EARTH AS A PLANET Chapter 7
Dec 25, 2015
EARTH AS A PLANETEARTH AS A PLANET
Chapter 7
SOME PROPERTIES of SOME PROPERTIES of EARTHEARTH
SOME PROPERTIES of SOME PROPERTIES of EARTHEARTH
Semi major Axis 1.00 AU
Period 1.00 year
Mass 5.98 x 1024 kg
Diameter 12,756 km
Escape Velocity 112. Km/s
Rotation Period 23h 56m 4s
Surface Area 5.1 x 108 km2
Atmospheric Pressure 1.00 bar
EARTH as a PLANETEARTH as a PLANETEARTH as a PLANETEARTH as a PLANET
Only planet with water in liquid Only planet with water in liquid form.form.
Composition: iron, silicates, Composition: iron, silicates, oxygen.oxygen.
Density: highest in Solar System.Density: highest in Solar System.
Interior: 4 major layers - Interior: 4 major layers - core, outer core, mantle, core, outer core, mantle, crust.crust.
EARTH as a PLANETEARTH as a PLANETEARTH as a PLANETEARTH as a PLANET
Only planet with water in liquid Only planet with water in liquid form.form.
Composition: iron, silicates, Composition: iron, silicates, oxygen.oxygen.
Density: highest in Solar System.Density: highest in Solar System. Interior: 4 major layers - core, Interior: 4 major layers - core, outer core, mantle, crust.outer core, mantle, crust.
Magnetic Field and Magnetic Field and Magnetosphere: Earth behaves as Magnetosphere: Earth behaves as if it had a bar magnet inside if it had a bar magnet inside it. it.
MAGNETOSPHERE and VAN MAGNETOSPHERE and VAN ALLEN BELTSALLEN BELTS
MAGNETOSPHERE and VAN MAGNETOSPHERE and VAN ALLEN BELTSALLEN BELTS
The MAGNETOSPHERE The MAGNETOSPHERE SHAPESHAPE
The MAGNETOSPHERE The MAGNETOSPHERE SHAPESHAPE
EARTH’S STRUCTURE – HOW EARTH’S STRUCTURE – HOW DO WE KNOW IT? FROM DO WE KNOW IT? FROM
EARTHQUAKES EARTHQUAKES
EARTH’S STRUCTURE – HOW EARTH’S STRUCTURE – HOW DO WE KNOW IT? FROM DO WE KNOW IT? FROM
EARTHQUAKES EARTHQUAKES
PLATE TECTONICSPLATE TECTONICSPLATE TECTONICSPLATE TECTONICS
Earth’s crust consists of about Earth’s crust consists of about 12 plates. 12 plates.
PLATE TECTONICSPLATE TECTONICSPLATE TECTONICSPLATE TECTONICS
Energy escaping from the Energy escaping from the interior drives the plates (few interior drives the plates (few cm/year).cm/year).
50 million years 50 million years from nowfrom now
PLATE TECTONICSPLATE TECTONICSPLATE TECTONICSPLATE TECTONICS
Where plates interact, dramatic Where plates interact, dramatic changes occur in Earth’s crust.changes occur in Earth’s crust. Rift Zones: Plates pulling apart. Material Rift Zones: Plates pulling apart. Material
rises from mantle to fill spaces (volcanoes). rises from mantle to fill spaces (volcanoes). E.g.. Mid Atlantic Ridge.E.g.. Mid Atlantic Ridge.
PLATE TECTONICSPLATE TECTONICSPLATE TECTONICSPLATE TECTONICS
Where plates interact, dramatic Where plates interact, dramatic changes occur in Earth’s crust.changes occur in Earth’s crust. Subduction Zone: Two plates come together, Subduction Zone: Two plates come together,
once forced down and melts. Earthquakes and once forced down and melts. Earthquakes and volcanoes common along subduction zones.volcanoes common along subduction zones.
PLATE TECTONICSPLATE TECTONICSPLATE TECTONICSPLATE TECTONICS
Coastal BC is on the upper part Coastal BC is on the upper part of a subduction zone. of a subduction zone.
