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!

EARLY HEAVY BOMBARDMENT YOUNG EARTH & MOON

GLOWING BY THE HEAT OF ACCRETION!

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?

What are terrestrial planets like on the inside?

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

What causes geological activity?

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!

Why do some planetary interiors create magneticinteriors create magnetic

fields?

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

Aurora are dynamic!• Aurora Australis From McMurdo station Antarctica

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?

What processes shape planetary surfaces?

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

OutgassingOutgassing

• Volcanism also releases gases from Earth’s interior into atmosphere

Cinder Cones volcanoes of ash ..not permanent e.g. disappearing Islands

Lava solidifies volcano as it hardens

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

Mt. St. HelensWashington

Mt. St. Helens debris avalanche

Volcanic Island chains like ?

Volcanic Plugs

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

Note: linear Mountain rangePLATE TECTONICS

Hawaii

Chilean Andes

Deep Trenchp

AppalachianMountainsFrom spaceFrom space.

A FOLDEDMOUTAINCHAIN

Tell taleTell taleSign ofPlateT iTectonics

Bhagirathi Himalayas

PLATE TECTONICS

LITHOSPHERE

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

Erosion by WaterErosion by Water

• Colorado River continues tocontinues to carve Grand CanyonCanyon

Water erodes and carries sediments

Erosional DebrisErosional Debris

• Erosion can create new features byfeatures by depositing debrisdebris

Sediments

Buried deepBuried deep

Become

Rock

Result of Uplift and Erosion of Sedimentary Rock

How did a fossil fish get in the rocks on top of a pMountain??

Water, Wind& IceErode theErode theLand

DendriticStream patternDrainage ofhighlandshighlands

Yemen

NileDelta

Meandering old river in its FLOOD PLAIN!

Erosion by IceErosion by Ice

• Glaciers carved the YosemiteYosemite Valley

ICE Mountain Glaciers pulled by gravity erode the land

Glacier melts at its foot but is still traveling slowly downhill!

Glaciers transport the rocks of the land and mountains

Glaciers can drop this material and build a moraine. Grymes hill!

During A glacial retreat ERRATICS are dropped from many miles away!

Mountain glaciers sharpen ridges creating horns & aretes

Glaciated U valley and rounded hills after a retreat..also fiords near water

Fiord

Sea Ice in the North Ice cap

I B bi Rh d I l dIce Berg as big as Rhode Island

Antarctica Ice Cap

Erosion by WindErosion by Wind

• Wind wears away rock and builds up sandbuilds up sand dunes

What’s going on down there?