Earth’s EvolutionThrough Geologic

Time

Why is Earth Unique?Why is Earth Unique?

• Life is ubiquitousLife is ubiquitous! – It’s everywhere!! – It’s everywhere!

• Just the right size Just the right size – gravitational forces hold a relatively thin atmosphere– gravitational forces hold a relatively thin atmosphere

• Earth possesses a metallic core Earth possesses a metallic core – supports a magnetic field protecting life– supports a magnetic field protecting life from lethal cosmic raysfrom lethal cosmic rays

• Just the right distance from the sun Just the right distance from the sun – 93 million miles allowing water– 93 million miles allowing water to exist in all three phases (solid, liquid, gas)to exist in all three phases (solid, liquid, gas)

• Just the right time Just the right time – enough time for microorganisms to photosynthesize – enough time for microorganisms to photosynthesize anan oxygen-rich atmosphere 2.2 billion years agooxygen-rich atmosphere 2.2 billion years ago

• Just the right time Just the right time – asteroid impact about 65 million years ago creates – asteroid impact about 65 million years ago creates mass extinction allowing the proliferation of mammalsmass extinction allowing the proliferation of mammals

• Plate Tectonic Processes Plate Tectonic Processes – recycling lithospheric material– recycling lithospheric material• External forces vs. Internal forcesExternal forces vs. Internal forces

So, how did earth become what it is today?

4600 my

542 my

251 my

65 my

88% ofGeologic Time

291 my

186 my

I I I I The Geologic Time Scale. The Geologic Time Scale. The Geologic Time Scale. The Geologic Time Scale. 1.1.Write down the Geologic Time Scale.Write down the Geologic Time Scale. Include in your time scale the following:Include in your time scale the following:

EonsEons ErasEras periodsperiods

Epochs for the Epochs for the CenozoicCenozoic and and TertiaryTertiary periods periods

2. Write a “mnemonic” phrase for the periods2. Write a “mnemonic” phrase for the periods

10

Start of the Precambrian 4.6 by

• explosion from a single pointexplosion from a single point• universe expandinguniverse expanding• explosion from a single pointexplosion from a single point• universe expandinguniverse expanding

• fusion beginsfusion begins• fusion beginsfusion begins• cooling H, Hecooling H, He• cooling H, Hecooling H, He• contribution of heavycontribution of heavy elements elements • contribution of heavycontribution of heavy elements elements

• contraction prtosun• contraction prtosun• more contraction / accretionmore contraction / accretion• more contraction / accretionmore contraction / accretion

planetesimalsplanetesimalsplanetesimalsplanetesimals

EarthEarth

chemical chemical differentiationdifferentiation

chemical chemical differentiationdifferentiation

Primitive atmospherestarts to form during the

Hadean Eon

The Hadean Eon (4.6 b.y.): “hellish” conditions

In Earth’s early formation:In Earth’s early formation:• atmosphere: H, He, CHatmosphere: H, He, CH44, NH, NH33, CO, CO22, H, H22OOvaporvapor

• weak gravity H, He is lost to spaceweak gravity H, He is lost to space

• T-TauriT-Tauri phase (high solar winds) removed all the other gasses phase (high solar winds) removed all the other gasses

In Earth’s early formation:In Earth’s early formation:• atmosphere: H, He, CHatmosphere: H, He, CH44, NH, NH33, CO, CO22, H, H22OOvaporvapor

• weak gravity H, He is lost to spaceweak gravity H, He is lost to space

• T-TauriT-Tauri phase (high solar winds) removed all the other gasses phase (high solar winds) removed all the other gasses

As the Earth begins to cool…As the Earth begins to cool…As the Earth begins to cool…As the Earth begins to cool…

Earth’s First Enduring Atmosphere:Earth’s First Enduring Atmosphere:• produced by outgassing – gasses escape from the Earth’s interiorproduced by outgassing – gasses escape from the Earth’s interior

• outgassing produced by hundreds of active volcanoesoutgassing produced by hundreds of active volcanoes• Earth was in a “fluid state,” releasing high amts of gasEarth was in a “fluid state,” releasing high amts of gas

• Earth’s atmosphere from outgassingEarth’s atmosphere from outgassing• water vapor, COwater vapor, CO22, SO, SO22, minor amounts of other gasses, minor amounts of other gasses

Earth’s First Enduring Atmosphere:Earth’s First Enduring Atmosphere:• produced by outgassing – gasses escape from the Earth’s interiorproduced by outgassing – gasses escape from the Earth’s interior

• outgassing produced by hundreds of active volcanoesoutgassing produced by hundreds of active volcanoes• Earth was in a “fluid state,” releasing high amts of gasEarth was in a “fluid state,” releasing high amts of gas

• Earth’s atmosphere from outgassingEarth’s atmosphere from outgassing• water vapor, COwater vapor, CO22, SO, SO22, minor amounts of other gasses, minor amounts of other gasses

So, where is the oxygen?So, where is the oxygen?So, where is the oxygen?So, where is the oxygen?

