Post on 12-Jun-2018
transcript
Chapter 9pPlanetary Geology
Earth and the Other Terrestrial WorldsEarth and the Other Terrestrial Worlds
How doesThe EarthWork?Work?
What’s ourPast & Future?
COMPARATIVE PLANETOLOGY
G d
Past & Future?
Who are we?
HOMEGanymede
Where are we?Why is VenusWhy is VenusHot & Mars Cold?
To Answer: weCompare!
VenusMars
E th i Pl t f E t !Some aspects of our home planet are:Some aspects of our home planet are:
Earth is a Planet of Extremes!Molten interior generates Magnetic Field
Crack moving crust build Mountains,trigger Earthquakes & VolcanoesCrack moving crust build Mountains,trigger Earthquakes & VolcanoesTurbulent Atmosphere---- winds ,ice, water carve the land!
Earth is unique..it has water and life!
W t i i th t h l d iWater is in the atmosphere -> clouds -> rain
Water on landWater on land becomes rivers& ice that erodeth l dthe land on downhill trip to the Sea!
75% of the Earth is Liquid Water
Snapping crust along fault zones create Earthquakes and producevibrations (SEISMIC WAVES)that help us probe the Earth’s interior.
Earthquake effectsK b h 20 d h kKobe the 20 second earthquake
• Kobe earthquakeKobe earthquakeKobe 2
Kobe 3
Kobe dedication video…somewhat sad ..But not gory
Significant earthquakes 2010
Largest and deadliest earthquakes 1990-2010
Significant earthquakes 2010
9.1 Connecting Planetary Interiors and S fSurfaces
Our goals for learning:Our goals for learning:• What are terrestrial planets like on the
inside?inside?• What causes geological activity?• Why do some planetary interiors create
magnetic fields?
Seismic WavesSeismic Waves• VibrationsVibrations
that travel throughthrough Earth’s interior tellinterior tell us what Earth is likeEarth is like on the inside
Earth’s InteriorEarth s Interior• Core: HighestCore: Highest
density; nickel and iron
• Mantle:Moderate density; silicon, oxygen, etc.
• Crust: Lowest density; granite, b lt tbasalt, etc.
Terrestrial Planet InteriorsTerrestrial Planet Interiors
• Applying what we have learned about Earth’s interior to other planets tells us what their interiors are probably like
Four Stages toPlanetary Development
1. Melted Earth from Heat of Formation &Radioactivity gave usRadioactivity gave usDIFFERENTIATION
2 Hard crust formed2. Hard crust formed Rocky & icy debris of Solar Nebula gave us
But professor whereAre the signs of the Intense cratering on Earth?
CRATERINGIntense cratering on Earth?
3. Heat cracked crustWhy don’t we seelava flooded Deep & permitted lava &
Gases (H2O) to causeMassive FLOODING.
lava flooded Deep Basins on Earth?
Answer to both! Surface Massive FLOODING.Answer to both! Surface Changes!, Sliding crust pushes up Mountains,shifts continents Air &
4. SLOW SURFACEEVOLUTIONshifts continents, Air &
Water Erosion wear awayFeatures.
EVOLUTION1st billion years lost!
DifferentiationDifferentiation• Gravity pullsGravity pulls
high-density material to center
• Lower-density ymaterial rises to surface
• Material ends up separated by d itdensity
LithosphereLithosphere• A planet’s outerA planet s outer
layer of cool, rigid rock is gcalled the lithosphere
• It “floats” on the warmer, softer
k th t lirock that lies beneath
Strength of RockStrength of Rock• Rock stretches whenRock stretches when
pulled slowly but breaks when pulled prapidly
• The gravity of a large g y gworld pulls slowly on its rocky content, h i th ld i tshaping the world into
a sphere
Special Topic:How do we know what’s inside aHow do we know what s inside a
planet?• P waves
push matter back and forth
• S waves shake mattershake matter side to side
Special Topic:How do we know what’s inside aHow do we know what s inside a
planet?• P waves go
through Earth’s coreEarth s core but S waves do notdo not
• We concludeWe conclude that Earth’s core must have a liquid outer layer
Two Seismic Wave Types createdAt Earthquake area.A S i i i i l Vib iA Seismic wave is material Vibrating.P wave or Pressure waveVibration (back & forth) is along
Compressions( ) g
direction of motion. A compressiontravels in direction of motion (e.g. Sound)
S wave or Shear waveVibration (or displacement) is perpendicular to direction of motionp p
S waves travel slower than P wavesA d h h li id !And cannot get through liquids!
Seismograph = Earthquake detector…placed all over the earth.
NOTE TIME OF ARRIVAL!
Northern Canadian Seismograph recording of Mexican Earthquake.
Probing Earth’sInterior
Ch i D iChanging DensityCurves the pathOf the wave (we use the wordrefracts)
Note: S waveShadow.. &Three parts of pinteriorCrust MantleMantleCore (2 parts)
ThinThin Crust
Thought Question
What is necessary for differentiation to occur in a planet?
a) It must have metal and rock in itb) It must be a mix of materials of different density) M t i l i id t b bl t flc) Material inside must be able to flow
d) All of the abovee) b and ce) b and c
Thought Question
What is necessary for differentiation to occur in a planet?
a) It must have metal and rock in itb) It must be a mix of materials of different density) M t i l i id t b bl t flc) Material inside must be able to flow
d) All of the abovee) b and ce) b and c
Heating of InteriorHeating of Interior• Accretion andAccretion and
differentiation when planets pwere young
• Radioactive decay is most yimportant heat source today
Cooling of InteriorCooling of Interior• Convection
transports heat as hot material rises and coolrises and cool material falls
• ConductionConductiontransfers heat from hot
t i l t lmaterial to cool material
• Radiation• Radiationsends energy into space
Role of SizeRole of Size
• Smaller worlds cool off faster and harden earlier
• Moon and Mercury are now geologically “dead”
Surface Area to Volume RatioSurface Area to Volume Ratio• Heat content depends on volume• Loss of heat through radiation depends on
surface areaf• Time to cool depends on surface area divided
by volume
surface area to volume ratio = 4r2
43r3
3r
3
• Larger objects have smaller ratio and cool more l l T f h l l !slowly. True for whales also!
