op ch13 lecture_earth3, understanding of earth history,

Earth: Portrait of a PlanetEarth: Portrait of a Planet

33rdrd Edition Edition Chapter 13

Norton Media LibraryNorton Media Library

http://www.wwnorton.com/college/geo/earth2/content/chapter_4/overview.htm


A Biography of Earth

A Biography of Earth

Prepared by

Ronald ParkerEarlham College Department of Geosciences

Richmond, Indiana

Prepared by

Ronald ParkerEarlham College Department of Geosciences

Richmond, Indiana

Chapter 13: A Biography of Earth Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak

Earth Has a HistoryEarth Has a History Geologic materials record enormous changes.Geologic materials record enormous changes. Earth is a complex, evolving system.Earth is a complex, evolving system.

Physical and biological systems continuously interact.Physical and biological systems continuously interact. Earth constantly changes and has done so through time.Earth constantly changes and has done so through time.

Species arise, flourish and disappear forever.Species arise, flourish and disappear forever.Continents rift, drift and collide.Continents rift, drift and collide.Ocean basins open and close.Ocean basins open and close.Sea-level rises and falls.Sea-level rises and falls.


Methods for Studying the PastMethods for Studying the Past Historic Earth changes are measured by…Historic Earth changes are measured by…

Orogenic events.Orogenic events. Sea level.Sea level. Climates.Climates. Living organisms.Living organisms. Continental positions.Continental positions. Plate boundaries. Plate boundaries. Chemistry.Chemistry.

Atmosphere.Atmosphere.Ocean.Ocean.

Depositional environments. Depositional environments.

These changes are recorded in rocks.These changes are recorded in rocks.


Methods for Studying the PastMethods for Studying the Past Earth history is not always easy to decipher.Earth history is not always easy to decipher.

Much of the record of past events is incomplete. Why?Much of the record of past events is incomplete. Why?The record didn’t accumulate continuously. The record didn’t accumulate continuously. Erosion destroys the record with age as a variable.Erosion destroys the record with age as a variable.

Younger rocks are better preserved; older rocks less so.Younger rocks are better preserved; older rocks less so.


Methods for Studying the PastMethods for Studying the Past Earth history is not always easy to decipher.Earth history is not always easy to decipher.

Despite erosion, there is still an abundance of evidence.Despite erosion, there is still an abundance of evidence. This evidence is often readily observed by looking at rocks.This evidence is often readily observed by looking at rocks.


Methods for Studying the PastMethods for Studying the Past Ancient orogens – Former mountain belts.Ancient orogens – Former mountain belts.

Igneous activity, deformation and metamorphism.Igneous activity, deformation and metamorphism. Thick sedimentary deposits filling foreland basins.Thick sedimentary deposits filling foreland basins. Ancient orogenic belts expose deeply buried rocks. Ancient orogenic belts expose deeply buried rocks.


Methods for Studying the PastMethods for Studying the Past Clear evidence of continental growth over time.Clear evidence of continental growth over time.

Continents grow by addition along edges.Continents grow by addition along edges.Continental interiors are older.Continental interiors are older.Rocks become youngerRocks become younger

toward margins.toward margins.


Methods for Studying the PastMethods for Studying the Past Recognizing depositional environments.Recognizing depositional environments.

Successions of strata record changes Successions of strata record changes

in depositional settings. in depositional settings.

Recognizing sea-level changes.Recognizing sea-level changes. Sediments record sea-level flux.Sediments record sea-level flux. Shallow and deep environmentsShallow and deep environments

create distinctive sediments. create distinctive sediments.


Methods for Studying the PastMethods for Studying the Past Changing continental positions are preserved.Changing continental positions are preserved.

Paleomagnetism captures paleolatitude. Paleomagnetism captures paleolatitude. Ocean width changes by reversing sea-floor anomalies.Ocean width changes by reversing sea-floor anomalies. Rock and fossil distributions compare across oceans.Rock and fossil distributions compare across oceans.


Methods for Studying the PastMethods for Studying the Past Paleoclimates – Rocks preserve ancient climates.Paleoclimates – Rocks preserve ancient climates.

Tropical – Extensive coral reefs.Tropical – Extensive coral reefs. Sub-tropical – Extensive deserts. Sub-tropical – Extensive deserts. Polar – Extensive glacial deposits.Polar – Extensive glacial deposits.