Oxygen in the Earth’s AtmosphereOxygen in the Earth’s AtmosphereOxygen in the Earth’s AtmosphereOxygen in the Earth’s Atmosphere

• A cooling earth A cooling earth Condensing water vapor (clouds) Condensing water vapor (clouds) and rain, producing the oceans (filling in low areas) and rain, producing the oceans (filling in low areas)

• A cooling earth A cooling earth Condensing water vapor (clouds) Condensing water vapor (clouds) and rain, producing the oceans (filling in low areas) and rain, producing the oceans (filling in low areas)

• Photosynthesizing bacteria release oxygen into thePhotosynthesizing bacteria release oxygen into the water---- 3.5 billion years agowater---- 3.5 billion years ago

• COCO22 + H + H22O + Energy O + Energy sunsun --> Oxygen --> Oxygen

• Photosynthesizing bacteria release oxygen into thePhotosynthesizing bacteria release oxygen into the water---- 3.5 billion years agowater---- 3.5 billion years ago

• COCO22 + H + H22O + Energy O + Energy sunsun --> Oxygen --> Oxygen

4.0 b.y.

Cynobacteria(blue-green algae)

• Oxygen reacts with iron, creating banded ironOxygen reacts with iron, creating banded iron formations (3.5 – 2 b.y. ago)formations (3.5 – 2 b.y. ago)

• iron + oxygen --> RUSTiron + oxygen --> RUST• alternating layers of chert and iron-rich alternating layers of chert and iron-rich rocksrocks

• Oxygen reacts with iron, creating banded ironOxygen reacts with iron, creating banded iron formations (3.5 – 2 b.y. ago)formations (3.5 – 2 b.y. ago)

• iron + oxygen --> RUSTiron + oxygen --> RUST• alternating layers of chert and iron-rich alternating layers of chert and iron-rich rocksrocks

Banded Iron Formations

• Increasing oxygen-generating organismsIncreasing oxygen-generating organisms• oxygen increased steadily to stable concentrationsoxygen increased steadily to stable concentrations• “ “the oxygen explosion” forms ozone (Othe oxygen explosion” forms ozone (O33))

• formed in the stratosphereformed in the stratosphere• protects life (DNA) from UV radiationprotects life (DNA) from UV radiation

• Increasing oxygen-generating organismsIncreasing oxygen-generating organisms• oxygen increased steadily to stable concentrationsoxygen increased steadily to stable concentrations• “ “the oxygen explosion” forms ozone (Othe oxygen explosion” forms ozone (O33))

• formed in the stratosphereformed in the stratosphere• protects life (DNA) from UV radiationprotects life (DNA) from UV radiation

Stable O2 levelsby 1.5 b.y.

Banded Iron FormationsBanded Iron Formations

•Deposited during the Precambrian EonDeposited during the Precambrian Eon• 3.5 to 2 billion years ago3.5 to 2 billion years ago

Banded Iron FormationsBanded Iron Formations

•Deposited during the Precambrian EonDeposited during the Precambrian Eon• 3.5 to 2 billion years ago3.5 to 2 billion years ago

Evolution of the Earth’s OceansEvolution of the Earth’s OceansEvolution of the Earth’s OceansEvolution of the Earth’s Oceans

About 90% of the current volume of seawaterAbout 90% of the current volume of seawaterwas contained in the ocean basins (4.0 b.y.)was contained in the ocean basins (4.0 b.y.)About 90% of the current volume of seawaterAbout 90% of the current volume of seawaterwas contained in the ocean basins (4.0 b.y.)was contained in the ocean basins (4.0 b.y.)

