introduction to geology plate tectonics

Chapter 1

Cosmology and Birth of EarthEarth: Portrait of a Planet, 4th editionby Stephen Marshak

© 2011 W.W. Norton & Company

PowerPoint slides prepared by Ronald L. Parker, Fronterra Geosciences, 700 17th Street, Suite 900, Denver, CO, 80202

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Earth: Portrait of a Planet, 4th edition, by Stephen Marshak © 2011, W. W. Norton Earth: Portrait of a Planet, 4th edition, by Stephen Marshak © 2011, W. W. Norton Chapter 1: Cosmology and the Birth of EarthChapter 1: Cosmology and the Birth of Earth

IntroductionIntroduction

•• Why study the solid Earth?Why study the solid Earth?

•• To discover natural resourcesTo discover natural resources

•• To understand and mitigate against natural disastersTo understand and mitigate against natural disasters

•• To predict the future and develop sustainable To predict the future and develop sustainable environmental policiesenvironmental policies

•• Natural Natural curiousitycuriousity!!

Earth: Portrait of a Planet, 4th edition, by Stephen Marshak © 2011, W. W. Norton Earth: Portrait of a Planet, 4th edition, by Stephen Marshak © 2011, W. W. Norton Chapter 1: Cosmology and The Birth of EarthChapter 1: Cosmology and The Birth of Earth


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To predict future global changeTo predict future global change

�� By studying present environments, By studying present environments,

geologists can associate these with geologists can associate these with

features preserved in ancient rocksfeatures preserved in ancient rocks

�� Geologists can now detect Earth’s Geologists can now detect Earth’s

natural rhythms of global change natural rhythms of global change

over timeover time

�� Earth’s climate history has been Earth’s climate history has been

largely deciphered.largely deciphered.

�� GreenhouseGreenhouse——warmer climates.warmer climates.

�� IcehouseIcehouse——colder climates.colder climates.

Fig. 23.11a


Lecture 1: Cosmology and the Birth of Lecture 1: Cosmology and the Birth of EarthEarth

Lecture 1: Cosmology and the Birth of Lecture 1: Cosmology and the Birth of EarthEarth

Prepared by:Prepared by:

Ronald L. ParkerRonald L. Parker, , Senior GeologistSenior Geologist

Fronterra Geosciences,Fronterra Geosciences,

Denver, ColoradoDenver, Colorado

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IntroductionIntroduction

�� Cosmology: the scientific study of the Universe.Cosmology: the scientific study of the Universe.

�� StructureStructure

�� HistoryHistory

Part 1 Opener


What Is the Structure of the Universe?What Is the Structure of the Universe?

�� Three thousand years ago, people knew the heavens. Three thousand years ago, people knew the heavens. They knew:They knew:

�� The stars are fixed relative to each other.The stars are fixed relative to each other.

�� All the stars rotate about a fixed point.All the stars rotate about a fixed point.

�� The planets move against the background of stars.The planets move against the background of stars.

�� They did They did notnot know that the Earth is a planet, however.know that the Earth is a planet, however.

�� They did They did notnot know how heavenly bodies move.know how heavenly bodies move.

Part 1 Opener



�� The ancients thought the Universe was geocentric. The ancients thought the Universe was geocentric.

�� Heavenly bodies circle around a motionless central Earth. Heavenly bodies circle around a motionless central Earth.

�� The idea held as religious dogma for 1,400 years.The idea held as religious dogma for 1,400 years.

�� Ptolemy (100Ptolemy (100––170 C.E.) proved the idea was wrong. 170 C.E.) proved the idea was wrong.

�� Around 250 B.C.E., the GreeksAround 250 B.C.E., the Greeks

proposed a heliocentric (sunproposed a heliocentric (sun--

centered) Universe.centered) Universe.

Earth

Sun

Fig. 1.1a

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�� Renaissance: A new age of discovery in 1400s Europe.Renaissance: A new age of discovery in 1400s Europe.

