Chapter 7 Earth and the Terrestrial Worlds

Chapter 7Chapter 7Earth and the Terrestrial Earth and the Terrestrial

WorldsWorlds

WHAT DO YOU THINK?

1. Why are Venus (too HOT), Mars (too COLD) and Earth (just right!) so different in their atmospheres?

2. Could Mars have supported life long ago? How do we know?

3. Is life known to exist on Mars today?

Final Exam Essay Question Final Exam Essay Question

Describe the atmospheres of Venus, Earth, and Mars. Why are these three atmospheres so different?

MercuryMercury

craterscraterssmooth plainssmooth plains

cliffscliffs

VenusVenus

volcanoesvolcanoesfew cratersfew craters

Radar view of a twin-peaked volcano

MarsMars

some craterssome cratersvolcanoesvolcanoesriverbeds?riverbeds?

MoonMoon

craterscraterssmooth plainssmooth plains

EarthEarth

volcanoesvolcanoescraterscraters

mountainsmountainsriverbedsriverbeds

Why have the planets turned Why have the planets turned out so differently, even though out so differently, even though they formed at the same time they formed at the same time from the same materialsfrom the same materials??

Goals: Understanding Earth Goals: Understanding Earth as a Planetas a Planet

Why is Earth geologically active?Why is Earth geologically active?

What processes shape Earth’s surface?What processes shape Earth’s surface?

How does Earth’s atmosphere affect the How does Earth’s atmosphere affect the planet?planet?

Why is Earth geologically Why is Earth geologically active?active?

Earth’s InteriorEarth’s InteriorCoreCore::

HighestHighest density; nickel density; nickel & iron& iron

MantleMantle:: ModerateModerate density; density; silicon, oxygen, silicon, oxygen, etc.etc.

CrustCrust:: LowestLowest density; density; granite, basalt, etc.granite, basalt, etc.

Terrestrial Planet InteriorsTerrestrial Planet Interiors

Applying what we learn about Earth’s Applying what we learn about Earth’s interior to other planets tells us what their interior to other planets tells us what their interiors are interiors are probablyprobably like. like.

Why do water and oil separate?Why do water and oil separate?

A.A. Water molecules repel oil molecules Water molecules repel oil molecules electrically.electrically.

B.B. Water is denser than oil, so oil floats Water is denser than oil, so oil floats on water.on water.

C.C. Oil is more slippery than water, so it Oil is more slippery than water, so it slides to the surface of the water.slides to the surface of the water.

D.D. Oil molecules are bigger than the Oil molecules are bigger than the spaces between water molecules.spaces between water molecules.

Why do water and oil separate?Why do water and oil separate?

A.A. Water molecules repel oil molecules Water molecules repel oil molecules electrically.electrically.

B.B. Water is denser than oil, so oil Water is denser than oil, so oil floats on water.floats on water.

C.C. Oil is more slippery than water, so it Oil is more slippery than water, so it slides to the surface of the water.slides to the surface of the water.

D.D. Oil molecules are bigger than the Oil molecules are bigger than the spaces between water molecules.spaces between water molecules.

DifferentiationDifferentiationGravity pulls high-Gravity pulls high-

density material to density material to centercenter

Lower-density Lower-density material rises to material rises to surfacesurface

Material ends up Material ends up separated by separated by densitydensity

Thought QuestionThought Question

What is necessary for What is necessary for differentiation to occur in a to occur in a planet?planet?

A.A. It must have metal andIt must have metal and rock in it.rock in it.B.B. It must be a mix of materials of different It must be a mix of materials of different

density.density.C.C. Material inside must be able to flow.Material inside must be able to flow.D.D. All of the above.All of the above.E.E. b and c.b and c.


What is necessary for What is necessary for differentiation differentiation to occur in a to occur in a planet?planet?

A. It must have metal and rock in it.B. It must be a mix of materials of different

density.C. Material inside must be able to flow.D. All of the above.

E. b and c!

LithosphereLithosphere

A planet’s outer A planet’s outer layer of cool, layer of cool, rigid rockrigid rock

Lithosphere Lithosphere “floats” on “floats” on warmer, softer warmer, softer rock beneath.rock beneath.


Do rocks Do rocks s-t-r-e-t-c-h??

A.A. No—rock is rigid and cannot deform No—rock is rigid and cannot deform without breaking.without breaking.

