CHAPTER 1 CHAPTER 1 Introduction to Planet Introduction to Planet

“Earth” “Earth”

OverviewOverview 70.8% Earth covered by ocean70.8% Earth covered by ocean Interconnected global or world oceanInterconnected global or world ocean Oceans contain 97.2% of surface waterOceans contain 97.2% of surface water

Fig. 1.3ab

Principal oceansPrincipal oceans PacificPacific

Largest, deepestLargest, deepest AtlanticAtlantic

Second largestSecond largest IndianIndian

Mainly in Southern Mainly in Southern HemisphereHemisphere

Principal oceansPrincipal oceans ArcticArctic

Smallest, shallowest, ice-Smallest, shallowest, ice-coveredcovered

Antarctic or Southern OceanAntarctic or Southern Ocean Connects Pacific, Atlantic, and Connects Pacific, Atlantic, and

IndianIndian South of about 50South of about 50oo S latitude S latitude

The Seven SeasThe Seven Seas

Smaller and shallower than oceansSmaller and shallower than oceans Salt waterSalt water Usually enclosed by landUsually enclosed by land

Sargasso Sea defined by surrounding Sargasso Sea defined by surrounding ocean currentsocean currents

N and S Pacific, N and S Atlantic, N and S Pacific, N and S Atlantic, Indian, Arctic, AntarcticIndian, Arctic, Antarctic

Comparison of elevation and Comparison of elevation and depthdepth Average depth 3729 m (12,234 ft)Average depth 3729 m (12,234 ft)

Average elevation 840 m (2756 ft)Average elevation 840 m (2756 ft)

Deepest ocean Mariana Trench Deepest ocean Mariana Trench 11,022 m (36,161 ft)11,022 m (36,161 ft)

Highest Highest continentalcontinental mountain Mt. mountain Mt. Everest 8850 m (29,935 ft)Everest 8850 m (29,935 ft)

Fig. 1.3cd

Early explorationEarly exploration

Pacific Pacific Islanders Islanders traveled long traveled long distances distances Small islands Small islands

widely widely scatteredscattered

Fig. 1.5

European culturesEuropean cultures PhoeniciansPhoenicians

Mediterranean Sea, around Africa, Mediterranean Sea, around Africa, British IslesBritish Isles

GreeksGreeks Pytheas reached Iceland 325 B.C.Pytheas reached Iceland 325 B.C. Ptolemy map 150 A.D.Ptolemy map 150 A.D.

Fig. 1.1

The Middle AgesThe Middle Ages

Vikings explored N. Atlantic Vikings explored N. Atlantic OceanOcean Iceland and Greenland 9Iceland and Greenland 9thth and 10 and 10thth

centuries A.D.centuries A.D. Leif Eriksson Vinland 995 A.D.Leif Eriksson Vinland 995 A.D. Greenland, Vinland settlements Greenland, Vinland settlements

abandoned by 1450 A.D.abandoned by 1450 A.D.

Search for new Eastern trade Search for new Eastern trade routes by searoutes by sea Portugal trade routes around AfricaPortugal trade routes around Africa

((Prince Henry the NavigatorPrince Henry the Navigator)) Europeans explore North and South Europeans explore North and South

AmericaAmericaColumbus, CabotColumbus, Cabot

MagellanMagellan and and del Cañodel Caño circumnavigate worldcircumnavigate world

The Age of Discovery in Europe The Age of Discovery in Europe 1492-15221492-1522

Voyages of Columbus and Voyages of Columbus and MagellanMagellan

Fig. 1.7

British Naval PowerBritish Naval Power

British Isles dominant naval British Isles dominant naval power from 1588 to early 1900spower from 1588 to early 1900s Spanish Armada 1588Spanish Armada 1588

Beginning of voyaging for Beginning of voyaging for sciencescience Capt. James CookCapt. James Cook (1728-1779) (1728-1779)

Ships HMSShips HMS Endeavour, Resolution, Endeavour, Resolution, AdventureAdventure

Mapped many islands in PacificMapped many islands in Pacific Systematically measured ocean Systematically measured ocean

characteristicscharacteristics Marine chronograph (longitude)Marine chronograph (longitude)

