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Chapter 2 Chapter 2 Creation of OceansCreation of Oceans

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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.

Big Bang 13 bya

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Origin of a GalaxyOrigin of a Galaxy

Huge rotating aggregation of stars, dust, Huge rotating aggregation of stars, dust, gas and other debris held together by gas and other debris held together by gravity.gravity.

Andromeda Galaxy

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Origin of the Solar SystemOrigin of the Solar System Rotating cloud of gas from which sun and Rotating cloud of gas from which sun and

planets formedplanets formed

Initiated by “supernova” = exploding starInitiated 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

66

Moderate Size Stars (Our Sun): C & O

Large Stars (more, H & He): Fe

Supernova: Heavier Elements Formed

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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.

Hydrogen and helium remain gaseous, but other materials can condense into solid “seeds” for building planets.

Cold temperatures allow “seeds” to contain abundant ice in outer solar system.

Terrestrial planets are built from metal and rock.

Solid “seeds” collide and stick together. Larger ones attract others with their gravity, growing bigger still.

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.

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

Condensation Theory

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The planet grew by the aggregation of particles. The planet grew by the aggregation of particles. Meteors and asteroids bombarded the surface, Meteors and asteroids bombarded the surface, heating the new planet and adding to its heating the new planet and adding to its growing mass. At the time, Earth was composed growing mass. At the time, Earth was composed of a homogeneous mixture of materials.of a homogeneous mixture of materials.

The result of density stratification: The result of density stratification: an inner and an inner and outer core, outer core,

a mantle, a mantle, and the crust.and the crust.

Earth lost volume because of gravitational Earth lost volume because of gravitational compression. High temperatures in the interior compression. High temperatures in the interior turned the inner Earth into a semisolid mass; turned the inner Earth into a semisolid mass; dense iron (red drops) fell toward the center to dense iron (red drops) fell toward the center to form the core, while less dense silicates move form the core, while less dense silicates move outward. Friction generated by this movement outward. Friction generated by this movement heated Earth even more.heated Earth even more.

Earth, Ocean and Atmosphere accumulated in layers sorted by density

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Sources of WaterSources of Water

* Mantle rocksMantle rocksEvidence from meteoritesEvidence from meteoritesRelease through volcanic activityRelease through volcanic activity

* Outer spaceOuter spaceEvidence from Dynamics ExplorerEvidence from Dynamics Explorer

1010Fig. 2-11, p. 49

100Methane, ammonia

75Atmosphere

unknown50 Nitrogen

WaterCon

cent

ratio

n of

A

tmos

pher

ic G

ases

(%)

25Carbon dioxide Oxygen

04.5 4 3 2 1

Time (billions of years ago)

The evolution of our atmosphere

Early atmosphere quite different from today’s

initial rise of O2 2.7 b. y. ago – but conclusive evidence is from 2.3 b. y. ago

1111Fig. 2-15, p. 51

Billions of years ago13 Big bang

Billions of years ago

4.6 Earth forms

11 First galaxies form

4.2 Ocean forms Millions of years ago

3.8 Oldest dated rocks 8003.6 First evidence

of life

Solar nebula begins to form5.5 2 Oxygen

revolution begins

Millions of years ago 66

End of dinosaurs

First fishes appear

510

4.6 50 First marine mammals

Earth forms

0.8 Ocean and atmosphere

reach steady state (as today)

Pangaea breaks apart210

End of dinosaurs

Today 0 Today Today 66 Today 3 Humans appear Today

3.5

Sun's output too low for liquid-water ocean

5The sun swells, planets destroyed

Billions of years in the future

First animals arise

Future

Past

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Age and TimeAge and Time1 billion = 1,000,000,000 or 101 billion = 1,000,000,000 or 1099

Earth is 4.6 * 10Earth is 4.6 * 1099 years old years oldOceans are 4.2 * 10Oceans are 4.2 * 1099 years old years oldOldest rocks date from 3.8 * 10Oldest rocks date from 3.8 * 109 9 years agoyears agoFirst evidence of life dates from 3.6 * 10First evidence of life dates from 3.6 * 109 9

years ago years ago 1 million = 1,000,000 or 101 million = 1,000,000 or 1066

Ocean and atmosphere reach the state we Ocean and atmosphere reach the state we know today 800 * 10know today 800 * 106 6 years ago years ago