Geologic Time Scale & Age of Earth

Question 1

______ time puts numbers and dates on things

Answer 1

absolute

Question 2

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

Answer 2

organizing

Question 3

The geologic time scale is a visual ________ of geologic time

Answer 3

representation

Question 4

What is the geologic time scale?

Answer 4

a visual representation of geologic time

Question 5

The geologic time scale is based on…

Answer 5

the succession of rock layers

Question 6

The geologic time scale is divided into:

Answer 6

Eons-> Eras -> Periods -> Epochs

Question 7

What is the Precambrian supereon?

Answer 7

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

Question 8

About 600 million years ago we began which eon?

Answer 8

Phanerozoic

Question 9

The Phanerozoic eon includes which three eras?

Answer 9

Paleozoic, Mesozoic, Cenozoic

Question 10

The Paleozoic era was marked by…

Answer 10

single cell life that developed into mostly ocean-dwelling creatures

Question 11

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

Answer 11

single, ocean

Question 12

The Mesozoic Era was the Age of the…

Answer 12

Dinosaurs

Question 13

The Cenozoic Era has been named the Age of the…

Answer 13

Mammals

Question 14

which eon are we currently in?

Answer 14

the Phanerozoic eon

Question 15

which era are we currently in?

Answer 15

the Cenozoic era

Question 16

What are Eras further divided up into?

Answer 16

Periods

Question 17

how long to periods last?

Answer 17

millions of years

Question 18

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

Answer 18

fossil groups

Question 19

Some period boundaries are marked by ______

Answer 19

extinctions.

Question 20

Periods are further subdivided into…

Answer 20

epochs

Question 21

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

Answer 21

sedimentation, and thickness of the strata

Question 22

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.

Answer 22

units, deposit

Question 23

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

Answer 23

a constant record of deposition and no weathering/erosion

Question 24

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

Answer 24

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

Question 25

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

Answer 25

freshwater, salt

Question 26

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

Answer 26

90 million years.

Question 27

What were the flaws of Sir Halley's method?

Answer 27

- 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)

Question 28

How can salt content be lost in the ocean?

Answer 28

through biologic, tectonic processes

Question 29

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

Answer 29

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

Question 30

How old did Darwin estimate the Earth to be?

Answer 30

300 million years old

Question 31

who challenged and rejected Darwin's theory/method?

Answer 31

Lord Kelvin

Question 32

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

Answer 32

thermodynamic cooling

Question 33

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

Answer 33

molten rock, 800-1200

Question 34

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?

Answer 34

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

Question 35

How old did Lord kelvin estimate the Earth to be?

Answer 35

20-100 million years

Question 36

what were the flaws with Lord Kelvin's thinking?

Answer 36

- 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

Question 37

what discovery invalidated Lord Kelvin's theory?

Answer 37

the discovery of radioactivity

Question 38

What is radioactivity?

Answer 38

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

Question 39

who discovered radioactivity?

Answer 39

Marie Curie

Question 40

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

Answer 40

breakdown, heat

Question 41

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

Answer 41

theometric dating

Question 42

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

Answer 42

radiometric dating

Question 43

How old do modern scientists estimate the Earth to be?

Answer 43

4.55 billion years

Question 44

Radioactive elements are unstable ______ of an otherwise stable element.

Answer 44

isotopes

Question 45

radioactive elements are important to...

Answer 45

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

Question 46

how any radioactive elements have been discovered?

Answer 46

>1500

Question 47

Radioactive elements are ______

Answer 47

unstable

Question 48

Radioactive elements are unstable which means they _____ into stable _____

Answer 48

decay, stable

Question 49

Decay occurs at _____ rates for each type of radioactive element

Answer 49

different.

Question 50

The rate at which an element decays is known as...

Answer 50

an element's half life

Question 51

a gigabite is ______ bites, a gigayear is _____ years

Answer 51

1 billion, 1 billion

Question 52

What is a half life?

Answer 52

a measure of how quickly a radioactive element decays

Question 53

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

Answer 53

radioactive

Question 54

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

Answer 54

parent

Question 55

What are the parent atoms?

Answer 55

the unstable radioactive atoms

Question 56

What are the daughter atoms?

Answer 56

the stable elements that the parent elements decay into

Question 57

Parent atoms are the ______ radioactive atoms

Answer 57

unstable

Question 58

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

Answer 58

stable

Question 59

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

Answer 59

age.

Question 60

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

Answer 60

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

Question 61

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

Answer 61

roundabout

Question 62

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

Answer 62

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

Question 63

What is the Allende meteorite?

Answer 63

a carbonaceous chondrite,

Question 64

a carbonaceous chondrite contains tiny amounts of ______

Answer 64

carbon