Download Fossil evidence in rock layers

Earth’s History Test Review
Describe uniformitarianism
uniformitarianism
Earth is constantly changing since its creation
The same forces that changed earth’s surface
millions of years ago, are changing it now
What are those forces?
uniformitarianism
Earth is constantly changing since its creation
The same forces that changed earth’s surface
millions of years ago, are changing it now
What are those forces? Weathering, erosion,
plate movement and resulting landforms and
events (seafloor spreading, creation and
destruction of crust, volcanoes, earthquakes,
mountain building, creation of seas)
What is Continental Drift
What evidence supports it?
Continental Drift Evidence
http://www.britannica.com/science/continentaldrift-geology/images-videos/A-discussion-of-someof-the-evidence-supporting-continentaldrift/182285
•
•
•
•
Matching fossils on separate continents
Matching rock formations on separate continents
Puzzle-like continent shapes
Tropical fossils in arctic climates
Fern fossil found in Antarctica
Lithosphere= crust + upper mantle
Asthenosphere= soft, weak layer of mantle
(magma)
What is the difference between
relative and absolute age?
What is the difference between
relative and absolute age?
Relative age: comparing rock layers and events to
one another to determine age. Phrases such as
older/younger than, first-second-third are used. 3
laws used to do this: original horizontality,
superposition, cross-cutting relationships
Absolute age: finding the actual age, or narrow range
of time, of a rock layer by dating igneous material
found in rock layers or “bracketing” using igneous
volcanic ash. Using the half-life of radioactive
material found in igneous rock allows us to do this.
What is the Law of Original
Horizontality?
What is the Law of Original
Horizontality?
Sedimentary rock is formed in horizontal layers
What is the Law of Superposition?
What is the Law superposition?
In undisturbed sedimentary rock layers, the
oldest layer is at the bottom, youngest layer is at
the top of the rock layers
What is the Law of Cross Cutting
Relationships?
What is the Law of Cross Cutting
Relationships?
Anything that cuts through a rock layer is
YOUNGER than the rock layer it is in
Putting it together to find relative age:
• Earth’s history is revealed in rock layers.
• Sedimentary rock layers contain fossils, intrusions, cracks,
unconformities and folds that tell us what was happening on
earth’s surface at different points in time
• Comparing fossils (index) and rock layers tell us what happened
first, second…..relative age
• Oldest layer is on the bottom, younger on top
• Distortions in rock layers occurred after the layer(s) they
changed
http://study.com/academy/lesson/what-isrelative-dating-law-of-superposition-principlesof-original-horizontality-cross-cuttingrelationships.html
Oldest to youngest……
A
B
C
D
E
F
F
E
C
B
D(
)
A (UNCONFORMITY)
A
B
C
D
E
F
OLDEST TO YOUNGEST…
Y
Y
Z
A
FAULT
Q
D
OLDEST TO YOUNGEST…
Y
OLDEST TO YOUNGEST
X
A
B
C
D
E
F (10 MILLION YEARS OLD)
X
F
A
B
C
D
E
F
X
A
B
C
D
E
OLDEST TO YOUNGEST(BOTH ARE CORRECT)
X
A
B
C
D
E
F (10 MILLION YEARS OLD)
Using the absolute age of the intrusion……
E, D, C, B and A are older than 10 million years old
X
A
B
C
D
E
F (10 MILLION YEARS OLD)
Using the diagram
to the right
1
Describe the age
of the fossil
2
• Using layer 1
• Using layer 4
• Using layer 2
3
4
The fossil is older than layer 1
The fossil is younger than layer 4
The fossil is the same age as layer 2
Using the diagram
to the right
1
Describe the age
of the fossil
2
• Using layer 1
• Using layer 4
• Using layer 2
3
4
Using the diagram
to the right
Describe the age
of the fossil B
1
A
B
C
2
3
4
Fossil B is the same age as fossil C
Fossil B is older than fossil A
1
A
B
C
2
3
4
What makes a good index fossil?
What makes a good index fossil?
• Lived a brief period of time (not found in a lot
of vertical rock layers)
• Lived in a large global area (found in the same
horizontal layers across the globe)
• (Easy to see in a rock layer)
Which of these is probably an
index fossil
GA
G
GA
CG
C
C
CBA
A
B
CA
CA
CB
CB
B
C
AC
Which of these is probably an
index fossil
GA
G
GA
CG
C
C
CBA
A
B
CA
CA
CB
CB
B
C
AC
G…..IT IS FOUND IN A LARGE GEOGRAPHIC AREA (SAME HORIZONTAL LAYERS)
BUT DID NOT LIVE A LONG TIME (MULTIPLE LAYERS)
You have found an area of North Carolina with
an abundance of fossils. What kind of rock are
you looking at?