Climatic belts expand and contract.Climatic belts expand and contract. Greenhouse Earth.Greenhouse Earth. Snowball earth.Snowball earth.

1818O/O/1616O isotopic ratios preserve O isotopic ratios preserve

ancient temperaturesancient temperatures


Methods for Studying the PastMethods for Studying the Past Evolution – Fossils preserve changes in Earth’s life.Evolution – Fossils preserve changes in Earth’s life.

Sedimentary rocks preserve fossil ecosystems.Sedimentary rocks preserve fossil ecosystems. Organisms inhabiting Earth have obviously changed.Organisms inhabiting Earth have obviously changed.

Over geologic time, most species have exhibited both…Over geologic time, most species have exhibited both… Trends toward specialization.Trends toward specialization. Catastrophic extinctions.Catastrophic extinctions.


The Hadean EonThe Hadean Eon Geochronology dates the age of Earth to 4.57 Ga.Geochronology dates the age of Earth to 4.57 Ga.

Based on ages of meteorites akin to planetesimals.Based on ages of meteorites akin to planetesimals.

Continental crustal rocks date from 3.8 Ga. Continental crustal rocks date from 3.8 Ga. The time between 4.57 – 3.8 Ga is the Hadean Eon.The time between 4.57 – 3.8 Ga is the Hadean Eon.

Named for Hades, the Greek god of the underworld.Named for Hades, the Greek god of the underworld. Began with formation of Earth by planetesimal accretion.Began with formation of Earth by planetesimal accretion.


The Hadean EonThe Hadean Eon Earth was heated by impacts and radioactive decay.Earth was heated by impacts and radioactive decay. Earth was hot enough to partially melt by ~ 4.5 Ga.Earth was hot enough to partially melt by ~ 4.5 Ga.

The molten Earth underwent chemical differentiation.The molten Earth underwent chemical differentiation.Gravity pulled molten iron into the center.Gravity pulled molten iron into the center.The ultramafic mantle remained as a thick shell. The ultramafic mantle remained as a thick shell.


The Hadean EonThe Hadean Eon After differentiation, Earth smashed a proto-planet.After differentiation, Earth smashed a proto-planet. The size of Mars, this planet blasted…The size of Mars, this planet blasted…

A sizeable chunk of Earth’s mantle. A sizeable chunk of Earth’s mantle. Much of the proto-planet’s mantle.Much of the proto-planet’s mantle.

Debris from the collision formed a ring around Earth. Debris from the collision formed a ring around Earth.


The Hadean EonThe Hadean Eon This debris coalesced to form the moon.This debris coalesced to form the moon. When 1When 1stst formed, moon was much closer (20,000 km). formed, moon was much closer (20,000 km). Today it is 19x farther away (384,000 km). Today it is 19x farther away (384,000 km).


The Hadean EonThe Hadean Eon Earth was inhospitable; a molten surface.Earth was inhospitable; a molten surface.

Evidence of solidified igneous rock dates from 4.4 Ga.Evidence of solidified igneous rock dates from 4.4 Ga.This evidence is from zircon grains, not a whole rock.This evidence is from zircon grains, not a whole rock.


The Hadean EonThe Hadean Eon Volcanic outgassing created a deadly atmosphere.Volcanic outgassing created a deadly atmosphere.

NN22, NH, NH33, CH, CH44, H, H22O, CO, COO, CO, CO22 and SO and SO442-2- were components. were components.

This atmosphere had a greater density that today’s.This atmosphere had a greater density that today’s.

Early formed crust was bombarded by meteorites. Early formed crust was bombarded by meteorites. Meteorite impacts were abundant between 4.0 and 3.9 Ga.Meteorite impacts were abundant between 4.0 and 3.9 Ga.

This would have destroyed early formed crust.This would have destroyed early formed crust.Oldest evidence of crust is 4.03 Ga.Oldest evidence of crust is 4.03 Ga.


The Hadean EonThe Hadean Eon The first oceans formed as rain from the skies.The first oceans formed as rain from the skies.

Liquid water required cooling of the surface.Liquid water required cooling of the surface. First evidence of oceans from marine sediments ~ 3.85 Ga.First evidence of oceans from marine sediments ~ 3.85 Ga.


The Archean EonThe Archean Eon Time of significant change to planet Earth.Time of significant change to planet Earth. ~3.8 Ga, Earth had cooled to form lithosphere.~3.8 Ga, Earth had cooled to form lithosphere.