SAN ANDREAS FAULTSAN ANDREAS FAULTSAN ANDREAS FAULTSAN ANDREAS FAULT
ACTIVE SITES on EARTH’S ACTIVE SITES on EARTH’S SURFACESURFACE
ACTIVE SITES on EARTH’S ACTIVE SITES on EARTH’S SURFACESURFACE
ACTIVE SITES on EARTH’S ACTIVE SITES on EARTH’S SURFACESURFACE
ACTIVE SITES on EARTH’S ACTIVE SITES on EARTH’S SURFACESURFACE
CONTINENTAL DRIFTCONTINENTAL DRIFTCONTINENTAL DRIFTCONTINENTAL DRIFT
FLASHCARDFLASHCARDFLASHCARDFLASHCARD
AT 2 CM/YEAR, HOW LONG WOULD IT TAKE A AT 2 CM/YEAR, HOW LONG WOULD IT TAKE A TYPICAL PLATE TO TRAVERSE THE PRESENT TYPICAL PLATE TO TRAVERSE THE PRESENT WIDTH OF THE ATLANTIC OCEAN, ABOUT 6000 WIDTH OF THE ATLANTIC OCEAN, ABOUT 6000 KM? KM?
A)A) 3 X 103 X 1066 YR YR
B)B) 1.2 X 10 1.2 X 1077 YR YR
C)C) 3 X 10 3 X 1088 YR YR
D)D) 1.2 X 10 1.2 X 1099 YR YR
< 10 km, most atmosphere here. (N2 78%, O2 21%, Ar 1%, traces H2O, CO2)
TroposphereTroposphere
10 - 80 km, cold (-50ºC), cloudless StratosphereStratosphere
50 - 80 km, O3, absorbs UV radiation
OzoneOzoneLayerLayer
Atmosphere very thin, constant leakage of H and He
> 100 km> 100 km
GREENHOUSE EFFECTGREENHOUSE EFFECTGREENHOUSE EFFECTGREENHOUSE EFFECT COCO22 content of atmosphere is content of atmosphere is
critical for its role in critical for its role in retaining heat from Sun. retaining heat from Sun. Greenhouse Greenhouse EffectEffect: : Earth absorbs sunlight Earth absorbs sunlight and re-emits it as and re-emits it as infrared (IR) radiation infrared (IR) radiation (Earth acts like a (Earth acts like a
blackbody).blackbody). COCO22 transparent to transparent to
sunlight but absorbs IR sunlight but absorbs IR acting like a blanket. acting like a blanket.
The more COThe more CO22, the , the
hotter Earth is.hotter Earth is.
GREENHOUSE EFFECT and GREENHOUSE EFFECT and GLOBAL WARMINGGLOBAL WARMING
GREENHOUSE EFFECT and GREENHOUSE EFFECT and GLOBAL WARMINGGLOBAL WARMING
Greenhouse effect has raised Greenhouse effect has raised Earth’s average temperature by Earth’s average temperature by 23ºC. 23ºC. Without the greenhouse effect, Without the greenhouse effect, Earth’s average temperature Earth’s average temperature would be below freezing and would be below freezing and Earth would be in a constant Earth would be in a constant global ice age. global ice age.
GREENHOUSE EFFECT and GREENHOUSE EFFECT and GLOBAL WARMINGGLOBAL WARMING
GREENHOUSE EFFECT and GREENHOUSE EFFECT and GLOBAL WARMINGGLOBAL WARMING
COCO22 levels are increasing. levels are increasing. Prediction: rising COPrediction: rising CO22 levels levels will lead to global warming will lead to global warming with uncertain consequences.with uncertain consequences.
THE MOONTHE MOONTHE MOONTHE MOON 1/4 the size of Earth1/4 the size of Earth
THE MOONTHE MOONTHE MOONTHE MOON Earth’s Moon has no atmosphere.Earth’s Moon has no atmosphere.
THE MOONTHE MOONTHE MOONTHE MOON The Moon is tidally locked to Earth.The Moon is tidally locked to Earth.
