The document provides information about Earth's early history and the geological processes used to determine the sequence of events. It discusses how the early Earth had volcanic eruptions that released gases into the atmosphere. Over millions of years, oxygen produced by photosynthesis accumulated in the atmosphere. Scientists use various geological dating methods like examining rock layers, fossils, and radioactive decay to construct a timeline of Earth's history and understand the relative and absolute ages of rocks. The geological time scale divides Earth's history into eons, eras, periods, and epochs.

1. Earth Science Earth’s History
Notes
I. Introduction
a. As we already learned the earth is always changing
b. The history of the earth is told by _________________
___________________________________________
c. It is up to the scientist to figure out the puzzle of these
geological events.
II. Early Earth
a. There is evidence that states that the atmosphere and the
oceans of the early earth ___________________________
_______________________
_________________________
_________________________
_________________________
b. There were large amounts of
i. ____________________
ii. ____________________
iii. _____________________
iv. _____________________
That came out of the earth from a process called ___________
v. The vapor was ________________________________
___________________________________________
c. The early earth was also covered by clouds that formed
precipitation over millions of years that cooled down the hot
surface of the earth and also formed oceans.
d. What is the proof to this?
i. _________________________________
__________________________________
__________________________________
e. Today’s atmosphere is made up of 21% oxygen but the gases of
eth volcanic eruptions do not contain oxygen
i. SO WHERE DID WE GET THE OXYGEN FROM?
1. ______________________________________
______________________________________
______________________________________
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2. Earth Science Earth’s History
Notes
a. Photosynthesis produces extra oxygen that
went into the atmosphere over millions of
years.
III. Sequence of Geological events
i. Knowing the sequence of events that took place during
the formation of the earth’s crust helps us develop a
history of the earth to better understand the earth
ii. Relative age is _______________________________
__________________________________________
1. As shown in the appearance of the rock layers
2. Relative age is not really concerned with the age of
the rocks ______________________________
______________________________________
3. This method uses
a. sedimentary rock layers
b. igneous extrusions and intrusions
c. faults
d. folds
e. continuity
f. similarities of rock
g. fossil evidence
h. and volcanic time markers
As clues to determine what was the probable
sequence of events
iii. The actual age of a rock or a fossil is called __________
1. The best way and more precise ____________
___________________________________
___________________________________
2. EVERY RADIOACTIVE ELEMENT DECAYS
3. How does this work?
a. _______________________________
_________________________________
_________________________
b. Sometimes this changing process goes
through steps
c.
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3. Earth Science Earth’s History
Notes
d. We also know how _________________
_______________________________
e. We use a process of half life. Since we know
how long the half life ( time takes ½ the
isotope to decay) is ______________
_________________________________
_________________________________
b. Chronology of layers
i. The law of superposition
1. ________________
________________
________________
________________
a. This is used to determine the sequence
_______
_________________________________
b. This works as long as the group was not
overturned not had an older rock put over it
c. Igneous Intrusions and Extrusions
i. Igneous Intrusions
1. formed when magma is injected into older rock
layers in the crust
2. younger than rock they are found in
3. look for contact metamorphic rock in layer above
and below the intrusion
ii. Igneous Extrusions
1. rocks that ______________
______________________
2. younger than rock layers below
3. ______________________
______________________
iii. Why do we look at the metamorphic
rock near these two rock formations?
1. The reason is contact metamorphism – (the rock
forming due to the contact of lava)
________________________________
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4. Earth Science Earth’s History
Notes
d. Faults Joints & Folds
i. Folds
1. bends ______________
2. occur ______________
___________________
ii. Faults
1. cracks in rock layers
where some movement has
taken place
2. Faults produce offset
layers.