Intense meteorite bombardment ceased. Intense meteorite bombardment ceased. Portions of the rock record begin to survive. Portions of the rock record begin to survive.


The Archean EonThe Archean Eon Had plate tectonics started yet? 2 models.Had plate tectonics started yet? 2 models.

Many small microplates, island arcs and hot spot volcanoes Many small microplates, island arcs and hot spot volcanoes rapidly formed and subducted crust. rapidly formed and subducted crust.

Archean lithosphere was too hot to subduct; hot spot plume Archean lithosphere was too hot to subduct; hot spot plume volcanics dominated formation of crust. volcanics dominated formation of crust.


The Archean EonThe Archean Eon Volume of continental crust increased dramatically.Volume of continental crust increased dramatically.

85% of modern continental area present by end Archean. 85% of modern continental area present by end Archean. Signals full development of plate tectonic processes.Signals full development of plate tectonic processes.


The Archean EonThe Archean Eon How did continental crust form?How did continental crust form?

Low density felsic rocks formed above subduction zones. Low density felsic rocks formed above subduction zones. Felsic crustal blocks grew via continental collision.Felsic crustal blocks grew via continental collision.Felsic sediments accumulated near continental crust. Felsic sediments accumulated near continental crust.

Mantle hot spots built mafic volcanoes.Mantle hot spots built mafic volcanoes.


The Archean EonThe Archean Eon How did continental crust form?How did continental crust form?

Continental crust is too buoyant to subduct.Continental crust is too buoyant to subduct.Jams subduction trenches.Jams subduction trenches.Shuts off subduction.Shuts off subduction.Creates thickened, uplifted continental crust.Creates thickened, uplifted continental crust.

Frequent collisions sutured volcanic arcs, hot spots and Frequent collisions sutured volcanic arcs, hot spots and sedimentary debris together as protocontinents. sedimentary debris together as protocontinents.


The Archean EonThe Archean Eon The 1The 1stst cratons had formed by 2.7 Ga. Cratons are… cratons had formed by 2.7 Ga. Cratons are…

Long-lived blocks of durable continental crust.Long-lived blocks of durable continental crust. Too buoyant to subduct, these blocks persist over time. Too buoyant to subduct, these blocks persist over time.

Cratons are the interior core of modern continents.Cratons are the interior core of modern continents. Continents grow as rocks are added to cratons.Continents grow as rocks are added to cratons.


The Archean EonThe Archean Eon Archean cratons consist of 5 principle rock types.Archean cratons consist of 5 principle rock types.

Gneiss – Hi-grade metamorphics from Archean collisions.Gneiss – Hi-grade metamorphics from Archean collisions. Greenstone – Metamorphosed fragments of mafic rocks.Greenstone – Metamorphosed fragments of mafic rocks. Granite – Magmas from partial melting of the crust.Granite – Magmas from partial melting of the crust. Graywacke – Sedimentary debris derived from arcs.Graywacke – Sedimentary debris derived from arcs. Chert – Silica precipitated in the deep sea. Chert – Silica precipitated in the deep sea.


The Archean EonThe Archean Eon Archean shallow sediments are poorly known. Archean shallow sediments are poorly known.

There were few shallow depositional settings, or…There were few shallow depositional settings, or… Few examples have survived destruction by erosion.Few examples have survived destruction by erosion.

Sedimentary processes were clearly operating.Sedimentary processes were clearly operating. Transport rounded sediment grains. Transport rounded sediment grains.


The Archean EonThe Archean Eon Life first appeared during Life first appeared during

the Archean. Evidence?the Archean. Evidence? Biomarker molecules.Biomarker molecules. Isotopic signatures.Isotopic signatures. Preserved fossil cells. Preserved fossil cells.

Clear evidence of life in Clear evidence of life in rocks dated to 3.5 Ga.rocks dated to 3.5 Ga. Life may have started earlier.Life may have started earlier.

Oldest undisputed bacteria Oldest undisputed bacteria fossils ~ 3.2 Ga.fossils ~ 3.2 Ga.


The Archean EonThe Archean Eon Rocks after 3.2 Ga contain stromatolites.Rocks after 3.2 Ga contain stromatolites.

Layered mats of cyanobacteria (blue-green algae).Layered mats of cyanobacteria (blue-green algae). Sediments stuck to mucous coatings on algal filaments. Sediments stuck to mucous coatings on algal filaments.