Non rotating Non rotating MoonMoon
Rotating MoonRotating Moon
THE MOONTHE MOONTHE MOONTHE MOON Only Only extraterrestrial extraterrestrial object that object that humans have humans have visited.visited.
APOLLO MISSIONSAPOLLO MISSIONSAPOLLO MISSIONSAPOLLO MISSIONS
MOON’S INFLUDENCE on MOON’S INFLUDENCE on EARTHEARTH
MOON’S INFLUDENCE on MOON’S INFLUDENCE on EARTHEARTH
Differential forces on Earth Differential forces on Earth tend to stretch Earth slightly.tend to stretch Earth slightly.
TIDAL BULDGES in an TIDAL BULDGES in an “IDEAL” OCEAN“IDEAL” OCEAN
TIDAL BULDGES in an TIDAL BULDGES in an “IDEAL” OCEAN“IDEAL” OCEAN
SPRING and NEAP TIDESSPRING and NEAP TIDESSPRING and NEAP TIDESSPRING and NEAP TIDES
SPRING and NEAP TIDESSPRING and NEAP TIDESSPRING and NEAP TIDESSPRING and NEAP TIDES
MOON’S INFLUDENCE on MOON’S INFLUDENCE on EARTHEARTH
MOON’S INFLUDENCE on MOON’S INFLUDENCE on EARTHEARTH
Tidal friction slowly is Tidal friction slowly is increasing the length of Earth’s increasing the length of Earth’s day. (6 hours 4.5 billion years day. (6 hours 4.5 billion years ago, 22 hours 620 million years ago, 22 hours 620 million years ago)ago)
LIFE on EARTHLIFE on EARTHLIFE on EARTHLIFE on EARTH Earth is the Earth is the onlyonly planet known planet known to be harbouring life.to be harbouring life.
Life arose early on. Fossils Life arose early on. Fossils date back 3.5 billion years.date back 3.5 billion years.
Origin of life is unsure.Origin of life is unsure.Miller experimentMiller experiment: :
produced amino acids produced amino acids and other pre-biological and other pre-biological molecules from molecules from primitive Earth primitive Earth atmosphere - mainly atmosphere - mainly COCO22 (No O (No O22).).
LIFE on EARTHLIFE on EARTHLIFE on EARTHLIFE on EARTH
Development of plants:Development of plants:
Formation of the ozone (OFormation of the ozone (O33) )
layerlayer
Use up COUse up CO22 and produce O and produce O2 2 - photosynthesis- photosynthesis..
Free OFree O22 in atmosphere 2 billion years ago. in atmosphere 2 billion years ago.
Protects Earth from UV.Protects Earth from UV.This allowed life to leave protective oceans This allowed life to leave protective oceans
and colonize the land. Not possible earlier.and colonize the land. Not possible earlier.
COSMIC INFLUENCES on COSMIC INFLUENCES on EARTH’S EVOLUTIONEARTH’S EVOLUTION
COSMIC INFLUENCES on COSMIC INFLUENCES on EARTH’S EVOLUTIONEARTH’S EVOLUTION
Moon is heavily cratered - Moon is heavily cratered - caused by impacts.caused by impacts.Where are Earth’s Where are Earth’s
craters?craters?Most lost by erosion Most lost by erosion
and geological and geological activity.activity.
COSMIC INFLUENCES on COSMIC INFLUENCES on EARTH’S EVOLUTIONEARTH’S EVOLUTION
COSMIC INFLUENCES on COSMIC INFLUENCES on EARTH’S EVOLUTIONEARTH’S EVOLUTION
More than 150 impact craters More than 150 impact craters are still recognized on Earth’s are still recognized on Earth’s surface. surface.
COSMIC INFLUENCES on COSMIC INFLUENCES on EARTH’S EVOLUTIONEARTH’S EVOLUTION
COSMIC INFLUENCES on COSMIC INFLUENCES on EARTH’S EVOLUTIONEARTH’S EVOLUTION Concern is that a large object, Concern is that a large object,
≥10 km, will collide with Earth ≥10 km, will collide with Earth releasing a few billion times releasing a few billion times as much energy as Hiroshima as much energy as Hiroshima bomb. bomb.
