EARTH AS A PLANET Chapter 7 SOME PROPERTIES of EARTH Semi major Axis1.00 AU Period1.00 year Mass5.98 x 10 24 kg Diameter12,756 km Escape Velocity112

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.


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


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.


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.


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




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 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.



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


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



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


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.



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 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 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



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




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.


Impact of ~ 20 km asteroid.

Evidence: crater in Gulf of Mexico and Iridium layer.

What caused the extinctions?What caused the extinctions?


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


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

Documents

EARTH AS A PLANET Chapter 7 SOME PROPERTIES of EARTH Semi major Axis1.00 AU Period1.00 year Mass5.98 x 10 24 kg Diameter12,756 km Escape Velocity112