B.B. Yes—but only if it is molten rock.Yes—but only if it is molten rock.C.C. Yes—rock under strain may slowly Yes—rock under strain may slowly

deform.deform.


Do rocks s-t-r-e-t-c-h?Do rocks s-t-r-e-t-c-h?

A.A. No—rock is rigid and cannot deform No—rock is rigid and cannot deform without breaking.without breaking.

B.B. Yes—but only if it is molten rock.Yes—but only if it is molten rock.C. Yes—rock under strain may slowly

deform.

Strength of RockStrength of RockRock stretches when Rock stretches when

pulled slowly but pulled slowly but breaks when pulled breaks when pulled rapidly.rapidly.

The The gravitygravity of a large of a large world pulls slowly on world pulls slowly on its rocky content, its rocky content, shaping the world into shaping the world into a sphere.a sphere.

Heat Drives Geological ActivityHeat Drives Geological Activity

ConvectionConvection: hot rock : hot rock rises, cool rock falls.rises, cool rock falls.

One convection cycle One convection cycle takes ~100 million takes ~100 million years on Earth.years on Earth.

Sources of Internal HeatSources of Internal Heat

1.1. AccretionAccretion releases releases gravitational gravitational potential energy potential energy

2.2. DifferentiationDifferentiation

3.3. RadioactivityRadioactivity

Heating of Interior over TimeHeating of Interior over TimeAccretionAccretion and and

differentiationdifferentiation when planets when planets were youngwere young

Radioactive Radioactive decay decay is most is most important heat important heat source todaysource today

Cooling of InteriorCooling of Interior

Convection

Conduction

Radiation

Cooling of InteriorCooling of Interior Convection transports transports

heat as hot material rises heat as hot material rises and cool material fallsand cool material falls

ConductionConduction transfers transfers heat from hot material to heat from hot material to cool materialcool material

RadiationRadiation sends energy sends energy into spaceinto space


What cools off fasterWhat cools off faster??

A.A. A grande-size cup of Starbucks coffeeA grande-size cup of Starbucks coffee

B.B. A teaspoon of cappuccino in the same A teaspoon of cappuccino in the same cupcup


What cools off faster?What cools off faster?

A.A. A grande-size cup of Starbucks coffeeA grande-size cup of Starbucks coffee

B.B. A teaspoon of cappuccino in the same A teaspoon of cappuccino in the same cupcup



A.A. A big terrestrial planetA big terrestrial planet

B.B. A tiny terrestrial planetA tiny terrestrial planet



A.A. A big terrestrial planetA big terrestrial planet

B.B. A tiny terrestrial planetA tiny terrestrial planet

Brrrr!

Role of SizeRole of Size

SmallerSmaller worlds worlds coolcool off off fasterfaster and harden earlier and harden earlier

Moon and Mercury are now geologically “dead”Moon and Mercury are now geologically “dead”

Surface Area to Volume RatioSurface Area to Volume Ratio

Heat content depends on volume.Heat content depends on volume.

Loss of heat through radiation depends on surface area.Loss of heat through radiation depends on surface area.

Time to cool depends on surface area divided by volume:Time to cool depends on surface area divided by volume:

surface area to volume ratio = 4r2

43r3

3r

Larger objects have a smaller ratio and cool Larger objects have a smaller ratio and cool more slowly.more slowly.

Planetary Magnetic FieldsPlanetary Magnetic Fields

Moving charged particles create magnetic fields.Moving charged particles create magnetic fields.

A planet’s interior can create magnetic fields if - it is electrically conducting, &- it is circulating and/or rotating.

Earth’s MagnetosphereEarth’s Magnetosphere

Earth’s magnetic fields protects us from Earth’s magnetic fields protects us from charged particles from the Sun.charged particles from the Sun.

The charged particles can create aurorae The charged particles can create aurorae (“Northern lights”).(“Northern lights”).


If the planet core is cold, do you expect it to have If the planet core is cold, do you expect it to have magnetic fields?magnetic fields?

A.A. YesYes, refrigerator magnets are cold, and they , refrigerator magnets are cold, and they have magnetic fields.have magnetic fields.

B.B. NoNo, planetary magnetic fields are generated , planetary magnetic fields are generated by moving charges around, and if the core is by moving charges around, and if the core is cold, nothing is moving.cold, nothing is moving.

Thought QuestionThought QuestionIf the planet core is cold, do you expect it to have If the planet core is cold, do you expect it to have magnetic fields?magnetic fields?

