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Geologic History. This unit will help you develop an understanding of the history of our planet . Formation of the Universe. Big Bang Theory —the most accepted scientific theory of the origin of the universe.

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geologic history

Geologic History

This unit will help you develop an understanding of the history of our planet

slide2

Formation of the Universe

Big Bang Theory—the most accepted scientific theory of the origin of the universe

Def.: Theory that the whole universe began as a dense mass that exploded and expanded outward approximately 13-15 billion years ago

* Still expanding today!!!

* All the gases and dust from the explosion formed everything in the universe

slide3

The Earth is about 4.5 billion years old. That means that approximately 9 billion years went by between the formation of the universe and the formation of the Earth!!!!

slide5

Outgassing

The constant volcanic eruptions gave off a great deal of gas

outgassing produces early atmosphere consisting of
Carbon dioxide

Hydrogen

Helium

Ammonia

Methane

Sulfur Dioxide

Others

Outgassing produces early atmosphere consisting of:
slide7

Earth was being bombarded with meteorites too!! One was big enough to cause part of the molten Earth to “splash” off and form the moon—and it was really close to us! It has slowly moved farther away

Eventually an atmosphere did form and the gases formed clouds and rain (liquid versions of the chemicals listed earlier) began to fall (cooling the hot planet) and made oceans.

slide8

Microscopic organisms(bacteria) evolved in the oceans 4.1 billion years ago

These organisms eventually evolved the ability to perform photosynthesis

(converting sunlight and carbon dioxide into food and giving off oxygen as a waste product)

Cyanobacteria

3 billion years ago

slide9

Microscopic organisms(bacteria) evolved in the oceans

These organisms evolved the ability to perform photosynthesis

(converting sunlight and carbon dioxide into food and giving off oxygen as a waste product)

slide10

Colonies of Cyanobacteria are called STROMATOLITES. Fossilized stromatolites have been found all over the world

photosynthesis
Photosynthesis

Carbon Dioxide

Oxygen

A few billion years of evolution produced plants and other organisms that turn carbon dioxide into oxygen through photosynthesis.

CO2 + sunlight  energy (food for plant) + oxygen

slide12

This new oxygen production changed our atmosphere and harsh environment into the earth we live in today!

slide13

Geologic Time Scale

Mainly on the basis of fossil evidence, geologists have been able to break down geologic time into divisions.

Fossil -the remains or evidence of something once living

Use the ESRT!!! There is A TON of information crammed onto pages 8 & 9

Also…you must remember that MOST sedimentary rocks form in the water and that MOST invertebrate organisms lived in the water

slide14

Evolution—by studying fossils, paleontologists (scientists who study fossils) make observations, finding patterns in life forms and theorize that organisms have changed throughout geologic history

slide15

Evolution—by studying fossils, paleontologists (scientists who study fossils) make observations, finding patterns in life forms and theorize that organisms have changed throughout geologic history

Sweet Video – A Brief History of Life on Earth

slide17

How much time is represented by each of these little boxes?

100 million years

How much time is represented by each of these larger boxes?

500 million years

slide18

Tells us how long ago all the events on this timeline occurred.

How long ago was 4600 mya?

4,600 million years ago

How many zeroes in a million?

4,600,000,000 years ago

slide19

Precambrian

Majority of time on Earth 4,600 - 542 = 4,058 mya

mya = millions of years ago

or 4,058,000,000 years

88% of Earth’s history!

Earth’s beginning

slide20

What part of the Precambrian is when the oceanic oxygen first entered the atmosphere?

Early Proterozoic

The oldest known rocks are from what time period?

Early Archean or early Precambrian

slide21

IMPORTANT:

The timeline on the left side of this line is VERY different from the time line on the right side of this line. Please make this line extra dark and bold in your ESRT!!!

slide22

youngest

Paleozoic

Lasted from 542 mya to 251 mya

oldest

slide23

Indicates the end of the Cambrian period

Indicates the beginning of the Cambrian period

slide24

The next column (EPOCH) breaks periods down into smaller frames of time.

Cenozoic epochs have names whereas the rest are referred to as early, middle and late.

If it is early in a period does that mean it is the beginning or the end?

slide26

The next column gives you an idea of the plants and animals present on earth during each time period.

During which time period were the earliest birds?

Late Jurassic

slide27

Bar indicates that there is a complete sediment record for the Quaternary period.

In the Neogene, no bar indicates that there is a missing sediment record. Perhaps sediments never formed OR erosion took place.

slide28

Further down the chart the symbol changes to the rock record. Bar indicates that there is a rock record for the END of the Triassic period and the BEGINNING of the Jurassic period.

slide29

This next section gives a bar graph of different groups of fossils.

How many periods could you find trilobite fossils from?

About 7

slide30

The letters match the pictures at the bottom of your ESRT.

Where you find the letter on the bar helps you to find the period it lived.

slide31

Reading the Important Geologic Events in NY column is similar to reading the other columns. Look for what you need then read horizontally across the ESRT to find the information you are looking for (period, era, epoch, or mya).

Just remember that the globes shown here do not go across horizontally!! You must follow the arrows.

slide34

Evolution—by studying fossils, paleontologists (scientists who study fossils) make observations, finding patterns in life forms and theorize that organisms have changed throughout geologic history

slide36

Relative Dating Vs. Absolute Dating

Relative Dating refers to the determination of agecompared to other events.

Absolute Dating refers to determining the actual age of somethingin years.

slide38

oldest

youngest

slide39

What you have just done is relative dating! Of course, it’s a little bit more difficult than that for a geologist.

slide40

Uniformitarianism—

”the present is the key to the past”—the theory that the geologic processes that are occurring today occurred in the same way in the past.

