Evolution of Life and Evolution of Life and EarthEarth

(Historical Geology)(Historical Geology)

Physical vs. Historical Physical vs. Historical GeologyGeology

► Physical Geology-Physical Geology- Origin, classification, Origin, classification, and composition of Earth materials and and composition of Earth materials and internal and surficial processesinternal and surficial processes

► Historical Geology-Historical Geology- Earth evolution, Earth evolution, changes in lands and seas, mountain changes in lands and seas, mountain building and destruction, fossil succession building and destruction, fossil succession through time, and history of the solar through time, and history of the solar systemsystem

Scientific MethodScientific Method

QuestionsQuestions Collection of DataCollection of Data Development of HypothesisDevelopment of Hypothesis Testing of HypothesisTesting of Hypothesis

The beginningThe beginning

►The Big BangThe Big Bang Most scientist believe that the universe Most scientist believe that the universe

was created in a single event known as was created in a single event known as the the Big BangBig Bang►This occurred ~15 billion years agoThis occurred ~15 billion years ago

Some studies suggest 22 byaSome studies suggest 22 bya

Our Solar System started to form about 5 Our Solar System started to form about 5 byabya

Our Solar SystemOur Solar System

► Solar Nebula HypothesisSolar Nebula Hypothesis Cold, Rarified cloud of gas and Cold, Rarified cloud of gas and

dust particlesdust particles Dust cloud starts Dust cloud starts

counterclockwise rotation counterclockwise rotation around proto-sunaround proto-sun

Eddies in dust cloud begin Eddies in dust cloud begin planetary development: cold planetary development: cold homogeneous accretionhomogeneous accretion

Final Phase of FormationFinal Phase of Formation

► Eventually, gravitational collapse at Eventually, gravitational collapse at core of rotating disc forms the Suncore of rotating disc forms the Sun

Solar wind drives out lighter elements Solar wind drives out lighter elements Leaving heavy elements in inner solar Leaving heavy elements in inner solar

system and lighter elements in outer system and lighter elements in outer systemsystem

EarthEarth

► Formative IntervalFormative Interval Hadean Eon: 4.6-3.9 byaHadean Eon: 4.6-3.9 bya

► Accretion and DifferentiationAccretion and Differentiation Heating, partial melting and solid Heating, partial melting and solid

diffusiondiffusion Ni and Fe migration to coreNi and Fe migration to core Mantle separation forming lighter crustMantle separation forming lighter crust

Differentiation Differentiation

►Source of Internal heatSource of Internal heat Accretionary heatAccretionary heat Heat caused during bombardmentHeat caused during bombardment Radioactive decayRadioactive decay

►Development of Magnetic FieldDevelopment of Magnetic Field Caused by movement of liquid coreCaused by movement of liquid core

Crustal DevelomentCrustal Develoment

► Crust formed by cooling magma Crust formed by cooling magma oceanocean► KomatititesKomatitites formed early in Earth’s crust formed early in Earth’s crust► Continental Crust and Water present as early Continental Crust and Water present as early

as 4.4 byaas 4.4 bya

Evolution of the Atmosphere Evolution of the Atmosphere and Hydrosphereand Hydrosphere

► Primitive atmosphere before 3.8byaPrimitive atmosphere before 3.8bya

The OceansThe Oceans

► Origin of Oceans (After 4.4bya)Origin of Oceans (After 4.4bya)

Tied to the onset of the Hydrologic cycleTied to the onset of the Hydrologic cycle Salinity due to chemical weatheringSalinity due to chemical weathering

Standard Geologic Time Standard Geologic Time ScaleScale

► Divisions of TimeDivisions of Time Eons (largest): Hadean, Archean, Eons (largest): Hadean, Archean,

Proterozoic, and PhanerozoicProterozoic, and Phanerozoic Eras- units within eons: Eras within the Eras- units within eons: Eras within the

Phanerozoic are the Paleozoic, the Phanerozoic are the Paleozoic, the Mesozoic, and the Cenozoic.Mesozoic, and the Cenozoic.

Periods, Epochs and Ages: decreasing Periods, Epochs and Ages: decreasing order subdivisions of geologic timeorder subdivisions of geologic time

Understanding Earth’s Understanding Earth’s ChangesChanges

► CatastrophismCatastrophism - - Earth surface changes through Earth surface changes through large scale eventslarge scale events

► UniformitarianismUniformitarianism James HuttonJames Hutton

► Dynamic/Cyclic Concept of Earth HistoryDynamic/Cyclic Concept of Earth History► Used principle of actualism (uniformitarianism)Used principle of actualism (uniformitarianism)► Wrote first great Geology text ( Theory of the Wrote first great Geology text ( Theory of the

Earth)Earth)