�� It spawned a new age of scientific exploration.It spawned a new age of scientific exploration.

�� CopernicusCopernicus——published evidence for heliocentricity.published evidence for heliocentricity.

�� GalileoGalileo——observed moons orbiting Jupiter. observed moons orbiting Jupiter.

�� NewtonNewton——planet motion explained by his Theory of Gravity.planet motion explained by his Theory of Gravity.

�� Natural laws (not deities) govern natural events.Natural laws (not deities) govern natural events.

�� Geocentricity faded away.Geocentricity faded away.


Earth

Sun

Fig. 1.1b


The Nature of Our Solar SystemThe Nature of Our Solar System

�� Telescopes reveal seven other planets in our Solar Telescopes reveal seven other planets in our Solar System.System.

�� PlanetPlanet——a planet:a planet:

��Is a large solid body orbiting a star (the Sun).Is a large solid body orbiting a star (the Sun).

��Has a nearly spherical shape.Has a nearly spherical shape.

��Has cleared its neighborhood of other objects (by gravity).Has cleared its neighborhood of other objects (by gravity).

�� Thus, Pluto, previously defined as a planet, is excluded.Thus, Pluto, previously defined as a planet, is excluded.

�� MoonMoon——a solid body locked in orbit around a planet.a solid body locked in orbit around a planet.


The Nature of Our Solar SystemThe Nature of Our Solar System

�� Two groups of planets occur in the solar system. Two groups of planets occur in the solar system.

�� Terrestrial PlanetsTerrestrial Planets——small, dense, rocky planets.small, dense, rocky planets.

��Mercury, Venus, Earth, and MarsMercury, Venus, Earth, and Mars

�� GasGas--giant Planetsgiant Planets——large, lowlarge, low--density, gasdensity, gas--giant planets.giant planets.

��Jupiter, Saturn, Uranus, and NeptuneJupiter, Saturn, Uranus, and Neptune

�� The Solar System is held together by gravity.The Solar System is held together by gravity.

Fig. 1.2a

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How Do We Know Earth Rotates?How Do We Know Earth Rotates?

�� Earth spins rapidly on an axis of rotation.Earth spins rapidly on an axis of rotation.

�� A timeA time--lapse photo of stars shows this rotation. lapse photo of stars shows this rotation.

�� One spin ~40,000 km per day or ~1,700 kph (1,040 mph).One spin ~40,000 km per day or ~1,700 kph (1,040 mph).

�� Rotation centered on Polaris, the North Star.Rotation centered on Polaris, the North Star.

�� Rotation proven by Foucault’s pendulum (1851).Rotation proven by Foucault’s pendulum (1851).

�� Pendulum swings back and forth in the same plane. Pendulum swings back and forth in the same plane.

�� Earth’s rotation moves the ground beneath the pendulum. Earth’s rotation moves the ground beneath the pendulum.

Box 1.1a,c


�� The terrestrial planets are the four most interior.The terrestrial planets are the four most interior.

�� The gasThe gas--giant planets occupy the four outermost orbits.giant planets occupy the four outermost orbits.

�� The asteroid belt lies between Mars and Jupiter.The asteroid belt lies between Mars and Jupiter.

�� Planet orbital planes lie within 3Planet orbital planes lie within 3°°°°°°°° of the Sun's equator.of the Sun's equator.

�� Consistent with the nebular theory of Solar System Consistent with the nebular theory of Solar System

formation. formation.

The Solar SystemThe Solar System

Fig. 1.2b


Stars and GalaxiesStars and Galaxies

�� Stars are immense balls of incandescent gas.Stars are immense balls of incandescent gas.

�� Light and heat derives from nuclear fusion reactions.Light and heat derives from nuclear fusion reactions.

�� Gravity binds stars together into vast galaxies.Gravity binds stars together into vast galaxies.

�� The Solar System is on an arm of the Milky Way galaxy.The Solar System is on an arm of the Milky Way galaxy.

