Geologic Time - PowerPoint Presentation

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.Slide6
Slide7

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