Law of Superposition—the oldest rocks are deposited first

Youngest rock layer

Oldest rock layer

(Think: laundry basket!)

slide42

Vocabulary Review

Fold—when rock layers are bent/deformed due to tectonic stress (such as plate collisions)

“Bent” rock layers are a fold

Fault

Intrusion of igneous rock

Intrusion—when magma cuts through rock, causing contact metamorphism of the pre-existing rock

Fault—a crack or break in the rocks along which movement has occurred

Extrusion—when magma (lava) cuts through rock and reaches the surface, causing contact metamorphism of the pre-existing rock

slide43

Law of Crosscutting Relationships—therocks were there first before anything altered the rock (such as an intrusion, extrusion, fold, or fault)

Rocks are older

Older

Intrusion is younger

Fault is younger

slide45

Law of IncludedFragments—the sediments within the rock are older than the rock itself.

Older than the whole rock

slide46

Unconformity—a buried erosional surface

unconformity

http://www.classzone.com/books/earth_science/terc/content/visualizations/es2902/es2902page01.cfm?chapter_no=visualization

slide47

Unconformity—a buried erosional surface

unconformity

Unconformities form by

Deposition of sediments that form rocks

Uplift of the rock out of the water

Erosion

Subsidence—the land sank OR sea level rose so that new rocks could form (repeating the cycle again)

slide49

Correlation—matching rocks or geologic events from different places

This is important to figure out the geologic events of an area and locating mineral resources. Important for telling the whole story.

This can be done by:

a.) Index Fossils(see next slide)

b.) Volcanic Ash Layers(each volcanic eruption is unique and the chemical properties of the ash are different)

c.) Meteorite Deposits (every impact is different and the composition of the meteorites, asteroids or comets is also different and the chemical properties of the debris can be studied)

slide51

Index Fossil—the fossil remains of an organism that:

MEMORIZE THESE

1.) lived over a wide geographical area (giving the fossil a large horizontal distribution in the bedrock)

2.) lived for a relatively short period of time (giving the fossil a small vertical distribution in the bedrock)

slide52

Which fossil could be used as an index fossil?

This one is found in all 4 locations

This one is found in too many layers of rock

This fossil can only be found in one layer (small vertical distribution) and can be found in all 4 locations (large geographic distribution)

slide53

STUDY FOR TEST!

  • Test covers :
        • ESRT pages 8 & 9
        • Evolution of the Earth (how planet transformed into the one we have today)
        • LAWS! (Superposition, Crosscutting, Included fragments)
        • Correlation
        • Index Fossils
slide55

Absolute Dating (exact age)

Radioactive Decay—an unstable atom releases particles and electromagnetic energy thus changing into atoms of other isotopes and elements

Isotope: Atoms with the same number of protons, but differing numbers of neutrons.

Isotopes are different forms of a single element.

slide56

Radioactive decay can be used during radioactive dating to determine the age of a rock or fossil

http://science.discovery.com/videos/100-greatest-discoveries-shorts-radiometric-dating.html

slide57

Half-life—the time required for half of the atoms in a given mass of an isotope to decay.

Parent isotope is unstable and changes into the stable daughter product

Half life is not affected by environmental factors such as temperature, pressure, or chemical reactions

A list of isotopes is found on page 1 of the ESRT

slide58

Used for dating:

  • carbon 14 - Fossil wood, shell, bone, fabric and ash between 1,000 and 70,000 years old.
  • potassium 40 – certain mineralsmore than 100,000 years old
  • uranium 238 -Uranium ores and granitic rocks more than 10 million years old.
  • rubidium 87 - Some granitic rocks, sandstones, igneous, sedimentary and metamorphic rocks more than 10 million years old.
slide59

When an animal first died, it contains all of the Carbon-14 it will ever have (100%). Then after one half life, or ____________ years…

Hint: Use ESRT pg 1

100% Carbon-14

Key: = C-14

slide60

After one half life, or 5,700 years—use ESRT page 1, there will be 50% C-14 and the rest of the C-14 will decay into Nitrogen-14.

1 half-life

50% C-14

and

50% N-14

100% Carbon-14

Key: = C-14 and = N-14

slide61

After a second half life, or a total of 11,400 years, there will now be 25% C-14 (cut it in half again) and then N-14 will increase to 75%.

1 half-life

1 half-life

25% C-14 and

75% N-14

50% C-14 and

50% N-14

100% Carbon-14

Key: = C-14 and = N-14

slide62

If this process continues, will there ever be 0% C-14 and 100% N-14?

No, because you cannot divide a number in half to get zero.

Radioactive decay will continue for a long time, but the numbers will keep getting smaller and smaller & eventually will become so small that it will be too hard for scientists to measure.

slide63

unstable

stable

slide64

Percent parent vs. daughter

fractions

You have to know the half life before you can figure out the rest!

Half-life

grams

# of years

slide65

A paleontologist finds a fossilized bone and wants to determine the age of the bone. After further studies, he discovers that the bone contains 1/8 C14 and 7/8 N14.

How many half-lives have gone by?

How old is the bone?

Use the ESRT to determine the half-life of Carbon-14.

slide66

A paleontologist finds a fossilized Elliptocephalaand wants to determine the age of the bone.

Should the paleontologist use Carbon-14? Why or why not?

slide67

Using radioactive decay, a bone has been dated to be 388 million years old.

Which geologic period is this bone from?

Which geologic era?

Which animal(s) could this bone belong to?

Devonian

Paleozoic

Fish, amphibian, ammonoids, or sharks

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