A.A. Yes, refrigerator magnets are cold, and they have Yes, refrigerator magnets are cold, and they have magnetic fields.magnetic fields.

B. No, planetary magnetic fields are generated by moving charges around, and if the core is cold, nothing is moving.

How do we know what’s How do we know what’s insideinside a planet? a planet?

““PP” waves ” waves ppush matter ush matter back and back and forth.forth.

““SS” waves ” waves sshake matter hake matter sside to ide to sside.ide.

How do we know what’s inside a planet?How do we know what’s inside a planet?

PP waves go waves go through Earth’s through Earth’s core, but core, but SS waves do not.waves do not.

Earth’s core Earth’s core must have a must have a liquid outer layer.liquid outer layer.

What processes shape Earth’s What processes shape Earth’s surface?surface?

Geological ProcessesGeological Processes Impact cratering

— Impacts by asteroids or cometsImpacts by asteroids or cometsVolcanism

— Eruption of molten rock onto surfaceEruption of molten rock onto surfaceTectonics

— Disruption of surface by internal stressesDisruption of surface by internal stressesErosion

— Changes made by wind, water, or iceChanges made by wind, water, or ice

Impact CrateringImpact Cratering Most cratering happened Most cratering happened

soon after solar system soon after solar system formed.formed.

Craters about 10 times Craters about 10 times wider than objects that wider than objects that made them.made them.

Small craters greatly Small craters greatly outnumber large ones.outnumber large ones.

Impact CratersImpact Craters

Meteor Crater (Arizona)Meteor Crater (Arizona) Tycho (Moon)Tycho (Moon)

VolcanismVolcanism Molten rock Molten rock

((magmamagma) finds path ) finds path through lithosphere through lithosphere to surface.to surface.

Molten rock is Molten rock is called called lavalava after it after it reaches the reaches the surface.surface.

Lava and VolcanoesLava and Volcanoes

Runny lava makes flat Runny lava makes flat lava plains.lava plains.

Slightly thicker lava Slightly thicker lava makes broad makes broad shield shield volcanoes.volcanoes.

Thickest lava makes Thickest lava makes steep steep stratovolcanoes.stratovolcanoes.

OutgassingOutgassingNo, not from cows…No, not from cows…

OutgassingOutgassing

Volcanism also releases gases from Earth’s Volcanism also releases gases from Earth’s interior into the atmosphere.interior into the atmosphere.

TectonicsTectonics

Convection of the mantle creates stresses in the crust Convection of the mantle creates stresses in the crust called called tectonic forcestectonic forces..

Compression forces make mountain ranges.Compression forces make mountain ranges. A valley can form where the crust is pulled apart.A valley can form where the crust is pulled apart.

ErosionErosionWeather-driven processes that break Weather-driven processes that break

down or transport rock.down or transport rock.

Processes includeProcesses include

— Water/Ice movementWater/Ice movement by glaciers & rivers by glaciers & rivers— Atmospheric MovementAtmospheric Movement by wind, storms by wind, storms— Cyclic Cyclic heating/coolingheating/cooling

Erosion by WaterErosion by Water

The Colorado The Colorado River continues River continues to carve the to carve the Grand Canyon.Grand Canyon.

Erosion by IceErosion by Ice

Glaciers Glaciers carved the carved the Yosemite Yosemite Valley.Valley.

Erosion by WindErosion by Wind

Wind wears Wind wears away rock and away rock and builds up sand builds up sand dunes.dunes.

Erosional DebrisErosional Debris

Erosion can Erosion can create new create new features by features by depositing depositing debris.debris.

How does Earth’s atmosphere How does Earth’s atmosphere affect the planet ?affect the planet ?

Effects of Atmosphere on EarthEffects of Atmosphere on Earth

1.1. ErosionErosion

2.2. Makes the sky blue! Makes the sky blue!

3.3. Radiation protectionRadiation protection

4.4. Greenhouse effectGreenhouse effect


Why is the sky blue?Why is the sky blue?

A.A. The sky reflects light from the oceans.The sky reflects light from the oceans.

B.B. Oxygen atoms are blue.Oxygen atoms are blue.

C.C. Nitrogen atoms are blue.Nitrogen atoms are blue.

D.D. Air molecules scatter blue light more than Air molecules scatter blue light more than red light.red light.

E.E. Air molecules absorb red light.Air molecules absorb red light.