Cook’s voyagesCook’s voyages

Fig. 1.8

Nature of scientific inquiryNature of scientific inquiry Natural phenomena governed by Natural phenomena governed by

physical processesphysical processes Physical processes similar today Physical processes similar today

as in the pastas in the past Scientists discover these Scientists discover these

processes andprocesses and Make predictionsMake predictions

Scientific methodScientific method ObservationsObservations HypothesesHypotheses Testing and modification of Testing and modification of

hypotheseshypotheses TheoryTheory Probably true versus absolutely Probably true versus absolutely

truetrue Science is continually developing Science is continually developing

because of new observationsbecause of new observations

Scientific methodScientific method

Fig. 1.9

Formation of Solar System and Formation of Solar System and EarthEarth

Nebular hypothesisNebular hypothesis Nebula=cloud of gases and space Nebula=cloud of gases and space

dustdustMainly hydrogen and heliumMainly hydrogen and helium

Gravity concentrates material at Gravity concentrates material at center of cloud (Sun)center of cloud (Sun)

Protoplanets from smaller Protoplanets from smaller concentrations of matter (eddies)concentrations of matter (eddies)

ProtoearthProtoearth Larger than Earth todayLarger than Earth today Homogeneous compositionHomogeneous composition Bombarded by meteoritesBombarded by meteorites

Moon formed from collision Moon formed from collision with large asteroidwith large asteroid

Heat from solar radiationHeat from solar radiation Initial atmosphere boiled awayInitial atmosphere boiled away Ionized particles (solar wind) Ionized particles (solar wind)

swept away nebular gasesswept away nebular gases

ProtoearthProtoearth

Radioactive heatRadioactive heat Spontaneous disintegration of Spontaneous disintegration of

atomsatoms Heat from contraction (protoplanet Heat from contraction (protoplanet

shrinks due to gravity)shrinks due to gravity) Protoearth partially meltsProtoearth partially melts Density stratification (layered Density stratification (layered

Earth)Earth)

Earth’s internal structureEarth’s internal structure Highest density material at Highest density material at

center (core)center (core) Lowest density material at Lowest density material at

surface (crust)surface (crust) Earth layeredEarth layered

Chemical compositionChemical composition Physical propertiesPhysical properties

Chemical compositionChemical composition CrustCrust

Low-density, mainly silicate Low-density, mainly silicate mineralsminerals

MantleMantle Mainly Fe and Mg silicate Mainly Fe and Mg silicate

mineralsminerals CoreCore

High-density, mainly Fe and NiHigh-density, mainly Fe and Ni

Layered Layered EarthEarth

Fig. 1.14

Physical propertiesPhysical properties

LithosphereLithosphere AsthenosphereAsthenosphere MesosphereMesosphere Outer coreOuter core Inner coreInner core

Physical propertiesPhysical properties LithosphereLithosphere

Cool, rigid, brittleCool, rigid, brittle Surface to about 100 km (62 miles)Surface to about 100 km (62 miles)

AsthenosphereAsthenosphere Warm, plastic, able to flowWarm, plastic, able to flow From 100 km to 700 km (430 miles)From 100 km to 700 km (430 miles)

Fig. 1.15

LithosphereLithosphere

Oceanic crustOceanic crust Underlies ocean basinsUnderlies ocean basins Igneous rock basaltIgneous rock basalt Average thickness 8 km (5 miles)Average thickness 8 km (5 miles) Relatively high densityRelatively high density

3.0 g/cm3.0 g/cm33

Lithosphere- Lithosphere- Crust and Crust and Uppermost mantle fused Uppermost mantle fused togethertogether.. Continental crustContinental crust

Underlies continentsUnderlies continents Igneous rock graniteIgneous rock granite Average thickness 35 km (22 Average thickness 35 km (22

miles)miles) Lower densityLower density

2.7 g/cm2.7 g/cm33

AsthenosphereAsthenosphere

Upper mantleUpper mantle Plastic—deforms by flowingPlastic—deforms by flowing High viscosity—flows slowlyHigh viscosity—flows slowly

Isostatic adjustmentIsostatic adjustment BuoyancyBuoyancy

Less dense “floats” higher than more denseLess dense “floats” higher than more dense

Continental crust “floats” higher Continental crust “floats” higher than oceanic crust on plastic than oceanic crust on plastic asthenosphereasthenosphere