Earth’s atmosphere rich in HEarth’s atmosphere rich in H22S , COS , CO22, SO, SO22

• Rain + HRain + H22S, COS, CO2,2, and SO and SO22 ACID RAIN ACID RAIN• Highly acidic rain Highly acidic rain accelerated weathering accelerated weathering• Na, K, Ca, Si ions carried into the oceanNa, K, Ca, Si ions carried into the ocean

• Some dissolved ions ppt Some dissolved ions ppt chemical sediment chemical sediment• Other ions increased ocean salinity Other ions increased ocean salinity

Earth’s atmosphere rich in HEarth’s atmosphere rich in H22S , COS , CO22, SO, SO22

• Rain + HRain + H22S, COS, CO2,2, and SO and SO22 ACID RAIN ACID RAIN• Highly acidic rain Highly acidic rain accelerated weathering accelerated weathering• Na, K, Ca, Si ions carried into the oceanNa, K, Ca, Si ions carried into the ocean

• Some dissolved ions ppt Some dissolved ions ppt chemical sediment chemical sediment• Other ions increased ocean salinity Other ions increased ocean salinity

COCO22 (major greenhouse gas) readily soluble (major greenhouse gas) readily soluble

in seawater (the oceans) in seawater (the oceans)

COCO22 (major greenhouse gas) readily soluble (major greenhouse gas) readily soluble

in seawater (the oceans) in seawater (the oceans)

CO2 + H2O + Ca+2 CaCO3 (Limestone)(Limestone)CO2 + H2O + Ca+2 CaCO3 (Limestone)(Limestone)

AtmosphericAtmosphericCOCO22

AtmosphericAtmosphericCOCO22

Dissolved ionsDissolved ionsin the oceanin the ocean

Dissolved ionsDissolved ionsin the oceanin the ocean

Organisms extract Organisms extract CaCOCaCO33 shells and die shells and die

producing LS-sedimentproducing LS-sediment

Organisms extract Organisms extract CaCOCaCO33 shells and die shells and die

producing LS-sedimentproducing LS-sediment

White Cliffs of Dover, England

Thick chalk sequence (CaCO3) deposited during the Precambrian

Eon – 542 million years ago

• Formation of the Earth’sFormation of the Earth’s metallic core (Fe, Ni) and metallic core (Fe, Ni) and rocky mantle rocky mantle

• Formation of the Earth’sFormation of the Earth’s metallic core (Fe, Ni) and metallic core (Fe, Ni) and rocky mantle rocky mantle

• Low density, low silica mineralsLow density, low silica minerals move from the mantle towardmove from the mantle toward surface – lighter material risessurface – lighter material rises

• Low density, low silica mineralsLow density, low silica minerals move from the mantle towardmove from the mantle toward surface – lighter material risessurface – lighter material rises

• Formation of the lithosphere (thin crust)Formation of the lithosphere (thin crust)• continental crustcontinental crust• oceanic crustoceanic crust

• Formation of the lithosphere (thin crust)Formation of the lithosphere (thin crust)• continental crustcontinental crust• oceanic crustoceanic crust

Lithosphere

2.7 g/cm2.7 g/cm33

3.0 g/cm3.0 g/cm333.0 g/cm3.0 g/cm33

5.5 g/cm5.5 g/cm335.5 g/cm5.5 g/cm33

• Partial melting of mantle basaltic rocks (ocean crust) D = 3.0 g/cm3

• Partial melting of basaltic rocks lower density continental crust D= 2.7 g/cm3

Continued Chemical Differentiation

Acasta gneissNW Canada

4.0 b.y.

Making Earth’s Continents

OldestRocks

Making Earth’s ContinentsMaking Earth’s ContinentsMaking Earth’s ContinentsMaking Earth’s Continents

The crust is on the move through plate tectonic activity. SubductionThe crust is on the move through plate tectonic activity. Subductionof lithospheric material of lithospheric material numerous isolated island arc systems. numerous isolated island arc systems.The crust is on the move through plate tectonic activity. SubductionThe crust is on the move through plate tectonic activity. Subductionof lithospheric material of lithospheric material numerous isolated island arc systems. numerous isolated island arc systems.

Collision (convergence) and accretion of various island arc systemsCollision (convergence) and accretion of various island arc systems• deformed and metamorphosed sedimentdeformed and metamorphosed sediment• shortening and thickening of continental crustshortening and thickening of continental crust• silica-rich magmas (less dense) ascend and intrude rocks abovesilica-rich magmas (less dense) ascend and intrude rocks above• continued accretion continued accretion cratonscratons

• modern-day exposed cratons are known as modern-day exposed cratons are known as stable shieldsstable shields

Collision (convergence) and accretion of various island arc systemsCollision (convergence) and accretion of various island arc systems• deformed and metamorphosed sedimentdeformed and metamorphosed sediment• shortening and thickening of continental crustshortening and thickening of continental crust• silica-rich magmas (less dense) ascend and intrude rocks abovesilica-rich magmas (less dense) ascend and intrude rocks above• continued accretion continued accretion cratonscratons

• modern-day exposed cratons are known as modern-day exposed cratons are known as stable shieldsstable shields

The Making of North America

oldest

youngest

oldest

youngest

Piecemeal assembly into a continent

• Continued plate tectonic activity accretion of island arc systems known as crustal provinces

• About 1.9 billion years crustal provinces converged Trans-Hudson Mt. belt

• Other crustal provinces added over geologic time

“Accretion of Crustal Provinces”

I I I I the early earth .the early earth .the early earth .the early earth .