Photosynthesis changed Earth’s atmosphere.Photosynthesis changed Earth’s atmosphere. Converts COConverts CO22 and H and H22O to organic matter and free oxygen.O to organic matter and free oxygen.


The Proterozoic EonThe Proterozoic Eon Protero = first; zoic = life.Protero = first; zoic = life.

Named before Archean life was discovered.Named before Archean life was discovered.

~ 2 Ga (2.5 to 0.542 Ga); almost ½ of Earth history.~ 2 Ga (2.5 to 0.542 Ga); almost ½ of Earth history. The unfamiliar Archean world changed to…The unfamiliar Archean world changed to…

Fewer, larger lithospheric plates.Fewer, larger lithospheric plates. Larger continental landmasses.Larger continental landmasses. An oxygenated atmosphere.An oxygenated atmosphere.


The Proterozoic EonThe Proterozoic Eon New continental crust formed, but at slower rates. New continental crust formed, but at slower rates.

90% of Earth’s continental crust by the middle Proterozoic.90% of Earth’s continental crust by the middle Proterozoic. Continents grew by addition of volcanic arcs.Continents grew by addition of volcanic arcs. Continents cooled and strengthened to become cratons.Continents cooled and strengthened to become cratons.


The Proterozoic EonThe Proterozoic Eon Case History: The assembly of North America.Case History: The assembly of North America.

A large area of Pre-Cambrian rocks outcrops in Canada.A large area of Pre-Cambrian rocks outcrops in Canada.This constitutes a shield – a low-lying area of Pre-C rocks.This constitutes a shield – a low-lying area of Pre-C rocks.

The cratonic platform occurs to the S and W of the shield.The cratonic platform occurs to the S and W of the shield.Phanerozoic strata cover the Pre-C shield.Phanerozoic strata cover the Pre-C shield.Shield rock underlies much of U.S.Shield rock underlies much of U.S.

Encountered by drilling.Encountered by drilling. Exposed in the Grand Canyon.Exposed in the Grand Canyon.


The Proterozoic EonThe Proterozoic Eon Canadian Shield consists of many distinct blocks.Canadian Shield consists of many distinct blocks.

Sutured Archean crustal blocks form the shield interior. Sutured Archean crustal blocks form the shield interior. Added volcanic arcs and crustal slivers extended Added volcanic arcs and crustal slivers extended


The Proterozoic EonThe Proterozoic Eon Continental collision created Pre-C supercontinents.Continental collision created Pre-C supercontinents.

Rodinia – Formed ~ 1 Ga.Rodinia – Formed ~ 1 Ga. The Grenville Orogeny formed an extensive mountain belt.The Grenville Orogeny formed an extensive mountain belt.

Pannotia – A short-lived supercontinent ~ 600 Ma.Pannotia – A short-lived supercontinent ~ 600 Ma.


The Proterozoic EonThe Proterozoic Eon Atmospheric oxygen (OAtmospheric oxygen (O22) skyrocketed 2.4 to 2.2 Ga. ) skyrocketed 2.4 to 2.2 Ga.

Currently, OCurrently, O22 is 21% of the atmosphere. is 21% of the atmosphere.

Before 2.2 Ga, detrital pyrite in sediments indicated no OBefore 2.2 Ga, detrital pyrite in sediments indicated no O22. . Redbeds (red from Fe-oxides) don’t appear before 2.2 Ga.Redbeds (red from Fe-oxides) don’t appear before 2.2 Ga. Banded Iron Formations (BIFs) – Fe dissolved in the ocean Banded Iron Formations (BIFs) – Fe dissolved in the ocean

reacted with Oreacted with O22, forming world wide iron oxide deposits. , forming world wide iron oxide deposits.


The Proterozoic EonThe Proterozoic Eon Atmospheric OAtmospheric O22 permitted diversification of life. permitted diversification of life.

Aerobic respiration more efficient; allowed multicellular life.Aerobic respiration more efficient; allowed multicellular life.Without OWithout O22, only single celled organisms possible. , only single celled organisms possible.

Eukaryotic (nucleated) cells evolved by at least 1.0 Ga.Eukaryotic (nucleated) cells evolved by at least 1.0 Ga. The possibility of a land-dwelling biota.The possibility of a land-dwelling biota.