Why is the sky blue?Why is the sky blue?

A.A. The sky reflects light from the oceans.The sky reflects light from the oceans.

B.B. Oxygen atoms are blue.Oxygen atoms are blue.

C.C. Nitrogen atoms are blue.Nitrogen atoms are blue.

D. Air molecules scatter blue light more than red light.

E.E. Air molecules absorb red light.Air molecules absorb red light.

Why the sky is blueWhy the sky is blue Atmosphere scatters Atmosphere scatters

blue light from the blue light from the Sun, making it Sun, making it appear to come from appear to come from different directions.different directions.

Sunsets are red Sunsets are red because less of the because less of the red light from the Sun red light from the Sun is scattered.is scattered.

Earth’s atmosphere absorbs light at most wavelengths.

Radiation ProtectionRadiation Protection

All X-ray light is All X-ray light is absorbed very high in absorbed very high in the atmosphere.the atmosphere.

Ultraviolet light is Ultraviolet light is absorbed by ozone absorbed by ozone (O(O33) ~ 30 miles high) ~ 30 miles high

The Greenhouse EffectThe Greenhouse Effect

The Greenhouse Effect on The Greenhouse Effect on EarthEarth

Greenhouse effect:

Certain molecules let sunlight through but trap escaping infrared photons.

(H2O, CO2, CH4)

Greenhouse GasesGreenhouse Gases Any gas that Any gas that absorbs infrared

Greenhouse gas: often molecules with two Greenhouse gas: often molecules with two different types of elements (COdifferent types of elements (CO22, H, H22O, CHO, CH44))

Not a greenhouse gas: molecules with one or Not a greenhouse gas: molecules with one or two atoms of the same element (Otwo atoms of the same element (O22, N, N22))

Greenhouse Effect: Bad?Greenhouse Effect: Bad?

The Earth is much warmer because of the The Earth is much warmer because of the greenhouse effect than it would be without greenhouse effect than it would be without an atmosphere…but so is Venus.an atmosphere…but so is Venus.

Why is Venus too hot, Mars Why is Venus too hot, Mars too cold, and Earth just right??too cold, and Earth just right??

The The GoldilocksGoldilocks Question! Question!

Why is Venus too hot, Mars too cold, and Why is Venus too hot, Mars too cold, and Earth just right??Earth just right??

The Goldilocks Question!The Goldilocks Question!

• Distance? • Venus is too close, Mars too far away

from the Sun, and Earth just right?• Size?

• Mars too small to retain its heat?• Life?

• Earth’s oceans and life forms tranform the planet?

The Role of The Role of DistanceDistance??

Earth is located at an optimal distance Earth is located at an optimal distance from the Sun for liquid water to exist…from the Sun for liquid water to exist…

DistanceDistance can’t be the only factor! can’t be the only factor!

We now know MARS had liquid water, We now know MARS had liquid water, too!too!

The Role of The Role of SIZESIZE??

Earth is large enough for internal heat to Earth is large enough for internal heat to drive volcanoes and create an drive volcanoes and create an

atmosphereatmosphere

SIZESIZE can’t be the only factor! can’t be the only factor!

Earth and Venus are almost the same Earth and Venus are almost the same size, and seem identical in composition!size, and seem identical in composition!

The Role of The Role of AtmosphereAtmosphere??

Earth is able to recycle CO2 and retain Earth is able to recycle CO2 and retain water in its atmosphere…water in its atmosphere…

A Combination of Factors…A Combination of Factors…Earth is habitable because it is:

large enough to remain geologically active, at the right distance from Sun so oceans could form, AND

able to retain water in the atmosphere to help cycle CO2

The Greenhouse EffectThe Greenhouse Effect

Greenhouse GasesGreenhouse Gases Any gas that Any gas that absorbs infrared light

Greenhouse gas: Greenhouse gas: often molecules with two often molecules with two different types of elements (COdifferent types of elements (CO22, H, H22O, CHO, CH44))

Not a greenhouse gas: Not a greenhouse gas: molecules with one or molecules with one or two atoms of the same element (Otwo atoms of the same element (O22, N, N22))

The Greenhouse Effect on The Greenhouse Effect on EarthEarth

Greenhouse Effect: Bad?Greenhouse Effect: Bad?

The Earth is much warmer because of the greenhouse effect The Earth is much warmer because of the greenhouse effect than it would be without an atmosphere…but so is Venus.than it would be without an atmosphere…but so is Venus.