3. Describe the atmospheric condition during 3. Describe the atmospheric condition during the Hadean Eon.the Hadean Eon.

4. Describe the significance of the banded iron 4. Describe the significance of the banded iron formations.formations.

5. Explain how abundant concentrations of 5. Explain how abundant concentrations of limestone (CaCOlimestone (CaCO33) were deposited during the ) were deposited during the Precambrian Eon.Precambrian Eon.

6. How would you describe a craton?6. How would you describe a craton?

Supercontinents of the PrecambrianSupercontinent Cycle:

• cyclic rifting and dispersal of one supercontinent followed by a long period of gradual reconstruction a new supercontinent

RODINIA:• Supercontinent dominating the Precambrian Eon

• Breaks apart by the end of the PC

GONDWANABetween 800-600 m.y.fragments of Rodinia becomeGondwana (Southern Hemisphere)

“Future Pangaea”Continents that will form

Pangaea during the Phanerozoic Eon

Geologic History of the Phanerozoic EonThe Formation of Earth’s Modern Continents

Phanerozoic encompassesapproximately 542 million years

of geologic time.

The Phanerozoic Eon:• Marks the appearance of first life forms

• Increased availability of fossils improved age accuracy

• Abundant organisms associated with various niches invaluable information to ancient environments

Paleozoic Era

Mesozoic Era

Cenozoic Era

291 m.y.291 m.y.291 m.y.291 m.y.

186 m.y.186 m.y.186 m.y.186 m.y.

65+ m.y.65+ m.y.65+ m.y.65+ m.y.

Phanerozoic Eon is divided into 3 main eras.

The Phanerozic Eonrepresents about

12% of the geologictime scale

Evolution of the supercontinentPangaea during the Paleozoic

EQLaurasia

Laurasia• warm, wet tropical conditions• abundant swampy conditions• future coal deposits (Mississippian)

Laurasia + Gondwana = Pangaea

Pangaea• The accretion of Pangaea resulted in:

• collision of northern Europe with Greenland Caledonian Mountains-A• joining of northern Asia (Siberia) and Europe Ural Mountains- B

• Joining of North Africa and Eastern U.S. Appalachian Mountains- C During the formation of the Appalachian Mountains, Pangaea was at its maximum size.

A

B

C

Mesozoic History – 186 million years (Triassic, Jurassic, Cretaceous)

Triassic Period• Breakup of Pangaea modern day continents

• Much of the current continents above sea level evidenced by massive terrestrial sandstone, mudstone deposits

Triassic Period• Breakup of Pangaea modern day continents

• Much of the current continents above sea level evidenced by massive terrestrial sandstone, mudstone deposits

Jurassic Period• Regressive / Transgressive seas deposit thick sequences of sedimentary rocks

• Colorado Plateau (Grand Canyon, Bryce Canyon) stratigraphy The Navajo Sandstone – 300m thick (1000 feet)

• Middle Jurassic – enormous desert (American-Southwest) evidenced by ancient sand dune remnants

• Steven Spielberg makes the movie Jurassic Park???

Jurassic Period• Regressive / Transgressive seas deposit thick sequences of sedimentary rocks

• Colorado Plateau (Grand Canyon, Bryce Canyon) stratigraphy The Navajo Sandstone – 300m thick (1000 feet)

• Middle Jurassic – enormous desert (American-Southwest) evidenced by ancient sand dune remnants

• Steven Spielberg makes the movie Jurassic Park???