COSMIC INFLUENCES on COSMIC INFLUENCES on EARTH’S EVOLUTIONEARTH’S EVOLUTION
COSMIC INFLUENCES on COSMIC INFLUENCES on EARTH’S EVOLUTIONEARTH’S EVOLUTION Concern is that a large object, Concern is that a large object,
10 km, will collide with Earth 10 km, will collide with Earth releasing a few billion times releasing a few billion times as much energy as Hiroshima as much energy as Hiroshima bomb. bomb. One such object crosses Earth’s One such object crosses Earth’s orbit every 100 million years.orbit every 100 million years.
ORBITS of the 100 LARGEST ORBITS of the 100 LARGEST KNOWN NEAR-EARTH KNOWN NEAR-EARTH
ASTEROIDSASTEROIDS
ORBITS of the 100 LARGEST ORBITS of the 100 LARGEST KNOWN NEAR-EARTH KNOWN NEAR-EARTH
ASTEROIDSASTEROIDS
IMPACT FREQUENCYIMPACT FREQUENCYIMPACT FREQUENCYIMPACT FREQUENCY
1.00E-12
1.00E-09
1.00E-06
1.00E-03
1.00E+00
1.00E+03
1.00E+06
1.00E+091.00E-08 1.00E-04 1.00E+00 1.00E+04 1.00E+08
Diameter (Metres)
Mean Time to Impact Earth (Years)
Impactors on the surfce of the space shuttleImpactors on the surfce of the space shuttle11m, 30m, 30secsec
Shooting starsShooting stars1 mm, 30 sec1 mm, 30 sec
MeteroitesMeteroites1m, 1yr1m, 1yr
Arizona CraterArizona Crater100 m, 10100 m, 104 4 yryr
Sudbury, OntarioSudbury, Ontario10 km, 1010 km, 1088 yr yr
COSMIC INFLUENCES on COSMIC INFLUENCES on EARTH’S EVOLUTIONEARTH’S EVOLUTION
COSMIC INFLUENCES on COSMIC INFLUENCES on EARTH’S EVOLUTIONEARTH’S EVOLUTION
More than 150 impact craters More than 150 impact craters are still recognized on Earth’s are still recognized on Earth’s surface. surface.
METEOR CRATERMETEOR CRATER0.1 km meteor0.1 km meteor
Crater size = 10 x Crater size = 10 x size of impacting objectsize of impacting object
1.2 km1.2 km
TUNGUSKA EVENTTUNGUSKA EVENTTUNGUSKA EVENTTUNGUSKA EVENT
SiberiaSiberiaJune 30, 1908June 30, 1908
Projectile Projectile exploded before exploded before impacting Earthimpacting Earth
Projectile’s mass Projectile’s mass estimated to be estimated to be
100,000 tons100,000 tons
Caused Caused widespread widespread
damage.damage.
