geologic history
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Geologic History. Topic: Geologic Time. Objectives: Day 1 of 3 I will know the major geologic events that have transformed our earth I will know the geologic time scale and it’s major divisions. Quickwrite:. In 2-3 sentences answer one of the questions below: - PowerPoint PPT PresentationTRANSCRIPT
Geologic History
Topic: Geologic Time
Objectives: Day 1 of 3
• I will know the major geologic events that have transformed our earth
• I will know the geologic time scale and it’s major divisions
Quickwrite:
In 2-3 sentences answer one of the questions below:
• What do you think a mass extinction is???• If you know what a mass extinction is, what
do you think causes them????• Considering the age of the earth 4.6 BYO,
When do you think life first appeared??
• The geological time scale is the geologic history of the planet from formation to the present.
• It is starts with large divisions of time called eons and is subdivided into successively smaller units such ass eras and period
• The geologic time scale is based on dominant lifeforms, and mass extinction events
Geologic Time Scale
Geologic Time ScaleSome of the major time
eras include the:
• Precambrian Oceans and atmosphere form
• Paleozoic Invertebrates, plants and fish are the
dominant forms of life
• Mesozoic Reptiles are the dominant forms of life
• Cenozoic Mammals are the dominant forms of life
What is the Geologic Time Scale?
• Time scale from the beginning of earth to present
• It is broken into time divisions such as Eras, & Periods that are based on the ____record, dominant life forms, and mass ____events
Answer BankExtinction
90%MeteoritesExplosion
FossilOxygenHumans
Photosynthesis
It was a harsh environment.Meteorites bombarded our earth
And volcanoes spewed out gases
Our oceans slowly formed over millions of yearsAs volcanoes released steam
One of these gases was steam or (H2O)
4.6 billion years agoEarth Forms
CO2N2CO2CO2H2OH2OH2O
This was what our planet was like for 4 billion years--90% of earth’s History
Scientists call this period the Precambrian
Precambrian
During the Precambrian, our oceans and atmosphere formed
along with other important events
Steam cooled and condensed into clouds,These clouds Released precipitation (rain) for
millions of years, eventually forming our oceans
Welcome to Earth 4.6 Billion Years ago
4.6 billion years agoEarth Forms
CO2CO2CO2
Precambrian
Another gas given off by volcanoes is Carbon Dioxide (CO2)
These microscopic phytoplanktonabsorbed CO2 from volcanoes and through
Photosynthesis released Oxygen (O2) into our atmosphere
Another important event during the Precambrian was the appearance
of the first single celled forms of life
These phytoplankton were very important Because they helped create an oxygen
rich atmosphere for life to thrive in
About 2 billion years ago, primitive microscopic single celled forms of life called
Phytoplankton began to fill the oceans
Remember the recipefor Photosynthesis is:
CO2 + H2O O2 + C6H12O6
O2O2O2
As Oxygen fill our atmosphere, Our skies eventually became Blue
How did our atmosphere become rich in oxygen?
• Primitive phytoplankton and algae bacteria called stromatolites released oxygen into our atmosphere through
_____ about 2 bya
Answer BankExtinction
90%MeteoritesExplosion
FossilOxygenHumans
Photosynthesis
PrecambrianPrecambrian
3.8 bya- first oceans form
2 bya- oxygen rich atmopshere forms
3.5 bya- 1st single celled forms of life
Major Geologic Events of the Precambrian Era
1.1bya-1st continentRhodinia forms
1.3 bya- first multi celled forms of life
4.5 bya- Moon forms
What are major geologic events of the Precambrian Era?
• 3.8 bya- oceans form
• 3.5 bya- 1st single celled forms of life
• 2 bya- ____ rich atmosphere forms
• 1.3 bya- 1st multi celled forms of life
• 1.1bya-1st continent Rhodinia forms
Answer BankExtinction
90%MeteoritesExplosion
FossilOxygenHumans
Photosynthesis
Some of these animals included trilobites,ammonites (squid like creatures with shells)
Paleozoic EraThe Paleozoic Era witnessed an explosion of life
Very shallow seas covered most of the earth
PrecambrianPrecambrianPaleozoic
Paleozoic
Through out these shallow seas lived some of the first complex forms of life Including: invertebrates (shell fish), fish and plants
PrecambrianPrecambrian
Major Geologic Events of the Paleozoic Era
Paleozoic
Paleozoic
PrecambrianPrecambrian
Paleozoic
Paleozoic
570 mya- Explosion of life
536 mya- 1st fish & invertebrates appear
513 mya- First land plants appear
322 mya- First reptiles appear
245 mya- Mass Extinction 90% of all life
Major Geologic Events of the Paleozoic Era
What are major geologic events of the Paleozoic Era?