�� Our sun is one of 300 billion Our sun is one of 300 billion

stars in the Milky Way.stars in the Milky Way.

Fig. 1.3

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Determining Earth’s SizeDetermining Earth’s Size

�� Eratosthenes calculated the circumference in ~200 B.C.Eratosthenes calculated the circumference in ~200 B.C.

�� He measured shadows in deep wells 800 km apart. He measured shadows in deep wells 800 km apart.

�� Measurement taken at noon on the same day. Measurement taken at noon on the same day.

�� SyeneSyene——shadow absent (directly overhead). shadow absent (directly overhead).

�� AlexandriaAlexandria——shadow at 7.2shadow at 7.2oo..

�� He calculated that 800 km was He calculated that 800 km was

1/50th of Earth’s circumference.1/50th of Earth’s circumference.

�� He was correct!He was correct!

�� ~40,000 km~40,000 km

�� ~25,000 miles~25,000 miles

Fig. 1.4


Distance to Celestial ObjectsDistance to Celestial Objects

�� The dimensions of the Universe are The dimensions of the Universe are vast.vast.

�� We must consider huge expanses of space and time.We must consider huge expanses of space and time.

�� The speed of light (The speed of light (cc) is 186,000 miles/s (300,000 km/s).) is 186,000 miles/s (300,000 km/s).

��The Moon is 1.3 lightThe Moon is 1.3 light--seconds (~237,000 miles) away.seconds (~237,000 miles) away.

��The Sun is 8.3 lightThe Sun is 8.3 light--minutes (~93 million miles) away.minutes (~93 million miles) away.

�� A lightA light--year measures a distance of 9.5 trillion km. year measures a distance of 9.5 trillion km.

�� Alpha Centauri, the closest star, is 4.3 lightAlpha Centauri, the closest star, is 4.3 light--years away. years away.

��40.85 trillion km40.85 trillion km

�� Edge of the visible universe: >13 billion lightEdge of the visible universe: >13 billion light--years away.years away.

Part 1 Opener


�� The vastness of the Universe is difficult to conceive.The vastness of the Universe is difficult to conceive.

�� Earth is a planet orbiting a star on the arm of a galaxy.Earth is a planet orbiting a star on the arm of a galaxy.

�� Andromeda, the next galaxy, is 2,200,000 lightAndromeda, the next galaxy, is 2,200,000 light--years away. years away.

�� Beyond Andromeda are hundreds of billions of other Beyond Andromeda are hundreds of billions of other

galaxies.galaxies.

�� Where did all this “stuff” come from?Where did all this “stuff” come from?

�� Observations since the 1920s have provided clues.Observations since the 1920s have provided clues.

Forming the UniverseForming the Universe

Fig. 1.3

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�� Sound waves compress or relax with relative motion. Sound waves compress or relax with relative motion.

�� Compressed: shorter wavelength; higher frequency. Compressed: shorter wavelength; higher frequency.

�� Relaxed: longer wavelength; lower frequency. Relaxed: longer wavelength; lower frequency.

�� A stopped train sounds different than a moving train.A stopped train sounds different than a moving train.

��As the train approaches, a person hears a higher pitch. As the train approaches, a person hears a higher pitch.

��As the train passes, the pitch drops (higher to lower). As the train passes, the pitch drops (higher to lower).

��As the train recedes, a person hears a lower pitch.As the train recedes, a person hears a lower pitch.

��This is commonly heard as cars pass by on a road.This is commonly heard as cars pass by on a road.

The Doppler EffectThe Doppler Effect

Fig. 1.5a,b


The Doppler EffectThe Doppler Effect

�� The Doppler effect influences light waves, too.The Doppler effect influences light waves, too.

�� Visible light is electromagnetic radiation.Visible light is electromagnetic radiation.

�� Visible wavelengths range from 400 and 700 nanometers.Visible wavelengths range from 400 and 700 nanometers.