How can Earth “regulate” COHow can Earth “regulate” CO22??

Goldilocks & the Earth’s Goldilocks & the Earth’s CO2 cycle CO2 cycle

What does COKE have to do with What does COKE have to do with Astronomy??Astronomy??


Carbonation was Carbonation was notnot initially part of Coke! initially part of Coke!


Carbonation occurs naturally when pushing Carbonation occurs naturally when pushing water with CO2 gas!water with CO2 gas!

Carbon Dioxide CycleCarbon Dioxide Cycle• How does our

atmosphere & tectonics combine to regulate temperatures?

• How does life play a role?

Carbon Dioxide CycleCarbon Dioxide CycleStep 1: Evaporation/Rain

• Liquid water evaporatesLiquid water evaporates

• Condenses into clouds Condenses into clouds in lower atmospherein lower atmosphere

• Rain falls through Rain falls through atmosphere forming atmosphere forming Carbonic Acid (HCarbonic Acid (H22COCO3)3)

CO2 gas is absorbedCO2 gas is absorbed

1

Carbon Dioxide CycleCarbon Dioxide CycleStep 2: Mineral Erosion by Acid Rain

• Carbonic Acid (HCarbonic Acid (H22COCO33) in ) in rivers erodes rocksrivers erodes rocks

• Carbonate (COCarbonate (CO332-2-) ion ) ion

picked up in minerals picked up in minerals washed to oceanwashed to ocean

• Calcium easily absorbedCalcium easily absorbed

CO2 is carried to oceansCO2 is carried to oceans

2

Carbon Dioxide CycleCarbon Dioxide CycleStep 3: Tying Carbon into Rocks &

Life!• Calcium from rocks Calcium from rocks

forms CaCOforms CaCO33 (Calcium (Calcium Carbonate)Carbonate)

• CaCOCaCO33 = Limestone = Limestone

• CaCOCaCO33 = Coral, Mollusk = Coral, Mollusk shells!shells!

3

CO2 accumulates on CO2 accumulates on seafloorseafloor

Carbon Dioxide CycleCarbon Dioxide CycleStep 4: Tectonics & Subduction!

• Tectonics gradually pulls Tectonics gradually pulls seafloor downseafloor down

• CaCOCaCO33 broken back into broken back into CO2 & other mineralsCO2 & other minerals

4 CO2 now inside crustCO2 now inside crust

Carbon Dioxide CycleCarbon Dioxide CycleStep 5: Volcanic Outgassing!

• Eventual Volcanic Eventual Volcanic Activity pushes CO2 Activity pushes CO2 back into atmosphereback into atmosphere

5 CO2 now in CO2 now in atmosphere again!atmosphere again!

Carbon Dioxide CycleCarbon Dioxide Cycle• “Recycle” CO2

from atmosphere to crust to atmosphere over time

• Estimate ~25 million years or more for this to occur globally

Carbon Dioxide Cycle Carbon Dioxide Cycle “Feedback Loop”“Feedback Loop”

Suppose evaporation stopped, during an ice age….

What would happen over time?

Carbon Dioxide CycleCarbon Dioxide CycleFeedback Loop: Ice Age

• No evaporationNo evaporation• No RainNo Rain• NO NO CO2 gas absorbedCO2 gas absorbed1


• No evaporationNo evaporation• No RainNo Rain• NO NO CO2 gas absorbedCO2 gas absorbedBut…But…• Tectonic Activity & Tectonic Activity &

Volcanoes continue!Volcanoes continue!• Gradual CO2 Gradual CO2

concentration increase!concentration increase!

15


• Tectonic Activity & Volcanoes continue!

• Gradual CO2 concentration increase!

• More Greenhouse Effect => warmer!

• Ice Melts!• Cycle restored!

15

Long-Term Climate ChangeLong-Term Climate Change

Changes in Earth’s axis tilt might lead to Changes in Earth’s axis tilt might lead to ice ages.ice ages.

Widespread ice tends to lower global Widespread ice tends to lower global temperatures by increasing Earth’s temperatures by increasing Earth’s reflectivity.reflectivity.


CO2 from outgassing will build up if oceans are frozen, ultimately raising global temperatures

again.


Suppose CO2 in our atmosphere traps too much heat, and we heat up?