Cretaceous Period• Continued break-up of Pangaea forming the Atlantic Ocean• Westward-moving North American plate converging with the Pacific basin

• Subduction of the Farallon plate (Pacific plate) producing coast ranges, Sierra Nevada Mts, Idaho batholith• Laramide orogeny Formation of the Rocky Mountains

Cretaceous Period• Continued break-up of Pangaea forming the Atlantic Ocean• Westward-moving North American plate converging with the Pacific basin

• Subduction of the Farallon plate (Pacific plate) producing coast ranges, Sierra Nevada Mts, Idaho batholith• Laramide orogeny Formation of the Rocky Mountains

Massive cross-bedded sandstonesdeposited during Middle Jurassic Period

I I I I The Paleozoic Era.The Paleozoic Era. The Paleozoic Era.The Paleozoic Era. 7. Distinguish between the following tectonic 7. Distinguish between the following tectonic landmasses (when they occurred geologically):landmasses (when they occurred geologically):

Rodinia, Gondwana, Laurasia, PangaeaRodinia, Gondwana, Laurasia, Pangaea

8. How did the Appalachian Mountains form?8. How did the Appalachian Mountains form?

9. Describe at least one significant geologic event9. Describe at least one significant geologic event that has taken place during the Triassic, that has taken place during the Triassic, Jurassic, and Cretaceous periods.Jurassic, and Cretaceous periods.

Continent ConfigurationCenozoic Era

Cenozoic History – 65 million years (Tertiary, Quaternary Periods)

Cenozoic Era – “era of recent life”• Only a small amount of geologic time, but more is known about the Cenozoic than other eras (WHY?)

• rocks units widespread and less disturbed• higher levels of fossil preservation

Eastern North America (N.A.) during the Cenozoic Era• Most of N.A. above sea level

• Eastern N.A. “passive” tectonic boundary

• tectonically stable – considered a tectonic trailing edge

• erosional processes > tectonic processes

• abundant marine deposition (transgression of seas) along the Gulf of Mexico numerous petroleum traps

• early Cenozoic --- Most of the Appalachian Mountains eroded the eastern seaboard

Eastern North America (N.A.) during the Cenozoic Era• Most of N.A. above sea level

• Eastern N.A. “passive” tectonic boundary

• tectonically stable – considered a tectonic trailing edge

• erosional processes > tectonic processes

• abundant marine deposition (transgression of seas) along the Gulf of Mexico numerous petroleum traps

• early Cenozoic --- Most of the Appalachian Mountains eroded the eastern seaboard

United States Geologic Map

Transgression of seasduring the Cenozoic

Erosion of the AppalachiansErosion of the Appalachians

“passive tectonic margin”trailing edge

“passive tectonic margin”trailing edge

Eastern United StatesCenozoic geology

Western United StatesWestern United States

Western N.A. during the Cenozoic Era

• Laramide Orogeny the Rocky Mountains coming to an end.• erosion of the Rocky Mountains sediments deposited (clastic-wedge), making the Great Plains

• Miocene Epoch (20 m.y. ago):

•Nevada into Mexico experienced crustal extension Basin and Province Range

• Faulted blocks (horst and grabens) extending from Nevada into Utah and portions of Mexico

• Rocky Mountains re-uplifted• creating the Grand Canyon, Colorado• creating the Grand Canyon, Snake River, Idaho

• Flood basalts in Oregon-Washington (CRB’s)• Flood basalts range in thickness up to 1 mile

• Continued convergence producing the Cascade Volcanoes• subduction of the Farallon plate stratacomposite volcanoes

• Sierra Nevada batholith, Idaho batholith faulted and uplifted• Mesozoic batholiths exposed to the surface

• The onset of the San Andreas Fault• A portion of California (North American Plate) begins to “slide” northwest against the Pacific plate.

Western United States Cenozoic Geology

United States Geologic Map

Crustal ExtensionCrustal Extension

Flood BasaltsCRB

Flood BasaltsCRB

Cascade VolcanoesCascade Volcanoes

Sierra Nevadabatholith

Sierra Nevadabatholith

Onset of the San Andreas Fault

Onset of the San Andreas Fault

Larmide Orogeny endsErosion of the Rocky Mountains

The Great Plains

Larmide Orogeny endsErosion of the Rocky Mountains

The Great Plains

I I I I the Cenozoic Era.the Cenozoic Era. the Cenozoic Era.the Cenozoic Era. 10. Describe at least 3 geologic events taking place10. Describe at least 3 geologic events taking place in Eastern U.S. and 3 geologic events in Westernin Eastern U.S. and 3 geologic events in Western U.S.U.S.11. Why is the Eastern section of the U.S. less 11. Why is the Eastern section of the U.S. less tectonically active than the Western U.S.?tectonically active than the Western U.S.?

12. What is significant about the Laramide 12. What is significant about the Laramide Orogeny?Orogeny?

The Geologic Time Scaleand the association of lifewill continue in the next

section.