��400 nm400 nm——blue = higher frequency.blue = higher frequency.

��700 nm700 nm——red = lower frequency.red = lower frequency.

�� Moving light waves reveal the Doppler effect.Moving light waves reveal the Doppler effect.

�� Light moving toward an observer compresses (blue). Light moving toward an observer compresses (blue).

�� Light moving away from an observer expands (red).Light moving away from an observer expands (red).

Fig. 1.5d


The Red ShiftThe Red Shift

�� A moving star displays Doppler shifted light. A moving star displays Doppler shifted light.

�� Approaching starlight is compressed (blueApproaching starlight is compressed (blue--shifted).shifted).

�� Receding starlight is expanded (redReceding starlight is expanded (red--shifted).shifted).

No Doppler shift

This observer sees light waves “spread out” – red-shifted.

This observer sees light waves compressed – blue-shifted.

Fig. 1.5c

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The Expanding UniverseThe Expanding Universe

�� Light from galaxies was observed to be “redLight from galaxies was observed to be “red--shifted.” shifted.”

�� Edwin Hubble recognized the red shift as a Doppler effect. Edwin Hubble recognized the red shift as a Doppler effect.

��He concluded galaxies were moving away at great speed. He concluded galaxies were moving away at great speed.

��No galaxies were found heading toward Earth.No galaxies were found heading toward Earth.

�� Hubble deduced that the whole Universe mustHubble deduced that the whole Universe must

be expanding (analogous to raisin bread dough).be expanding (analogous to raisin bread dough).

��The expanding Universe theory. The expanding Universe theory.

��Did expansion start at some time in the past?Did expansion start at some time in the past?

��If so, how far back?If so, how far back?

��How small was the Universe before expansion?How small was the Universe before expansion?

Fig. 1.6a


Big BangBig Bang

�� An expanding Universe? “When did it all begin?”An expanding Universe? “When did it all begin?”

�� The Big Bang: all mass and energy in a single point.The Big Bang: all mass and energy in a single point.

�� It exploded ~13.7 Ga and has been expanding ever since.It exploded ~13.7 Ga and has been expanding ever since.

Fig. 1.6b


Aftermath of the Big BangAftermath of the Big Bang

�� Researchers have developed a model of the Big Bang. Researchers have developed a model of the Big Bang.

�� During the first instant, only energyDuring the first instant, only energy——no matterno matter——present.present.

�� Started as a rapid cascade of events.Started as a rapid cascade of events.

�� Hydrogen atoms within a few seconds.Hydrogen atoms within a few seconds.

�� At 3 minutes, hydrogen atoms fused to form helium atoms.At 3 minutes, hydrogen atoms fused to form helium atoms.

�� Light nuclei (Be, Li, B) by Big Bang nucleosynthesis. Light nuclei (Be, Li, B) by Big Bang nucleosynthesis.

�� The Universe expanded and cooled.The Universe expanded and cooled.

Fig. 1.6b

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After the Big BangAfter the Big Bang

�� With expansion and cooling, atoms began to bond. With expansion and cooling, atoms began to bond.

�� Hydrogen formed HHydrogen formed H22 moleculesmolecules——the fuel of stars.the fuel of stars.

�� Atoms and molecules coalesced into gaseous nebulae.Atoms and molecules coalesced into gaseous nebulae.

�� Gravity caused collapse of gaseous nebulae.Gravity caused collapse of gaseous nebulae.

�� Collapse resulted in increases in:Collapse resulted in increases in:

�� Temperature.Temperature.

�� Density.Density.

�� Rate of rotation.Rate of rotation.

Fig. 1.7


After the Big BangAfter the Big Bang

�� Mass in nebulae was not equally distributed. Mass in nebulae was not equally distributed.

�� An initially more massive region began to pull in gas.An initially more massive region began to pull in gas.

�� This region gained mass and density.This region gained mass and density.

�� Mass compacted into a smaller region and began to rotate.Mass compacted into a smaller region and began to rotate.

