cell life that developed into mostly ocean-dwelling creatures

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11
Q

The Paleozoic era was marked by ______ cell life that developed into mostly ocean- ______ creatures.

A

single, ocean

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12
Q

The Mesozoic Era was the Age of the…

A

Dinosaurs

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13
Q

The Cenozoic Era has been named the Age of the…

A

Mammals

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14
Q

which eon are we currently in?

A

the Phanerozoic eon

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15
Q

which era are we currently in?

A

the Cenozoic era

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16
Q

What are Eras further divided up into?

A

Periods

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17
Q

how long to periods last?

A

millions of years

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18
Q

The starting and ending dates of most periods are based on…

A

fossil groups

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19
Q

Some period boundaries are marked by ______

A

extinctions.

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20
Q

Periods are further subdivided into…

A

epochs

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21
Q

Some of the earliest attempts at estimating the Age of the Earth are based on…

A

sedimentation, and thickness of the strata

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22
Q

The earliest attempts at estimating the Age of the Earth looked at a series of rock _____ and figuring out how long it might have taken to ______ all of those rock units.

A

units, deposit

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23
Q

To conduct accurate estimations of the age of the earth based on sedimentation you would need to assume that there was…

A

a constant record of deposition and no weathering/erosion

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24
Q

Sir Halley came up with a method to estimate the age of the earth by looking at…

A

the oceans, and how much salt is dissolved in the oceans.

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25
Q

Sir Halleys theory is that if you could assume that the oceans were originally ________, how long would it have taken for them to accumulate the amount of _____ that they have today

A

freshwater, salt

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26
Q

By using Sir Halley’s method what was the estimated age of the earth?

A

90 million years.

27
Q

What were the flaws of Sir Halley’s method?

A
  • you need to assume that the ocean started at 0% salinity (which isn’t necessarily true)
  • you need to assume that the salt content doesn’t vary (which isn’t necessarily true: salt content can be lost through tectonic, biologic processes)
28
Q

How can salt content be lost in the ocean?

A

through biologic, tectonic processes

29
Q

What was Darwin’s estimate of the age of the earth based on?

A

the time it would be necessary toe rod a particular mountain range in Europe

30
Q

How old did Darwin estimate the Earth to be?

A

300 million years old

31
Q

who challenged and rejected Darwin’s theory/method?

A

Lord Kelvin

32
Q

what was Lord Kelvin’s estimate of the Earth based on?

A

thermodynamic cooling

33
Q

Lord Kelvin assumed that the Earth was once completely ______ _____, which is a temperature ranges between ____-____ degrees Celsius

A

molten rock, 800-1200

34
Q

Lord Kelvin assumed that the Earth has been cooling since its original molten rock state, what did he calculate to get an age of the Earth?

A

he calculated how long it would take for the Earth to cool down to its current temperature

35
Q

How old did Lord kelvin estimate the Earth to be?

A

20-100 million years

36
Q

what were the flaws with Lord Kelvin’s thinking?

A
  • He needed to assume that no heat was added to earth after its formation, which was proven to be not true by the discovery of radioactivity by Marie Curie
37
Q

what discovery invalidated Lord Kelvin’s theory?

A

the discovery of radioactivity

38
Q

What is radioactivity?

A

the breakdown of unstable elements that releases energy in the form of heat

39
Q

who discovered radioactivity?

A

Marie Curie

40
Q

Radioactivity is the _______ of unstable elements that releases energy in the form of ______

A

breakdown, heat

41
Q

What do modern estimated base their estimation of earth’s age on?

A

theometric dating

42
Q

What do modern estimated base their estimation of earth’s age on?

A

radiometric dating

43
Q

How old do modern scientists estimate the Earth to be?

A

4.55 billion years

44
Q

Radioactive elements are unstable ______ of an otherwise stable element.

A

isotopes

45
Q

radioactive elements are important to…

A

figuring out the age of geologic materials as well as in environmental questions

46
Q

how any radioactive elements have been discovered?

A

> 1500

47
Q

Radioactive elements are ______

A

unstable

48
Q

Radioactive elements are unstable which means they _____ into stable _____

A

decay, stable

49
Q

Decay occurs at _____ rates for each type of radioactive element

A

different.

50
Q

The rate at which an element decays is known as…

A

an element’s half life

51
Q

a gigabite is ______ bites, a gigayear is _____ years

A

1 billion, 1 billion

52
Q

What is a half life?

A

a measure of how quickly a radioactive element decays

53
Q

A half life is a measure of how quickly a ______ element decays.

A

radioactive

54
Q

A half life is the time needed for half the _____ atoms in a sample to decay

A

parent

55
Q

What are the parent atoms?

A

the unstable radioactive atoms

56
Q

What are the daughter atoms?

A

the stable elements that the parent elements decay into

57
Q

Parent atoms are the ______ radioactive atoms

A

unstable

58
Q

Daughter atoms are the _____ elements that the parent elements decays into

A

stable

59
Q

If you know the half life of an element and the initial concentrations of parent and daughter atoms you can calculate…

A

age.

60
Q

The oldest sedimentary rock mineral has been dated to _____ billion years

A

4.4

however we know that sedimentary rocks are formed from other rocks, so we would assume that there was an older rock that formed the sedimentary rock

61
Q

We determine the age of the Earth by coming at it from a ______ way, with the assumption, and strong evidence, that the whole solar system formed in the same event

A

roundabout

62
Q

By assuming that the whole solar system formed in the same event, what can we assume?

A

that the earth is the same age as the rest of the planets and the rest of the material in the solar system

63
Q

What is the Allende meteorite?

A

a carbonaceous chondrite,

64
Q

a carbonaceous chondrite contains tiny amounts of ______

A

carbon

Earth Science (42 decks)

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