How do you know?
You have found an area of North Carolina with
an abundance of fossils. What kind of rock are
you looking at? Sedimentary rock
How do you know? Heat and pressure involved
in igneous and metamorphic rock process
destroys remains
What kind of evidence do we get from
ice cores and tree rings?
What kind of evidence do we get from
ice cores and tree rings?
•
•
•
•
Ice core
Tree rings
Global climate evidence
• Ring width  very
specific, local information
Bubbles  CO2 levels in
ancient air indicate temp
about precipitation levels
levels. Also used in current
computer model predictions
• Burn scars  forest fire
of global warming.
evidence
Volcanic ash  evidence of
volcanic eruptions
• Irregular banding 
Pollen  spores evidence of
crowding, wind
environmental conditions
conditions
Tree Ring
Ice Core
Increasing levels of CO2 are linked to increasing global temperatures.
Using isotopes of Carbon we know that in the last 450 years, the increasing
CO2 levels are coming from human burning of fossil fuels, not volcanoes!
Absolute Age
Allows the calculation of ancient rock and fossil
age..puts a number on age
Half life of radioactive material found in volcanic
intrusions & volcanic ash.
(the time it takes half a radioactive parent sample
to break down into a stable daughter material)
How much time has passed if
75% parent material remaining
25% parent material remaining
How much time has passed if
75% parent material remaining ½ yr (6 mos)
25% parent material remaining 2 yrs
Different radioactive isotopes are used to date different materials.
rocks
rocks
rocks
dead organisms,
<57,000 yrs old
• Carbon-14 dating uses a radioactive isotope of
carbon. It has a half life of 5,700 years. It has
a useful time of ~60,000 years. It is ONLY
USED on remains of LIVING THINGS
• Other isotopes (uranium, chlorine..) have very
long half lives (millions of years.) They have a
useful range of millions to billions of years.
They are used to date rock layers, fossils and
remains of NONLIVING THINGS
Geologic Time Scale
• What is it
• How is it divided
• Describe the major time periods
Geologic Time Scale
• What is it? Fossil evidence in rock layers
• How is it divided major events (extinctions & radiations)
• Describe the major time periods
Precambrian: single celled life, most of earth’s
history is in precambrian time, ends with mass
radiation of life
Paleozoic era: most life in the sea, age of
amphibians, ends with mass extinction
Mesozoic era: age of reptiles, dinosaurs, no ice—
humid, ends with mass extinction…meteor strike
Cenozoic era: current, age of mammals
EONS – largest division of time
 1. Hadean
 2. Archean
 3. Proterozoic
 4. Phanerozoic
 #1-3 make up Precambrian Time
 Eons -> Eras -> Periods -> Epochs
 Change in name is due major geologic or climatic
events!!
PRECAMBRIAN TIME
• 90% of Earth’s history
• Lasted nearly 4 billion years of Earth’s
4.6 billion years
• Volcanic ash & dust ->clouds formed >rain
• Single-celled micro-organisms in ocean
at end
• No animals
• No plants
• 3 Eras make up the Phanerozoic Eon:
– Paleozoic Era – “Age of Amphibians”
– Mesozoic Era – “Age of Dinosaurs”
– Cenozoic Era – “Age of Mammals”
Paleozoic Era = “Ancient”
544 mya – 248 mya
All life in ocean until end
Fish developed
Reptiles, Insects, Ferns developed –
moving life onto land at end
• Ends with a Mass Extinction kills 90%
of all ocean species
•
•
•
•
Mesozoic Era = “Middle”
• 248 mya – 65 mya
• Dinosaurs rule!
• Small mammals, birds, flowering
plants
• Ends with Mass Extinction due to
meteor strike off Mexico ->dust cloud
blocked sunlight, killed plant life and
affected food chain
Cenozoic Era =“Recent”
• 65 mya – Present
• Large warm-blooded mammals, modern
birds, flowering plants
• Animals developed migration techniques
• Tertiary Period
• Quaternary Period = last 2 million yrs
– Ice ages
– 1st modern human fossils = 100,000 yrs old
– Humans are 7 seconds of 12 hour clock!!
Why study fossils?
Why study fossils?
They show us how
life has changed
over time. The
Geologic Time
Scale show us how
changes in earth’s
surface & climate
have affected changes
in organisms.
Over time,
Life began as single celled
Organisms and became
More diverse and complex