TUNGUSKA EVENTTUNGUSKA EVENTTUNGUSKA EVENTTUNGUSKA EVENT
SHOEMAKER-LEVI COMETSHOEMAKER-LEVI COMETSHOEMAKER-LEVI COMETSHOEMAKER-LEVI COMET
IMPACTIMPACTIMPACTIMPACT
Earth’s Earth’s ViewView
Voyager’sVoyager’sViewView
SHOEMAKER-LEVI IMPACTSHOEMAKER-LEVI IMPACTSHOEMAKER-LEVI IMPACTSHOEMAKER-LEVI IMPACT
DEVELOPMENT of DUST CLOUDDEVELOPMENT of DUST CLOUDDEVELOPMENT of DUST CLOUDDEVELOPMENT of DUST CLOUD
ImpactImpact
IMPACT DUST CLOUDSIMPACT DUST CLOUDSIMPACT DUST CLOUDSIMPACT DUST CLOUDS
IR IMAGE of IMPACTSIR IMAGE of IMPACTSIR IMAGE of IMPACTSIR IMAGE of IMPACTS
IoIo
COSMIC INFLUENCES on COSMIC INFLUENCES on EARTH’S EVOLUTION con’tEARTH’S EVOLUTION con’tCOSMIC INFLUENCES on COSMIC INFLUENCES on
EARTH’S EVOLUTION con’tEARTH’S EVOLUTION con’t
EFFECTS of a MASSIVE EFFECTS of a MASSIVE IMPACTIMPACT
EFFECTS of a MASSIVE EFFECTS of a MASSIVE IMPACTIMPACT
EFFECTS of a MASSIVE EFFECTS of a MASSIVE IMPACTIMPACT
EFFECTS of a MASSIVE EFFECTS of a MASSIVE IMPACTIMPACT
Huge tidal waves.Huge tidal waves. Dust high up in the atmosphere.Dust high up in the atmosphere. Block out Sun for about one year, kills Block out Sun for about one year, kills
photosynthesis.photosynthesis. World-wide fires, forests and grasslands World-wide fires, forests and grasslands
destroyed.destroyed. Highly acidic rains.Highly acidic rains. Animals depending on plants die Animals depending on plants die
(dinosaurs?), rise of mammals. (dinosaurs?), rise of mammals.
Global earthquakes.Global earthquakes.
EXTINCTIONS, the SOLAR EXTINCTIONS, the SOLAR SYSTEM and our GALAXYSYSTEM and our GALAXYEXTINCTIONS, the SOLAR EXTINCTIONS, the SOLAR SYSTEM and our GALAXYSYSTEM and our GALAXY
Past 100 million years many large scale Past 100 million years many large scale extinctions (~ 10) identified on Earth.extinctions (~ 10) identified on Earth.In these, a significant fraction of existing
species were extinguished. Best known is Best known is extinction of the extinction of the dinosaurs 65 dinosaurs 65 million years ago million years ago after flourishing after flourishing for 100 million for 100 million years.years.
EXTINCTIONS, the SOLAR EXTINCTIONS, the SOLAR SYSTEM and our GALAXYSYSTEM and our GALAXYEXTINCTIONS, the SOLAR EXTINCTIONS, the SOLAR SYSTEM and our GALAXYSYSTEM and our GALAXY
Impact of ~ 20 km asteroid.
Evidence: crater in Gulf of Mexico and Iridium layer.
What caused the extinctions?What caused the extinctions?
EXTINCTIONS, the SOLAR EXTINCTIONS, the SOLAR SYSTEM and our GALAXYSYSTEM and our GALAXYEXTINCTIONS, the SOLAR EXTINCTIONS, the SOLAR SYSTEM and our GALAXYSYSTEM and our GALAXY
What caused the extinctions?What caused the extinctions?
Impact of ~ 20 km asteroid.
Evidence: crater in Gulf of Mexico and Iridium layer.
Nearby supernova (depletes O3, forming NO2).
Crab NebulaCrab Nebula
EXTINCTION of the EXTINCTION of the DINOSAURSDINOSAURS
EXTINCTION of the EXTINCTION of the DINOSAURSDINOSAURS
ALTERNATE DINOSAUR ALTERNATE DINOSAUR EXTINCTION THEORYEXTINCTION THEORY
ALTERNATE DINOSAUR ALTERNATE DINOSAUR EXTINCTION THEORYEXTINCTION THEORY
EXTINCTIONS, the SOLAR EXTINCTIONS, the SOLAR SYSTEM and our GALAXYSYSTEM and our GALAXYEXTINCTIONS, the SOLAR EXTINCTIONS, the SOLAR SYSTEM and our GALAXYSYSTEM and our GALAXY
Supernovae and impacts more likely Supernovae and impacts more likely when Sun passes through spiral arm in when Sun passes through spiral arm in our Galaxyour GalaxyOort cloud comets get perturbed.
SPIRAL GALAXYSPIRAL GALAXYSPIRAL GALAXYSPIRAL GALAXY
OORT CLOUD GETS OORT CLOUD GETS PERTURBEDPERTURBED
OORT CLOUD GETS OORT CLOUD GETS PERTURBEDPERTURBED