�� Rotation rate increased, developing a disk shapeRotation rate increased, developing a disk shape

�� The central ball of the disk became hot enough to glow.The central ball of the disk became hot enough to glow.

�� The first The first protostarprotostar is born is born -- 800 800 myrmyr after the Big Bang? after the Big Bang?

Geology at a Glance


Birth of the First StarsBirth of the First Stars

�� The protostar continued to grow.The protostar continued to grow.

�� Pulling in more mass and creating a denser core.Pulling in more mass and creating a denser core.

�� Temperatures soared to 10 million degrees.Temperatures soared to 10 million degrees.

�� At these temps, hydrogen nuclei fused to create helium. At these temps, hydrogen nuclei fused to create helium.

�� With the start of nuclear fusion, the protostar “ignited.”With the start of nuclear fusion, the protostar “ignited.”

Chapter 1 Opener

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Fig. 1.9

Birth of the First StarsBirth of the First Stars

�� First generation stars massive First generation stars massive –– x100 the mass of the x100 the mass of the Sun Sun

�� Large stars burn hotter and faster and exhaust HLarge stars burn hotter and faster and exhaust H22 fuel fuel rapidly. rapidly.

�� A huge star may only exist A huge star may only exist

for a few millions of years for a few millions of years

and then it explodes as a and then it explodes as a

SUPERNOVA to distributeSUPERNOVA to distribute

heavy elements into the heavy elements into the

adjacent universe. adjacent universe.


Where Do Elements Come From?Where Do Elements Come From?

�� Big Bang nucleosynthesis formed the lightest elements.Big Bang nucleosynthesis formed the lightest elements.

�� Atomic #s 1, 2, 3, 4, and 5 (H, He, Li, Be, and B).Atomic #s 1, 2, 3, 4, and 5 (H, He, Li, Be, and B).

�� Heavier elements are from stellar nucleosynthesis.Heavier elements are from stellar nucleosynthesis.

�� Atomic #s 6Atomic #s 6––26 (C to Fe).26 (C to Fe).

�� Elements with atomic #s >26 form during supernovae.Elements with atomic #s >26 form during supernovae.

Fig. 1.8


Where Do Elements Come From?Where Do Elements Come From?

�� First generation stars left a legacy of heavier elements.First generation stars left a legacy of heavier elements.

�� Second generation stars repeated heavy element Second generation stars repeated heavy element genesis.genesis.

�� Succeeding generations contain more heavy elements. Succeeding generations contain more heavy elements.

�� The Sun may be a third, fourth or fifth generation star.The Sun may be a third, fourth or fifth generation star.

�� The mix of elements found on Earth include:The mix of elements found on Earth include:

��Primordial gas from the Big Bang.Primordial gas from the Big Bang.

��The disgorged contents of exploded stars.The disgorged contents of exploded stars.

�� Elements ultimately originate in starsElements ultimately originate in stars

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�� The nebular theory of Solar System formation.The nebular theory of Solar System formation.

�� A third, fourth, or nth generation nebula forms 4.56 Ga. A third, fourth, or nth generation nebula forms 4.56 Ga.

�� Hydrogen and helium left over from the Big Bang.Hydrogen and helium left over from the Big Bang.

�� Heavier elements produced via:Heavier elements produced via:

��Stellar nucleosynthesis.Stellar nucleosynthesis.

��Supernovae.Supernovae.

�� The nebula condenses into a protoplanetary disk. The nebula condenses into a protoplanetary disk.

Nebular Theory of the Solar SystemNebular Theory of the Solar System

Geology at a Glance


�� The ball at the center grows dense and hot.The ball at the center grows dense and hot.

�� Fusion reactions begin; the Sun is born. Fusion reactions begin; the Sun is born.

�� Dust in the rings condenses into particles.Dust in the rings condenses into particles.

�� Particles coalesce Particles coalesce –– ACCRETE ACCRETE -- to form to form planetesimalsplanetesimals..

