Organization of Ch 2124 Ch 211 Describes the geologic time scale Ch 22 Precambrian Earth Section 1 Early Earth Section 2 Formation of the Crust and Continents Section 3 Formation of the Atmosphere and Oceans ID: 645043
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Slide1
Geologic Time
Chapter 21.1, 22, 23, 24Slide2
Organization of
Ch
21-24
Ch
21.1 – Describes the geologic time scale
Ch
22 – Precambrian Earth
Section 1: Early Earth
Section 2: Formation of the Crust and Continents
Section 3: Formation of the Atmosphere and Oceans
Section 4: Early Life on Earth
Ch
23 – Paleozoic Era
Ch
24 – Mesozoic and Cenozoic ErasSlide3
Ch
21.1 Section Assessment Questions,
pg
556: 1-7
How did geologists determine the divisions of the geologic time scale?
What does the geologic time scale indicate about the change in life-forms over time?
What do the names of the three eras of the Phanerozoic mean?
What major change occurred in life-forms at the end of the Proterozoic?
How were the geologic time periods named? On what basis are they defined?
Why is the use of living faunas acceptable for defining the periods and epochs of the Cenozoic Era?
Make bar graph showing breakdown of the scale.Slide4
Why do we care?
By studying the characteristics of rocks and fossils within them, geologists can interpret
The environment the rocks were deposited in
Reconstruct Earth’s history
Possibly predict events or conditions of the futureSlide5
Geologic Time Scale
Defn
: record of Earth’s history from its origin to the present used by scientists around the world to correlate:
G
eologic events
Environmental changes
Development of life-forms that are preserved in rocks
Names of periods don’t change, but the years marking the beg. and end are continually being refined.Slide6Slide7
Geologic Time Divisions
Eon
– longest unit, measured in billions
Era
– next-longest, hundreds of millions to billions
“Paleozoic” = old life
“Mesozoic” = middle life
“Cenozoic” = recent life
Period
– 10’s to 100’s of millions of years
Epoch
– smaller divisions, millions to 10’s of millionsSlide8
Eons
Longest
unit
Measured
in
billions
Three Eons
Archean Eon
(
part 1 Precambrian Time
)
NO LIFE
Proterozoic Eon
(
part 2 Precambrian Time
)
SINGLE-CELLED LIFE
Phanerozoic Eon
(
3 Eras
)
MULTICELLULAR LIFESlide9
Eras
Next
-
longest
Hundreds
of millions to
billions
Defined by differences in life-forms found in rock
Three Eras
“Paleozoic” = old life
“Mesozoic” = middle life
“Cenozoic” = recent lifeSlide10
Periods
Second shortest
10
’s to 100’s of millions of
years
Defined by life-forms that were abundant or became extinct during the time the rocks were depositedSlide11
Epochs
Smaller divisions
Millions
to 10’s of
millions
ONLY IN CENOZOIC
…
WHY?Slide12
Precambrian
Time (Early Earth)
Makes up the
first 90%
of geologic
time
Age of Earth
Land
Atmosphere
Oceans
LifeSlide13
How old is Earth?
4.6 billion years old
Evidence?
Rock age
–
3.96 by (radiometric dating)
Zircon minerals
–
4.1-2 by (radiometric dating)
Meteorites
–
4.5-7 by (radiometric dating)
Moon rocks
–
4.6 by (radiometric dating)Slide14
Land
How did land form?
Earth cooled and crust formed
Early crust used to be mainly basalt.
Densities of different materials sorted out the layers of earth (
differentiation)
Melting
of basaltic crust and then
recrystallization
formed granitic crust
.
Why is the iron and nickel outer core liquid but inner core solid? More pressure in inner core increases its melting point. Less pressure in outer core
.
Early Earth
molten rock Present continentsSlide15
Atmosphere
Early Earth
Carbon dioxide (CO
2
), N
2
, Methane (CH
4
), Water vapor (H
2
O), Carbon monoxide (CO), Ammonia (NH
3
)
HOT TEMPS
Present Earth
N
2
(71%),
O
2
(21%),
Ar
(0.9%), CO
2
How?! Stromatolites!
Evidence?! Red beds!
Avg
global temp is 25 degrees CelsiusSlide16
Oceans
Early Earth
NO OCEANS
Present Earth 71% OCEANS!
HOW?!
Meteorites and comets brought water
Volcanoes released during Archaean Eon (outgassing)
LOTS OF RAINSlide17
Resources
Climate Resource
http://
www.scotese.com/climate.htm
Landmass Resource
http://
www.scotese.com/earth.htmSlide18
ERAS
Landforms
Flora (plants)
Fauna (animals)
Extinctions
ClimateSlide19
Paleozoic Era - Landforms
- First supercontinent “
Rodinia
” had just broken apart
- Plate tectonics, mountain building Slide20
Paleozoic Era - Flora
- Rainforests covered the earth
- Vascular plants appeared (allowed for taller, stronger plants)
- Ferns Slide21
Paleozoic Era - Fauna
- Reptiles appear
- Amphibians
- Fishes w/backbones (
vert
)
- Trilobites (org w/hard parts)
- Marine life!!
- (
Stromatolites
in Precambrian) Slide22
Paleozoic Era - Extinctions
- End of Paleozoic Era was the Permian Extinction (more than 90% of species died)
- 1
st
mass extinction ended the
Ordovican
period (marine life)Slide23
Paleozoic Era - Climate
- Global cooling continued
- Ranged from temperate to cold to steamy swamp Slide24
Mesozoic Era - Landforms
- Breakup of “Pangaea”
- Tectonic activity, mountain building
- Sea levels rose Slide25
Mesozoic Era - Flora
- Flowering plants first evolved Slide26
Mesozoic Era - Fauna
- Birds evolve
- Dinosaurs, Crocodiles, early mammals evolve, ocean/air reptiles evolve Slide27
Mesozoic Era - Extinctions
- Cretaceous extinction ended Mesozoic era and rid dinosaurs Slide28
Mesozoic Era - Climate
- Sandy, desert interior
- Poles moist, temperate
- Mild Slide29
Cenozoic Era - Landforms
- Major tectonic activity, continents moved to their current positions Slide30
Cenozoic Era - Flora
- Grasslands spread
- Many more flowering plants Slide31
Cenozoic Era - Fauna
- Hominids, humans, cats, whales, bats
Slide32
Cenozoic Era - Extinctions
- Due to changes in CO
2
, we could be entering the world’s next extinction?
- Just like the extinction that killed the dinosaurs? Slide33
Cenozoic Era - Climate
-
Most recent ice
age
- Climate
changed back and forth, warmer and cooler