OO22 made formation of the ozone layer possible. made formation of the ozone layer possible. Ozone absorbs deadly ultraviolet (UV) radiation.Ozone absorbs deadly ultraviolet (UV) radiation. Prior to the ozone layer, exposed land was bathed in UV. Prior to the ozone layer, exposed land was bathed in UV.


The Proterozoic EonThe Proterozoic Eon Over the last 500 Ma of the Proterozoic…Over the last 500 Ma of the Proterozoic…

A gigantic leap in biological complexity.A gigantic leap in biological complexity.Simple organisms gave way to complex ones.Simple organisms gave way to complex ones.

Ediacaran fauna – Unusual soft-bodied fossils.Ediacaran fauna – Unusual soft-bodied fossils. Preserved in end Proterozoic sediments. Preserved in end Proterozoic sediments. Multicellular invertebrates Multicellular invertebrates

resembling worms and jellyfish.resembling worms and jellyfish.


The Proterozoic EonThe Proterozoic Eon Ediacaran fauna arose in conjunction with 2 events.Ediacaran fauna arose in conjunction with 2 events.

The assembly and breakup of the Pannotia. The assembly and breakup of the Pannotia. Global cooling possibly resulting in a “Snowball Earth.”Global cooling possibly resulting in a “Snowball Earth.”

Most of the world bears evidence of being frozen.Most of the world bears evidence of being frozen.Life diversified rapidly after snowball conditions waned. Life diversified rapidly after snowball conditions waned.


The Phanerozoic EonThe Phanerozoic Eon Phaneros = visible; zoic = life. Phaneros = visible; zoic = life. The most recent 542 Ma of Earth history.The most recent 542 Ma of Earth history.

Began with appearance of diverse hard-shelled organisms.Began with appearance of diverse hard-shelled organisms.Hard-shells vastly increased fossil preservation.Hard-shells vastly increased fossil preservation.Made possible a more complete archive of life on Earth.Made possible a more complete archive of life on Earth.


The Phanerozoic EonThe Phanerozoic Eon The Phanerozoic is divided into 3 Eras.The Phanerozoic is divided into 3 Eras.

Paleozoic – Ancient life. Paleozoic – Ancient life. Mesozoic – Middle life.Mesozoic – Middle life. Cenozoic – Recent life. Cenozoic – Recent life.

Eras emphasize changes in Earth’s biota. Eras emphasize changes in Earth’s biota.


The Phanerozoic EonThe Phanerozoic Eon Tectonic plates and continental blocks rearranged.Tectonic plates and continental blocks rearranged.

Ancient changes in paleogeography have been deciphered.Ancient changes in paleogeography have been deciphered. The map of Earth looked different throughout the Eon.The map of Earth looked different throughout the Eon.

New supercontinents formed and rifted apart.New supercontinents formed and rifted apart. Numerous orogenic belts were created and eroded.Numerous orogenic belts were created and eroded.


The Phanerozoic EonThe Phanerozoic Eon Phanerozoic sea-level (SL) has changed often.Phanerozoic sea-level (SL) has changed often. SL highstands flooded continental interiors.SL highstands flooded continental interiors.

Rising SL (transgression) initiated sediment deposition. Rising SL (transgression) initiated sediment deposition.

SL lowstands exposedSL lowstands exposed

continental margins.continental margins. Falling SL (regression) Falling SL (regression)

initiated erosion or initiated erosion or

non-deposition.non-deposition.


The Phanerozoic EonThe Phanerozoic Eon SL cycles are marked by large-scale unconformities.SL cycles are marked by large-scale unconformities. Stratigraphic sequences reflect SL highstands. Stratigraphic sequences reflect SL highstands.

Rising SL invaded further inland with passing time.Rising SL invaded further inland with passing time. Falling SL moved progressively outward from the interior. Falling SL moved progressively outward from the interior. Unconformities… Unconformities…

Become younger toward Become younger toward

continental interiors.continental interiors.Bound less time in theBound less time in the

interior; more time along interior; more time along

the margins.the margins.


The Early PaleozoicThe Early Paleozoic Cambrian and Ordovician Paleogeography:Cambrian and Ordovician Paleogeography:

Rifting of Pannotia left 4 large continental fragments.Rifting of Pannotia left 4 large continental fragments.Gondwana – (S. America, Africa, Antarctica, India, Australia).Gondwana – (S. America, Africa, Antarctica, India, Australia).Laurentia – (N. America and Greenland).Laurentia – (N. America and Greenland).Baltica – (Europe).Baltica – (Europe).Siberia.Siberia.