Solar System FormationSolar System Formation

Geology at a Glance


�� Such flattened rotating discs have been observed around Such flattened rotating discs have been observed around other stars.other stars.

�� Disc around star Beta Disc around star Beta PictorisPictoris::

Solar System FormationSolar System Formation

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Formation of the Solar SystemFormation of the Solar System

�� At any given location, the only materials to At any given location, the only materials to condense were those that could survive the condense were those that could survive the temperatures theretemperatures there

�� Only metallic grains could condense near the Only metallic grains could condense near the

protoproto--Sun in Mercury’s orbitSun in Mercury’s orbit

�� In contrast, gases could condense as lowIn contrast, gases could condense as low--density icy materials in the outer parts of the density icy materials in the outer parts of the embryonic Solar Systemembryonic Solar System

�� This accounts for the differences in the This accounts for the differences in the compositions of the planets compositions of the planets



Computer simulation of accretionComputer simulation of accretion

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Stellar wind sweeps dust and gas left Stellar wind sweeps dust and gas left over after star formationover after star formation


�� PlanetesimalsPlanetesimals clump into a lumpy clump into a lumpy protoplanetprotoplanet. .

�� Once >1000 km in diameter, interior is warm and soft Once >1000 km in diameter, interior is warm and soft enough to flow in response to gravity.enough to flow in response to gravity.

�� Protrusions pulled inward and Protrusions pulled inward and planetismalplanetismal becomes a becomes a sphere so gravity is the same at all points on its surfacesphere so gravity is the same at all points on its surface

Formation of planet EarthFormation of planet Earth

Geology at a Glance


Why are the rocky planets layered?Why are the rocky planets layered?

�� Random accretion, Random accretion, then heavier elements then heavier elements (Fe, Ni) sank to form a (Fe, Ni) sank to form a

core, with lighter core, with lighter silicate minerals left silicate minerals left over to form mantle over to form mantle OROR

�� Densest material Densest material accreted first to form accreted first to form protoproto--core, followed core, followed by lighter silicate by lighter silicate

materialmaterial

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Why are the rocky planets layered?Why are the rocky planets layered?


�� ~4.53 Ga, a Mars~4.53 Ga, a Mars--sized planetoid collides with Earth. sized planetoid collides with Earth.

�� The planet and a part of Earth mantle are disintegrated.The planet and a part of Earth mantle are disintegrated.

�� Collision debris forms a ring around the Earth.Collision debris forms a ring around the Earth.

�� The debris coalesces and forms the Moon. The debris coalesces and forms the Moon.

�� The Moon has a composition similar to Earth’s mantle. The Moon has a composition similar to Earth’s mantle.

Formation of the MoonFormation of the Moon

Geology at a Glance


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Earth Earth –– a unique planet in our Solar a unique planet in our Solar

System System �� An oxygenAn oxygen--rich rich

atmosphereatmosphere

�� Large amounts of Large amounts of water on its surfacewater on its surface

�� Hosts a wide variety Hosts a wide variety

of complex life formsof complex life forms

�� Its surface is Its surface is continuously continuously changing as a result changing as a result of PLATE TECTONICSof PLATE TECTONICS


�� Read Read MarshakMarshak Chapter 1Chapter 1

�� NASA Solar System ExplorationNASA Solar System Exploration

�� http://solarsystem.nasa.gov/index.cfmhttp://solarsystem.nasa.gov/index.cfm

�� NASA / JPL Solar System MissionsNASA / JPL Solar System Missions

�� http://www.jpl.nasa.gov/solarhttp://www.jpl.nasa.gov/solar--system/index.cfmsystem/index.cfm

�� BBC Big Bang Theory Program BBC Big Bang Theory Program

�� http://www.bbc.co.uk/science/space/universe/questions_and_ideas/big_http://www.bbc.co.uk/science/space/universe/questions_and_ideas/big_

bang/bang/

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