Fig. 1.16

Origin of Earth’s Origin of Earth’s atmosphereatmosphere Partial melting resulted in Partial melting resulted in

outgassingoutgassing about 4 billion years about 4 billion years agoago Similar to gases emitted from Similar to gases emitted from

volcanoesvolcanoes Mainly water vaporMainly water vapor Carbon dioxide, hydrogenCarbon dioxide, hydrogen Other gases such as methane and Other gases such as methane and

ammoniaammonia

Origin of Earth’s oceansOrigin of Earth’s oceans

Water vapor released by Water vapor released by outgassingoutgassing

Condensed as rainCondensed as rain Accumulated in ocean basinsAccumulated in ocean basins About 4 billion years agoAbout 4 billion years ago Ice Comets were also important Ice Comets were also important

to adding water to the Earth to adding water to the Earth systemsystem

Fig. 1.17

Ocean salinityOcean salinity Rain dissolves rocksRain dissolves rocks Dissolved compounds (ions) Dissolved compounds (ions)

accumulate in ocean basinsaccumulate in ocean basins Ocean salinity based on Ocean salinity based on

balance between input and balance between input and output of ionsoutput of ions

Ocean salinity nearly constant Ocean salinity nearly constant over past 4 billion yearsover past 4 billion years

Life in oceansLife in oceans

Earliest life forms fossilized Earliest life forms fossilized bacteria in rocks about 3.5 bacteria in rocks about 3.5 billion years oldbillion years old

Marine rocksMarine rocks Life originated in oceans?Life originated in oceans?

Stanley Miller’s experimentStanley Miller’s experiment

Organic molecules formed by Organic molecules formed by ultraviolet light, electrical spark ultraviolet light, electrical spark (lightning), and mixture of water, (lightning), and mixture of water, carbon dioxide, hydrogen, methane, carbon dioxide, hydrogen, methane, and ammoniaand ammonia

Fig. 1.18a

Evolution and natural Evolution and natural selectionselection Organisms adapt and change Organisms adapt and change

through timethrough time Advantageous traits are naturally Advantageous traits are naturally

selectedselected Traits inheritedTraits inherited Organisms adapt to environmentsOrganisms adapt to environments Organisms change environmentsOrganisms change environments

Types of life formsTypes of life forms HeterotrophsHeterotrophs (most bacteria (most bacteria

and animals)and animals) AutotrophsAutotrophs (algae and (algae and

plants)plants) Anaerobic bacteria Anaerobic bacteria

(chemosynthesis)(chemosynthesis) Photosynthetic autotrophsPhotosynthetic autotrophs

Chlorophyll captures solar Chlorophyll captures solar energyenergy

Photosynthesis and Photosynthesis and respirationrespiration

Fig. 1.19

Oxygen crisisOxygen crisis Photosynthetic bacteria release Photosynthetic bacteria release

oxygen (Ooxygen (O22) to atmosphere) to atmosphere About 2 billion years ago, About 2 billion years ago,

sufficient Osufficient O22 in atmosphere to in atmosphere to oxidize (rust) rocksoxidize (rust) rocks

Ozone (OOzone (O33) builds up in ) builds up in atmosphereatmosphere Protects Earth’s surface from Protects Earth’s surface from

ultraviolet solar radiationultraviolet solar radiation

Oxygen crisisOxygen crisis

About 1.8 billion years ago, most About 1.8 billion years ago, most anaerobic bacteria killed off by anaerobic bacteria killed off by OO22-rich atmosphere-rich atmosphere

Photosynthetic organisms Photosynthetic organisms created today’s Ocreated today’s O22-rich -rich atmosphere atmosphere OO22 makes up about 21% of gases in makes up about 21% of gases in

modern atmospheremodern atmosphere Animals thriveAnimals thrive

Age of EarthAge of Earth Radiometric age datingRadiometric age dating

Spontaneous change/decaySpontaneous change/decay Half-lifeHalf-life

Earth is about 4.6 billion years oldEarth is about 4.6 billion years old

Fig. 1.22

Geologic Geologic time scaletime scale

Fig. 1.H

End of End of CHAPTER 1 CHAPTER 1 Introduction Introduction to Planet to Planet “Earth”“Earth”