Dating NotesDating Notes

Donald’s 101 to DatingDonald’s 101 to Dating

Earth Science TriviaEarth Science Trivia If you were contracted to construct a If you were contracted to construct a

timeline of the Earth’s historytimeline of the Earth’s history What are at least 2 things that you would What are at least 2 things that you would

have to study to create the time scale?have to study to create the time scale? What type of scientist could you be?What type of scientist could you be?

Rock Layers and FossilsRock Layers and Fossils Paleontologist (studies fossils) or Geologist Paleontologist (studies fossils) or Geologist

(studies rocks)(studies rocks)

Why is Geological Dating Why is Geological Dating Important in Science?Important in Science?

To know when an organism existed To know when an organism existed and and construct a history of construct a history of prehistoric Earth!prehistoric Earth!

Geological Time Scales are made Geological Time Scales are made by piecing together the fossil by piecing together the fossil recordrecord

The Fossil RecordThe Fossil Record Paleontologists group similar Paleontologists group similar

organisms togetherorganisms together StructureStructure HabitatHabitat LocationLocation

They also arrange organisms in the They also arrange organisms in the order in which they lived, from order in which they lived, from earliest to latestearliest to latest

Geologic Time ScaleGeologic Time Scale A CHRONOLOGICAL record of A CHRONOLOGICAL record of

the life forms and geological events the life forms and geological events in Earth’s historyin Earth’s history

Developed from studying ROCK Developed from studying ROCK LAYERS and INDEX FOSSILSLAYERS and INDEX FOSSILS

But, How Do Scientists Know But, How Do Scientists Know How Old Something is???How Old Something is???

Through the use of 2 dating techniquesThrough the use of 2 dating techniques Relative DatingRelative Dating

Determining the order of events by Determining the order of events by examining the positions of rock layersexamining the positions of rock layers

Absolute DatingAbsolute Dating Determining the age, in years, of an Determining the age, in years, of an

event through the use of technological event through the use of technological tools and teststools and tests

Relative DatingRelative Dating Relies on the Relies on the Principle of Principle of

Superposition!Superposition! Remember…oldest rocks are the Remember…oldest rocks are the

bottom layer etc. etc. etc.bottom layer etc. etc. etc. Used for giving the Used for giving the ORDER ORDER of events of events

ONLY (this is older than this, this is ONLY (this is older than this, this is younger than that)younger than that)

Will Will NOTNOT tell an exact age in years tell an exact age in years

Relative DatingRelative Dating ONE PROBLEMONE PROBLEM Most rock layers are not pristine (they Most rock layers are not pristine (they

have been disturbed)have been disturbed) Uplift, rock layer tilting and Uplift, rock layer tilting and

EROSIONEROSION angle and remove rock angle and remove rock layers causing GAPS in the fossil layers causing GAPS in the fossil record known as…record known as…

UNCONFORMITIESUNCONFORMITIES

UnconformityUnconformity Angular Angular

UnconformityUnconformity - - Result when Result when horizontal horizontal layers lie on top layers lie on top of tilted layersof tilted layers

UnconformityUnconformity Disconformity Disconformity

/Nonconformity/Nonconformity - - Results when top Results when top rock layer is rock layer is eroded away eroded away BEFORE a new BEFORE a new layer is deposited layer is deposited = GAP in record= GAP in record

So what do we really use So what do we really use this for?this for?

Correlation of rock layersCorrelation of rock layers To identify gaps called…To identify gaps called… UNCONFORMITIESUNCONFORMITIES To help us understand early Earth To help us understand early Earth

and continental positioningand continental positioning This means we have to study land This means we have to study land

ALL aver the world!ALL aver the world!

Absolute DatingAbsolute Dating Relies on atoms and their Relies on atoms and their

radioactive decayradioactive decay Assigns a number in years to the Assigns a number in years to the

eventevent

Important VocabImportant Vocab Radioactive DecayRadioactive Decay: When an atom : When an atom

releases energy as it changes to a new releases energy as it changes to a new kind of atomkind of atom

IsotopeIsotope: An atom of the same : An atom of the same element with a different number of element with a different number of neutronsneutrons

Parent MaterialParent Material: Original isotope : Original isotope (pre-decay)(pre-decay)

Important VocabImportant Vocab Daughter MaterialDaughter Material: What the parent : What the parent

becomes as it decaysbecomes as it decays Half LifeHalf Life: The time it takes for : The time it takes for

HALF of the radioactive atoms to HALF of the radioactive atoms to decaydecay

Page 347: Using MathPage 347: Using Math 5 lives have past, 5 x 1600 = 5 lives have past, 5 x 1600 = 8000 years8000 years

Absolute DatingAbsolute Dating Radiometric DatingRadiometric Dating

Age calculation from measuring Age calculation from measuring the parent to daughter material ratio the parent to daughter material ratio and applying the elements half lifeand applying the elements half life

TypesTypes Carbon - 14Carbon - 14 Potassium - ArgonPotassium - Argon

Absolute DatingAbsolute Dating Carbon - 14 Dating:Carbon - 14 Dating: Carbon-14 Carbon-14

decays to nitrogen-14decays to nitrogen-14 ALLALL plants and animals contain plants and animals contain

carboncarbon Scientists measure the amount of Scientists measure the amount of

carbon-14 left in the remainscarbon-14 left in the remains Carbon-14 half life is 5730 yearsCarbon-14 half life is 5730 years

C - 14 ProblemsC - 14 Problems AccuracyAccuracy

Recent = 200 year spanRecent = 200 year span Older = 500-1000 year spanOlder = 500-1000 year span

EXPENSIVEEXPENSIVE DifficultDifficult Sample - Sample - Only useful for dating once Only useful for dating once

living materials UP TO 50,000 years living materials UP TO 50,000 years oldold

Sample Problems Sample Problems

Homework!Homework!

SummarySummary Geologic Dating is important Geologic Dating is important

because…because… Two types of dating are…Two types of dating are… Relative dating is…Relative dating is… Absolute Dating is…Absolute Dating is… They are different because…They are different because…