MagnetismPlays a Major Role
On the structure of theOn the structure of the Sun
and important on EarthHere Iron filings are
Sprinkled about aMagnet andMagnet and
We get a sense of whatIs happening
Around the space ofAround the space ofThe magnet
FILM: MAGNETAND IRON FILINGS
FILM 3D FIELD
Sources of Magnetic FieldsSources of Magnetic Fields
• Motions of charged particles are whatparticles are what create magnetic fields
• In Planets and the Sun!
Sources of Magnetic FieldsSources of Magnetic Fields• A planet canA planet can
have a magnetic field if charged gparticles are moving inside
• 3 requirements:– Molten interior– Convection– Moderately
id t tirapid rotation
SHIELDS UP!SOLAR WIND IS COMING!
Earth’s MAGNETIC FIELD
Earth rotatesRising heatC tiCauses convectionIn liquid core.
Which is aWhich is aHighly electricallyconductiveIron-nickel alloy
DYNAMO EFFECTDYNAMO EFFECT=rotation of convectingconducting liquidgenerates thedipole magnetic field
YEP IT REALLY IS A SHIELDWithout which we all die!
Deflectingsurfacesurface
P ti l l k d
Area dominated byEarth Magnetic field
Particles leaked In from theSolar wind Earth Magnetic fieldGet trapped( Van Allen radiation belts)radiation belts)
AURORA
Solar wind particlesThat leak into the Earth’s upper AtmosphereIonize gas atoms thatIonize gas atoms thatCapture electronsResulting in AAn EMISSION SPECTRUMOf rays& beautifulcurtainscurtains
COSMIC NEONCOSMIC NEONCOSMIC NEON
Another Aurora (Polar Light)
As high-energy particles leak into the lowerAs high energy particles leak into the lower magnetosphere, they excite molecules near the
Earth’s magnetic poles, causing the aurora
9.2 Shaping Planetary Surfaces9.2 Shaping Planetary Surfaces
Our goals for learning:Our goals for learning:• What processes shape planetary
surfaces?surfaces?• Why do the terrestrial planets have
diff t l i l hi t i ?different geological histories?• How do impact craters reveal a surface’s
geological age?
Processes that Shape Surfaces
• Impact crateringImpact cratering– Impacts by asteroids or comets
• VolcanismVolcanism– Eruption of molten rock onto surface
• TectonicsTectonics– Disruption of a planet’s surface by internal
stresses• Erosion
– Surface changes made by wind, water, or Su ace c a ges ade by d, ate , oice
Impact CrateringImpact Cratering• Most crateringMost cratering
happened soon after solar system formedy
• Craters are about 10 times wider than object that made them
• Small craters greatly outnumber large ones
Impact Cratersmore details when we study Asteroidsmore details when we study Asteroids
and Comets that cause them.
Meteor Crater (Arizona)Meteor Crater (Arizona) Tycho (Moon)Tycho (Moon)
Impact Craters on MarsImpact Craters on Mars
“standard” crater“standard” crater impact into icy groundimpact into icy ground eroded cratereroded crater
VolcanismVolcanism• Volcanism happensVolcanism happens
when molten rock (magma) finds a ( g )path through lithosphere to the
fsurface• Molten rock is called
l ft it hlava after it reaches the surface
Lava and VolcanoesLava and Volcanoes
Runny lava makes flat Runny lava makes flat lava plainslava plains
Slightly thicker lava Slightly thicker lava makes broad makes broad shield shield
Thickest lava makes Thickest lava makes steep steep stratovolcanoesstratovolcanoes
volcanoesvolcanoes
How to see a volcano?G t l tGet some crazy people to Join you and head forCosta Rica or HawaiiBE CAREFUL!
•• Small Volcano eruptionSmall Volcano eruption <-Small Volcano erupts
ARENAL& STRANGEPERSON
-Click Here
PERSONIN JUNGLE
TectonicsTectonics
• Convection of the mantle creates stresses in the crust called tectonic forcesthe crust called tectonic forces
• Compression forces make mountain ranges• Valley can form where crust is pulled aparty p p
AppalachianMountainsFrom spaceFrom space.
A FOLDEDMOUTAINCHAIN
Tell taleTell taleSign ofPlateT iTectonics
Plate Tectonics on EarthPlate Tectonics on Earth• Earth’sEarth s
continents slide around on separate plates of crust
ErosionErosion• Erosion is a blanket term for weather-
driven processes that break down or transport rock
• Processes that cause erosion include– Glaciers– Rivers– WindWind
Erosional DebrisErosional Debris
• Erosion can create new features byfeatures by depositing debrisdebris
Result of Uplift and Erosion of Sedimentary Rock
How did a fossil fish get in the rocks on top of a pMountain??