iii. Joints
1. _________________________
iv. These three rock layer characteristics occur _________
___________________________________________
___________________________________________
v. These three rock characteristics are also ___________
___________________________________________
1. Since the rocks that fold, faults or joints are
there before ________________
e. Internal Characteristics
i. Fragments that occur in a rock as we can understand are
older than __________________________________
________________________________
ii. Cracks and veins in a _________________
_________________________________
iii. Veins – are mineral
____________________________
_________________________________________
iv. Sedimentary rocks are ________________________
__________________________________________.
v. Unconformity
1. Is the ________________________________
2. They are found between two ages of rock levels
3. Usually these ______________________
___________________________________
4. It looks like a buried Erosional
surface
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5. Earth Science Earth’s History
Notes
5. ________________________
________________________
______________________________________
______________________________________
IV. Relative Age
a. We use different correlating techniques to find out how old a
rock really is
b. You have to be careful though to use facts and not inferences
when figuring out this information
i. Correlation is the act of matching rocks of similar age in
different places
1. This is best done when rocks are not covered in
dirt and plants
2. This can be so easy by identifying a certain mineral
type, color and then searching for it in different
places
ii. one technique is called INDEX FOSSILS
a. this is using the remains of animals that are
known to have lived and died in a certain
time period
b. If we find one
____________
____________
____________
____________
____________
c. We also use
Index fossils to
decipher rock
records
i. Organism
___________________________
____________________________
____________________________
d. How does a fossil fit the index profile
i. Easily recognizable
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6. Earth Science Earth’s History
Notes
ii. _______________
iii. ________________
________________
iv. _______________
___________________________
iii. Volcanic Time Marker
1. When a volcano ________________________
____________________________________
____________________________________
2. This may be a time marker if we find a layer of ash
in the layers ___________
______________________________
______________________________
3. This time marker will be very helpful determined
the ages of rocks below and above it
iv. Problems with Correlation
1. It _________________________________
______________________________________
_____________________________________
2. However, it can lead to misinformation
a. With very careful study of 2 like rock
formation they might still be different ages.
b. ________________________________
________________________________
V. Geological Times
a. Rock Record
i. As we just learned that scientist use index fossils (guide
fossils ) to tell how old a rock is.
ii. Scale of geological time
1. scientists have organized the geological time scale
a. ________________
b. ________________
c. ________________
d. ________________
2. each is a more specific amount of time then the
other ones
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7. Earth Science Earth’s History
Notes
Units of geological time
periods
Phanerozoic eon Proterozoic eon Archean eon
Cenozoic Mesozoic Paleozoic
cretaceous
Jurassic
Triassic
a. epochs are more based on fossil evidence
i. However, most of the geological time
is void of fossil records
iii. Scientists suggest the following is the geological time
scale
1. Precambrian (prepaleozoic) era
a. Makes up 85% of the earth’s history
b. ______________________________
______________________________
i. This is because the organisms ______
____________________________
____________________________
2. Paleozoic era
a. Much shorter time period
b. Has an abundant of fossils
c. The first vertebrates, land plants and
animals developed in this era
3. The Mesozoic Era
a. Was even shorter
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8. Earth Science Earth’s History
Notes
b. Fossils of dinosaurs and the earliest
birds and mammals formed
c. Included three periods
i. Triassic
ii. Jurassic
iii. Cretaceous
4. The Cenozoic Era
a. Most recent era
b. Includes the fossils of many modern plants
and mammals, even the appearance of
humans
i. Plate motions and mountain buildings
may also be identified in this time
sequence by using the reference table
b. The Erosional Record
i. Buried erosional surfaces show gaps in the time records
of the rocks
ii. It has been suggested that the fossil record would show
a complete timescale and history of earth IF………………….
1. the superposition and held absolutely true
2. no forces of destruction occurred after the the
beginning of life forms
iii. but it is clear that destructional forces have occurred
and continue to occur
iv. One of the key principles that geologists use to interpret
the Earth’s geological history is the principle of
uniformitarianism
1. This principle states that the geological processes
that change the earth today also changed the
earth in the past
2. There are many different rates and various times
but patterns and agents of change stay the same
c. The geological history of an area
i. Using the information used in the rock record, scientist
can guess the history of an area
ii. To see the various rock portions if NEW YORK check out
your reference guide
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