• 570 mya- _____ of life• 536 mya- 1st fish & invertebrates
513 mya- 1st land plants • 322 mya- 1st reptiles appear• 245 mya- Mass Extinction ___%
of all life
Answer BankExtinction
90MeteoritesExplosion
FossilOxygenHumans
Photosynthesis
Mesozoic EraThe Mesozoic Era was the age of reptiles & witnessed the evolution of the largest animals to have ever walked the earth PrecambrianPrecambrian
Paleozoic
PaleozoicM
esozo
ic
Meso
zoic
The dinosaurs would eventually go extinct and give rise to modern day birds
However, as we all know, these dinosaurs died Out and left a world for other animals to inherit
Dinosaur Demise
• There is mounting evidence that a large meteorite impact slammed into earth 65 mya ending the Cenozoic era
• This impact would have caused widespread devastation and fires
Dinosaur Demise
• Ash and smoke from fires could have blocked out enough sunlight changing the global climate; decimating and wiping out the cold blood reptiles
PrecambrianPrecambrian
Major Geologic Events of the Mesozoic Era
Paleozoic
PaleozoicM
esozo
ic
Meso
zoic
PrecambrianPrecambrian
Paleozoic
PaleozoicM
esozo
ic
Meso
zoic 200 mya- First Mammals appear
180 mya- Pangea breaks up
160 mya- First Birds appear
65 mya- Mass extinction 60% of all life perishes
200 mya- First Mammals appear 200 mya- First Mammals appear
Major Geologic Events of the Mesozoic Era
What are major geologic events of the Mesozoic Era?
• Reptiles dominate• 200 mya- 1st small Mammals appear• 180 mya- Pangea breaks up• 160 mya- 1st Birds• 65 mya- Mass extinction 60% of all life
perishes including dinosaurs due to large ______collision
Answer BankExtinction
90%MeteoritesExplosion
FossilOxygenHumans
Photosynthesis
Cenozoic EraWith Dinosaurs gone, Mammals would inherit
the earth and dominate the landLarge mammals thrive such as
Horses, Mammoths, and Primates
Mankind would evolve and inhabit the earth expanding it’s population
Many Ice Ages came in went causing the extinction of many large mammals
PrecambrianPrecambrian
Paleozoic
PaleozoicM
esozo
ic
Meso
zoic
Cen
ozo
icC
eno
zoic
PrecambrianPrecambrian
Paleozoic
PaleozoicM
esozo
ic
Meso
zoic
Cen
ozo
icC
eno
zoic
Major Geologic Events of the Cenozoic Era
Major Geologic Events of the Cenozoic Era
PrecambrianPrecambrian
Paleozoic
PaleozoicM
esozo
ic
Meso
zoic
Cen
ozo
icC
eno
zoic
45 mya- One of the largest Ice ages occur
7 mya- First Human Ancestors appear
300,000 ya- Modern humans appear
What are major geologic events of the Cenozoic Era?
• Mammals dominate
• 45 mya- Major ice age event
• 7 mya- 1st Human ancestors appear
• 300,000ya- 1st modern ____• Present- your writing this down!!!!! (do not
write )
Answer BankExtinction
90%MeteoritesExplosion
FossilOxygenHumans
Photosynthesis
Summarize:
List the events in order: Oldest to youngest
• Mammals dominate the earth• Mass extinction 90% of all life wiped out• Reptiles dominate the earth• Explosion of life• Phytoplankton create oxygen rich atmosphere• Mass extinction 65% of all life wiped out including
dinosaurs
Topic: Relative Dating
Objectives: Day 2 of 3
• To learn how scientists use relative dating techniques to put geologic events in order
• To learn how to apply the laws of geology (the law horizontality, law of superposition, law of cross-cutting relationships) to relative dating
Quickwrite:
In 2-3 sentences answer one of the questions below:
• How do you think scientists know which fossils are older and which fossils are younger?
• Imagine you have a full trash can, where would you find the old trash??? Where would you find the new trash???
Relative Dating• In our last notes, we learned
the history of the earth, when reptiles first appeared, when dinosaurs went extinct, when mammals dominated earth
• So how do we know the order of all these events?
• One way scientist’s have figured out Earth’s History is by Relative Dating
Relative Dating• Relative Dating is the concept of dating rocks
by putting geologic events in order• It does not give an exact age of rocks
3.
2.
1. 4. Magma Intrusion
8.
7.
5. Fault cuts through
What is Relative Dating?• The concept of dating rocks by putting
geologic events in_______
3.