Carbon Dioxide CycleCarbon Dioxide CycleFeedback Loop: Global Warming

• Liquid water Liquid water evaporates FASTERevaporates FASTER

• MORE RainMORE Rain

MORE CO2 gas is MORE CO2 gas is absorbedabsorbed

15


• Volcanoes continue at “normal” rate…

• Gradual CO2 concentration decrease!

• Less Greenhouse Effect => cooler!

• Cycle restored!

51

Earth as a “Earth as a “LivingLiving” Planet” PlanetWhat unique features on Earth are What unique features on Earth are

important for human life?important for human life?

How is human activity changing our How is human activity changing our planet?planet?

What makes a planet habitable?What makes a planet habitable?

What unique features of Earth What unique features of Earth are important for life?are important for life?

1.1. Surface liquid waterSurface liquid water2.2. Atmospheric oxygenAtmospheric oxygen3.3. Plate tectonicsPlate tectonics4.4. Climate stabilityClimate stability

What unique features of Earth What unique features of Earth are important to human life?are important to human life?

1.1. Surface liquid waterSurface liquid water2.2. Atmospheric oxygenAtmospheric oxygen3. Plate tectonics4. Climate stability

Earth’s distance from the Sun and

moderate greenhouse effect make liquid water possible.



PHOTOSYNTHESIS (plant life) is required to make

high concentrations of O2, which also produces the

protective layer of O3.



Plate tectonics are an

important step in the

carbon dioxide cycle.

Continental MotionContinental Motion Idea of Idea of

continental drift continental drift was inspired by was inspired by puzzle-like fit of puzzle-like fit of continentscontinents

Mantle material Mantle material erupts where erupts where seafloor spreadsseafloor spreads

Plate MotionsPlate Motions

Continental MotionContinental Motion

Motion of continents can be Motion of continents can be measured with GPSmeasured with GPS

Tectonics & Seafloor RecyclingTectonics & Seafloor Recycling

Seafloor is recycled through a process Seafloor is recycled through a process known as subductionknown as subduction

Carbon Dioxide CycleCarbon Dioxide Cycle• How does our

atmosphere & tectonics combine to regulate temperatures?

• How does life play a role?

Carbon Dioxide CycleCarbon Dioxide CycleStep 1: Evaporation/Rain

• Liquid water evaporatesLiquid water evaporates

• Condenses into clouds Condenses into clouds in lower atmospherein lower atmosphere

• Rain falls through Rain falls through atmosphere forming atmosphere forming Carbonic Acid (HCarbonic Acid (H22COCO3)3)

CO2 gas is absorbedCO2 gas is absorbed

1

Carbon Dioxide CycleCarbon Dioxide CycleStep 2: Mineral Erosion by Acid Rain

• Carbonic Acid (HCarbonic Acid (H22COCO3) 3) in in rivers erodes rocksrivers erodes rocks

• Carbonate (COCarbonate (CO332-2-) ion ) ion

picked up in minerals picked up in minerals washed to oceanwashed to ocean

• Calcium easily absorbedCalcium easily absorbed

CO2 is carried to oceansCO2 is carried to oceans

2

Carbon Dioxide CycleCarbon Dioxide CycleStep 3: Tying Carbon into Rocks &

Life!• Calcium from rocks Calcium from rocks

forms CaCOforms CaCO33 (Calcium (Calcium Carbonate)Carbonate)

• CaCOCaCO33 = Limestone = Limestone

• CaCOCaCO33 = Coral, Mollusk = Coral, Mollusk shells!shells!

3

CO2 accumulates on CO2 accumulates on seafloorseafloor

Carbon Dioxide CycleCarbon Dioxide CycleStep 4: Tectonics & Subduction!

• Tectonics gradually pulls Tectonics gradually pulls seafloor downseafloor down

• CaCOCaCO33 broken back into broken back into CO2 & other mineralsCO2 & other minerals

4 CO2 now inside crustCO2 now inside crust

Carbon Dioxide CycleCarbon Dioxide CycleStep 5: Volcanic Outgassing!

• Eventual Volcanic Eventual Volcanic Activity pushes CO2 Activity pushes CO2 back into atmosphereback into atmosphere

5 CO2 now in CO2 now in atmosphere again!atmosphere again!

Carbon Dioxide CycleCarbon Dioxide Cycle• “Recycle” CO2

from atmosphere to crust to atmosphere over time

• Estimate ~25 million years or more for this to occur globally


Suppose evaporation stopped, during an ice age….