Part of Gondwana wasPart of Gondwana was

over the South Pole over the South Pole

in the late Ordovician.in the late Ordovician.Marked by glacial deposits.Marked by glacial deposits.



The rifted continents developed passive margins.The rifted continents developed passive margins. Rising seas flooded expanses of continental crust.Rising seas flooded expanses of continental crust.

Epicontinental seas were shallow, warm and sunlit.Epicontinental seas were shallow, warm and sunlit.Thriving marine life preserved as fossiliferous sediments.Thriving marine life preserved as fossiliferous sediments.



Subduction carried a volcanic arc toward Laurentia. Subduction carried a volcanic arc toward Laurentia. Mid-Late Ordovician: continental crust jammed the trench.Mid-Late Ordovician: continental crust jammed the trench. Passive margin sediments were deformed by the collision.Passive margin sediments were deformed by the collision. A volcanic arc was welded onto the margin.A volcanic arc was welded onto the margin. The “Taconic Orogeny” was the 1The “Taconic Orogeny” was the 1stst Appalachian event. Appalachian event.


The Early PaleozoicThe Early Paleozoic Cambrian and Ordovician Life Evolution: Cambrian and Ordovician Life Evolution:

Earliest Cambrian – Hard shells appeared for the 1Earliest Cambrian – Hard shells appeared for the 1stst time. time. Massive diversification followed: the “Cambrian explosion.” Massive diversification followed: the “Cambrian explosion.” Reflects the evolution of a complex ecosystem.Reflects the evolution of a complex ecosystem.

Plankton, deposit feeders, giant predators. Plankton, deposit feeders, giant predators.


The Early PaleozoicThe Early Paleozoic Cambrian and Ordovician Life Evolution: Cambrian and Ordovician Life Evolution:

Life during the Ordovician included several “firsts.”Life during the Ordovician included several “firsts.”The 1The 1stst vertebrates were jawless fish (agnathans). vertebrates were jawless fish (agnathans).The 1The 1stst crinoids (flower-like echinoderms). crinoids (flower-like echinoderms).The 1The 1stst green algae and primitive land plants. green algae and primitive land plants.

The end of the Ordovician witnessed a mass extinction.The end of the Ordovician witnessed a mass extinction. The seas roiled with life, but there was no life on land yet.The seas roiled with life, but there was no life on land yet.


The Middle PaleozoicThe Middle Paleozoic Silurian and Devonian Paleogeography: Silurian and Devonian Paleogeography:

Silurian climate warmed to create greenhouse conditions.Silurian climate warmed to create greenhouse conditions.Epicontinental seas expanded.Epicontinental seas expanded.

Gigantic reef complexes developed in normal salinity water.Gigantic reef complexes developed in normal salinity water. Thick evaporite deposits accumulated in isolated ocean basins.Thick evaporite deposits accumulated in isolated ocean basins.

The Taconic mountains eroded away.The Taconic mountains eroded away.Sediment was shed to either side of the eroding source. Sediment was shed to either side of the eroding source.



A 2A 2ndnd eastern orogenic phase occurred in the Devonian. eastern orogenic phase occurred in the Devonian.The Avalon microcontinent was welded onto North America. The Avalon microcontinent was welded onto North America. Large mountains marked the Acadian-Caledonian Orogeny.Large mountains marked the Acadian-Caledonian Orogeny.Vast sediment aprons spread outward from the uplift.Vast sediment aprons spread outward from the uplift.



In the west, thick passive-margin sediments accumulated.In the west, thick passive-margin sediments accumulated.An island arc smashed this margin in the Late Devonian.An island arc smashed this margin in the Late Devonian.This created the Antler orogenic belt. This created the Antler orogenic belt.


The Middle PaleozoicThe Middle Paleozoic Silurian and Devonian Life Evolution:Silurian and Devonian Life Evolution:

New species replaced those lost to extinction.New species replaced those lost to extinction. Vascular land plants evolved and spread across Earth. Vascular land plants evolved and spread across Earth.

Internal water transport systems. Internal water transport systems. Woody tissues.Woody tissues.Seeds. Seeds.

Land plants changed Earth. Land plants changed Earth.



Fish rapidly evolve and proliferate.Fish rapidly evolve and proliferate.Jawed fish.Jawed fish.Boney fish.Boney fish.