2.
1. 4. Magma Intrusion
8.
7.
5. Fault cuts through
Answer BankYounger
gapTop after
BottomOrder
flat
Law of Superposition
3.
2.
1.
• In layers of deposited sedimentary rock, the oldest rock layers are at the bottom and the rock layers become younger toward the top
• Therefore, older fossils would be ath the bottom and younger fossils would be closer to the top
Law of Superposition• Principle of Superposition: States that the
oldest rock layers are at the bottom and the rock layers become younger toward the top
The Law of Superposition: Old rocks formed on the bottom and young rocks are at the top
Young rocks
are at the top
Old rocks are
at the bottom
What is the Law of Superposition?
3.
2.
1.
• In layers of deposited sedimentary rock, the oldest rock layers are at the ____ and the rock layers become younger toward the ____
Answer
BankYounger
gapTop after
BottomOrder
flat
Law of Horizontality
Law of Horiz
ontality:
Rocks f
all into
place fo
rming fla
t,
horizontal la
yers
Law of Horizontality Sediments are originally deposited in flat horizontal layers. If
the rocks are folded or are laying at a steep angle, they must have been disturbed or tilted after they were originally
deposited.
3.
2.
1.
3.
2.
1.
What is the Law of Horizontality?
Sediments are originally deposited in ____ horizontal layers. If the rocks are folded or at an angle, they must have been
disturbed _____they were originally deposited.
3.
2.
1.
3.
2.
1.
Answer Bank
YoungergapTop after
BottomOrder
flat
Unconformities• Think of layers of rock as pages of a history
book • If we remove pages, the book is incomplete• An unconformity is when layers of rock are
missing
3.
2.
1. 1.
3.
Unconformities:Here’s how it works!!!!
3.
2.
1.
5.
4.3. Unconformity(weathering and erosion
create a gap in geologic time)
Unconformities• An unconformity is a gap in rock layers due to
erosion and weathering or a break in the depositing of sediments (missing rock layers)
3.
2.
1. 1.
3.
What is an Unconformity?• An unconformity is a ____ in rock
layers due to erosion and weathering or a break in the depositing of sediments (missing rock layers)
3.
2.
1. 1.
3.
Answer BankYounger
gapTop after
BottomOrder
flat
3.
2.
1. 4. Magma Intrusion
5. Fault cuts through
Law of Cross Cutting Relationships
• The law of cross cutting relationships states that a fault line or an igneous intrusion must be younger than the rock it cuts across.
3.
2.
1. 4. Magma Intrusion
5. Fault cuts through
What is the Law of Cross Cutting Relationships?
• A fault line or an igneous intrusion must be _____ than the rock it cuts across.
Answer BankYounger
gapTop after
BottomOrder
flat
Practice:Start with the oldest rock and work your way to the youngest
C
B
A D Magma Intrusion
H
G
E Fault cuts through
Young1.2.3.4.5.6.7.8.Old
F
A
B
C
D
EF
GH
C
B
A D Magma Intrusion
H
G
E Fault cuts through
F
Practice:Start with the oldest rock and work your way to the youngest
C
B
A D Magma Intrusion
H
G
E Fault cuts through
Young1.2.3.4.5.6.7.8.9.Old
F
A
B
C
D
EF
GH
C
B
A D
H
G
E
FKK
K
Summary:• The law of ______ states that
Sediments are deposited in flat horizontal layers
• When rock layers are missing in the geologic record we call it an _______
• The law of ____ ____ relationships states that A fault line or an igneous intrusion must be younger than the rock it cuts across.
Answer Bank
unconformityhorizontality
Cross-cuttingsuperposition
Topic: Absolute Dating
Objectives: Day 3 of 3
• I will know how scientists use absolute dating to determine the exact age of rocks
• I will know the concept of half life and radioactive decay
Quickwrite:
In 2-3 sentences answer one of the questions below:
• If you shook up 100 pennies in a box, how many do you think would be heads???? How many do you think would be tails????
• Let’s say you have 100 dollars and you can only spend half of it every day. How much money would you have after 2 days????
Absolute Dating• How do we know the earth is
4.6 billion years old?• How do we know when
dinosaurs went extinct?• We can answer those questions
by using Absolute Dating• Absolute Dating is a method
used by geologists to determine the exact age of a rock or fossil
• By analyzing the properties of atoms in rocks and fossils we can get a really accurate date for when the rock or fossil formed
What is Absolute Dating?