• No evaporationNo evaporation• No RainNo Rain• NO NO CO2 gas absorbedCO2 gas absorbed1


• No evaporationNo evaporation• No RainNo Rain• NO NO CO2 gas absorbedCO2 gas absorbedBut…But…• Tectonic Activity & Tectonic Activity &

Volcanoes continue!Volcanoes continue!• Gradual CO2 Gradual CO2

concentration increase!concentration increase!

15


• Tectonic Activity & Volcanoes continue!

• Gradual CO2 concentration increase!

• More Greenhouse Effect => warmer!

• Ice Melts!• Cycle restored!

15


Changes in Earth’s axis tilt might lead to Changes in Earth’s axis tilt might lead to ice ages.ice ages.

Widespread ice tends to lower global Widespread ice tends to lower global temperatures by increasing Earth’s temperatures by increasing Earth’s reflectivity.reflectivity.


CO2 from outgassing will build up if oceans are frozen, ultimately raising global temperatures

again.


Suppose CO2 in our atmosphere traps too much heat, and we heat up?



• Liquid water Liquid water evaporates FASTERevaporates FASTER

• MORE RainMORE Rain

MORE CO2 gas is MORE CO2 gas is absorbedabsorbed

15


• Volcanoes continue at “normal” rate…

• Gradual CO2 concentration decrease!

• Less Greenhouse Effect => cooler!

• Cycle restored!

51


1.1. Surface liquid waterSurface liquid water2.2. Atmospheric oxygenAtmospheric oxygen3.3. Plate tectonicsPlate tectonics4.4. Climate stabilityClimate stability The CO2 cycle acts

like a thermostat for Earth’s temperature.

These unique features are intertwined:These unique features are intertwined:

• Plate tectonicsPlate tectonics create create climate stabilityclimate stability• Climate stabilityClimate stability allows allows liquid waterliquid water• Liquid waterLiquid water is necessary for is necessary for lifelife• LifeLife is necessary for atmospheric is necessary for atmospheric

oxygenoxygen

How many other connections between these can you think of?

How is human activity changing our planet?

Dangers of Human ActivityDangers of Human Activity Human-made CFCs in the atmosphere destroy Human-made CFCs in the atmosphere destroy

ozone, reducing protection from UV radiation.ozone, reducing protection from UV radiation.

Human activity is driving many other species to Human activity is driving many other species to extinction.extinction.

Human use of fossil fuels produces Human use of fossil fuels produces greenhouse gases that can cause global greenhouse gases that can cause global warming.warming.

Global Climate ChangeGlobal Climate ChangeEarth’s average temperature has Earth’s average temperature has

increased by 0.5°C in the past 50 years.increased by 0.5°C in the past 50 years.

The concentration of COThe concentration of CO2 2 is rising rapidly.is rising rapidly.

An unchecked rise in greenhouse gases An unchecked rise in greenhouse gases is leading to global climate change.is leading to global climate change.

COCO22 Concentration Concentration Global temperatures Global temperatures

have tracked COhave tracked CO22 concentration for the concentration for the last 500,000 years.last 500,000 years.

Antarctic air bubbles Antarctic air bubbles indicate the current indicate the current COCO22 concentration is concentration is at its highest level in at its highest level in at least 500,000 at least 500,000 years.years.

COCO22 Concentration Concentration

Most of the CO2 increase has happened in last 50 years!

Modeling of Climate ChangeModeling of Climate Change Build climate models Build climate models

based on current/past based on current/past datadata

Models suggest Models suggest recent temperature recent temperature increase is consistent increase is consistent with human with human production of production of greenhouse gases.greenhouse gases.

What makes a planet What makes a planet habitablehabitable??

Located at an optimal distance from the Located at an optimal distance from the Sun for liquid water to existSun for liquid water to exist

What makes a planet What makes a planet habitablehabitable??

Large enough for geological activity to Large enough for geological activity to release and retain water and release and retain water and

atmosphereatmosphere

Planetary DestinyPlanetary Destiny

Earth is Earth is habitable habitable because it is because it is large enough to large enough to remain remain geologically geologically active, and it is active, and it is at the right at the right distance from distance from the Sun so the Sun so oceans could oceans could form.form.

Planetary DestinyPlanetary Destiny

Earth is habitable because it is large enough to remain geologically active, and it is at the right distance from the Sun so oceans could form.

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Chapter 7 Earth and the Terrestrial Worlds

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