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Chapter 2
Creation of Oceans
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Big Bang 13 bya
Supporting Evidence for the Big Bang
•Edwin Hubble discovered spreading of galaxies.
•Cosmic background radiation (the glow left over from the explosion
itself) discovered in 1964.
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Origin of a Galaxy
Andromeda Galaxy
Huge rotating aggregation of stars, dust,
gas and other debris held together by
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gravity.
Origin of the Solar System
 Rotating cloud of gas from which sun and
planets formed
 Initiated by “supernova” = exploding star
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Nuclear Fusion: The joining of atoms under tremendous
temperatures and pressures to create atoms of a
heavier element. In the Sun, four hydrogen atoms are
fused to create each helium atom. Two of the
hydrogen's protons become neutrons in the process
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Moderate Size Stars (Our Sun): C & O
Large Stars (more, H & He): Fe
Supernova: Heavier Elements Formed
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Condensation Theory
A nebula (a large,
diffuse gas cloud
of gas and dust)
contracts under
gravity. As it
contracts, the
nebula heats,
flattens, and spins
faster, becoming a
spinning disk of
dust and gas.
Star will be born in center.
Planets will form in disk.
Warm temperatures allow
only metal/rock “seeds” to
condense in the inner solar
system.
Cold
temperatures
allow “seeds” to
contain
abundant ice in
outer solar
system.
Hydrogen and
helium remain
gaseous, but other
materials can
condense into solid
“seeds” for building
planets.
Terrestrial planets are built
from metal and rock.
Solid “seeds”
collide and stick
together. Larger
ones attract others
with their gravity,
growing bigger still.
Terrestrial planets remain in
inner solar system.
Gas giant planets remain in outer
solar system.
“Leftovers” from the
formation process become
asteroids (metal/rock) and
comets (mostly ice).
Not to scale
The seeds of
gas giant
planets grow
large enough to
attract hydrogen
and helium gas,
making them
into giant,
mostly gaseous
planets; moons
form in disks of
dust and gas
that surround
the planets.
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Earth, Ocean and Atmosphere accumulated in layers sorted by
density
The planet grew by the aggregation of particles.
Meteors and asteroids bombarded the surface,
heating the new planet and adding to its growing
mass. At the time, Earth was composed of a
homogeneous mixture of materials.
Earth lost volume because of gravitational
compression. High temperatures in the interior
turned the inner Earth into a semisolid mass;
dense iron (red drops) fell toward the center to
form the core, while less dense silicates move
outward. Friction generated by this movement
heated Earth even more.
The result of density stratification:
an inner
and
outer core,
a mantle,
and the crust.
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Sources of Water
* Mantle rocks
Evidence from meteorites
Release through volcanic activity
* Outer space
Evidence from Dynamics Explorer
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The evolution of our atmosphere
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Concentration of
Atmospheric Gases (%)
Methane, ammonia
75
Atmosphere
unknown
initial rise of O2 2.7 b. y. ago – but conclusive
evidence is from 2.3 b. y. ago
Nitrogen
50
Water
25
Carbon dioxide
0
4.5
Oxygen
3
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Time (billions of years ago)
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Early atmosphere quite different from today’s
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Fig. 2-11,10
p. 49
Billions of years ago
13 Big bang
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5.5
4.6
Today
0
Billions of
years ago
4.6 Earth forms
4.2 Ocean forms
First galaxies
form
3.8 Oldest dated rocks
3.6 First evidence
of life
Solar
nebula
begins
to form
Earth
forms
Today
Millions of
years ago
800 First animals arise
Past
Millions of years
510 First
ago 66
fishes
End of dinosaurs
2 Oxygen
appear
revolution begins
Pangaea 50 First marine
breaks
mammals
Ocean and 210 apart
0.8
atmosphere
End of
reach steady
dinosaurs
state (as today)
Humans appear
3
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Today
Today
Today
Future
3.5
The sun swells,
planets destroyed
Sun's
output too
low for
liquid-water
ocean
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Billions of years
in the future
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Fig. 2-15, p. 51
Age and Time
1 billion = 1,000,000,000 or 109
Earth is 4.6 * 109 years old
Oceans are 4.2 * 109 years old
Oldest rocks date from 3.8 * 109 years ago
First evidence of life dates from 3.6 * 109
years ago
1 million = 1,000,000 or 106
Ocean and atmosphere reach the state we
know today 800 * 106 years ago
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