• Absolute Dating is a method used by geologists to determine the exact _____ of a rock or fossil
• Different from relative dating because it gives an exact age
Answer Bank
ElementAge
determinedecay
Radioactive Decay• Radioactive Decay: The decay of one
element into another element, • An example would be when Uranium
becomes Lead• Uranium is the parent material and lead is the
what we call the daughter materialUranium Lead
Uranium Atom
Parent Material (unstable) Daughter Material (stable)
Lead Atom
What is Radioactive Decay?• The decay of one element into
another _____
• Ex. Uranium, the unstable parent material decays into the stable daughter product Lead
Answer Bank
ElementAge
determinedecay
Uranium Lead
Uranium Atom
Parent Material (unstable) Daughter Material (stable)
Lead Atom
• Half life is the time it takes for half of the of the parent material to decay
• For example, suppose I have a rock sample that has 100 atoms of Uranium in it
• The Half-Life of Uranium is 4.5 billion years
• So after 4.5 billion years (1 half life) half of the Uranium will have decayed into Lead
• So after 1 half life, you are left with 50% Uranium and 50% Lead
Half-Life
1 half life = 4.5 by
= Uranium
= Lead
50 atoms of Uranium
50 atoms 50 atoms of Leadof Lead
• How much Lead and Uranium is left after another 4.5 billion years (2 half lives) ?????
• Lets find out!!!!!• The Half-Life of Uranium is
4.5 billion years• So after another 4.5 billion
years (2 half lives) half of the Uranium will have decayed into Lead
• So after 2 half lives, you are left with 25% Uranium and 75% Lead
Half-Life
= Uranium
= Lead
second half life = 4.5 by
25% Uranium
75% Lead
• How much Lead and Uranium is left after another 4.5 billion years (3 half lives) ?????
• Lets find out!!!!!• So after another 4.5
billion years (3 half lives) half of the Uranium will decay into Lead
• So after 3 half lives, you are left with 12.5% Uranium and 87.5% Lead
Half-Life
= Uranium
= Lead
1st Half Life = 4.5 by
12.5% Uranium
87.5% Lead87.5% Lead
2nd Half Life = 4.5 by
3rd Half Life = 4.5 by
What is Half life?• Half life is the
time it takes for half of the of the parent material to _____
• Ex. Uranium has a half life of 4.5 billion years
Answer Bank
ElementAge
determinedecay
1 half life = 4.5 by
50 atoms of Uranium
50 atoms 50 atoms of Leadof Lead
Who thinks they understand half-life?
1) What is the half life of uranium-238?
2) According to this diagram, how much uranium remains after 4.5 Billion years? Lead?
3) After 9 billion years, how much uranium is left? Lead?
= parent material
= daughter material
½ life = 50,000 yrs
50,000 yrs
100% Parent Material
50,000 yrs
50% Daughter Material50% Parent Material
75% Daughter Material25% Parent Material
87.5% Daughter Material12.5% Parent Material
Number of Half Lives
Am
ount
of
Par
ent
Mat
eria
l
75
100
50
2550,000 yrs 50,000 yrs 50,000 yrs
1 2 3 4 50
Old vs. Young Rock• We use Uranium half life to measure the age
of the earth, which is very old• But, how would we measure something that is
younger, like tree rings or artifacts from an ancient land?
• Because Carbon-14 ( a radioactive form of carbon) has a half-life of 5,730 years, we can use it to date rocks that are much younger (unlike uranium, which has a half-life of 4.5 billion years)
• After 5,730 years Carbon-14 will decay into stable Nitrogen
Radiometric Dating• To a geologist who studies rocks
in order figure out earth’s history, these radioactive elements that decay are like a clock ticking away, keeping track of time since that’s passed since earth formed
• Radiometric dating has allowed us to figure out Earth’s history in chronological sequence
• Radiometric Dating: A dating method that uses the rate of decay of radioactive atoms in rocks by the amount of parent and daughter product to determine the absolute age of a rock
What is Radiometric Dating?
• Dating method that uses the rate of decay of radioactive atoms in rocks by the amount of parent and daughter product to _____ the absolute age of a rock
Answer Bank
ElementAge
determinedecay
Summarize:• Read the following scenario to complete the
answer below: A piece of coal (made of carbon) from a cave man’s fire is found to have about 50% Carbon-14 and 50% Nitrogen. The half life of Carbon-14 is 5730 years.
1. Carbon-14 is the _____ material and Nitrogen is the _____material
2. ______ is the half life of Carbon-143. The caveman’s coal and fire is ______years
old4. Scientist’s use _____dating to determine the
absolute ____of rocks and fossils
Answer BankParentage
DaughterRadiometric
5,730
100%Carbon-14
5,730years50%
Carbon-1450%
Nitrogen