The 1The 1stst land animals land animals

followed plants.followed plants.Scorpions.Scorpions.Spiders.Spiders. Insects.Insects.Crustaceans.Crustaceans.



At the end Devonian, the 1At the end Devonian, the 1stst amphibians appeared. amphibians appeared.Walked on legs. Walked on legs. Breathed air with lungs. Breathed air with lungs.


The Late PaleozoicThe Late Paleozoic Carboniferous and Permian Paleogeography:Carboniferous and Permian Paleogeography:

Climatic cooling followed the Mid-Paleozoic greenhouse.Climatic cooling followed the Mid-Paleozoic greenhouse. Seas regressed from continents.Seas regressed from continents. Clastics choked out carbonates. Clastics choked out carbonates. Thick coals formed equatorially. Thick coals formed equatorially. Ice sheets spread across Gondwana. Ice sheets spread across Gondwana.



Continental collisions formed the supercontinent Pangaea.Continental collisions formed the supercontinent Pangaea. Gondwana collided with Laurentia (Alleghenian orogeny). Gondwana collided with Laurentia (Alleghenian orogeny).

North America collided with Africa.North America collided with Africa.The Gulf Coast collided with The Gulf Coast collided with

South America.South America. Collisions were oblique.Collisions were oblique.

Folding.Folding.Thrust faulting.Thrust faulting.Strike-slip faulting.Strike-slip faulting.



The Appalachians preserve several types of geology.The Appalachians preserve several types of geology.Thin-skinned thrust faulting over basement rock.Thin-skinned thrust faulting over basement rock.

Produced the Appalachian fold-thrust belt (Valley and Ridge).Produced the Appalachian fold-thrust belt (Valley and Ridge). Deformation above a large horizontal detachment fault.Deformation above a large horizontal detachment fault.

A more intensely deformed and intruded metamorphic core.A more intensely deformed and intruded metamorphic core.



The assembly of Pangaea had other tectonic effects.The assembly of Pangaea had other tectonic effects.Deformation was transmitted across Laurentia.Deformation was transmitted across Laurentia.

Basins and uplifts formed in the mid-continent.Basins and uplifts formed in the mid-continent.

Hercynian orogen - Africa Hercynian orogen - Africa

collided with S. Europe.collided with S. Europe.Ural Mountains – Europe Ural Mountains – Europe

collided with Siberia.collided with Siberia.China attached to China attached to

southern Siberia.southern Siberia.



Pangaea was a massive supercontinent.Pangaea was a massive supercontinent.The interior was a vast desert far from ocean moisture.The interior was a vast desert far from ocean moisture.

Large deposits of red (oxidized) dune and fluvial sandstones.Large deposits of red (oxidized) dune and fluvial sandstones. Large accumulations of evaporites.Large accumulations of evaporites.


The Late PaleozoicThe Late Paleozoic Carboniferous and Permian Life Evolution:Carboniferous and Permian Life Evolution:

Life continued to evolve.Life continued to evolve.Dense tropical wetlands hosted vegetation and giant insects.Dense tropical wetlands hosted vegetation and giant insects.Amphibians diversified. Amphibians diversified. Reptiles appeared for the 1Reptiles appeared for the 1stst time. time.

The amniote egg permitted reproduction away from water. The amniote egg permitted reproduction away from water. Reptiles populated previously inhospitable environments.Reptiles populated previously inhospitable environments.


The Late PaleozoicThe Late Paleozoic Carboniferous and Permian Life Evolution:Carboniferous and Permian Life Evolution:

The Paleozoic ended with the Permian extinction.The Paleozoic ended with the Permian extinction.90% of all marine species disappeared.90% of all marine species disappeared.Some evidence links the extinction to a bolide impact.Some evidence links the extinction to a bolide impact.


Early and Mid-Mesozoic EraEarly and Mid-Mesozoic Era Triassic and Jurassic Paleogeography:Triassic and Jurassic Paleogeography:

The supercontinent Pangaea lasted 100 million years.The supercontinent Pangaea lasted 100 million years. Pangaea began to rift late Triassic to early Jurassic.Pangaea began to rift late Triassic to early Jurassic.

Rifting started in the North Atlantic. Rifting started in the North Atlantic. A thin narrow ocean had A thin narrow ocean had

opened by the end Jurassic.opened by the end Jurassic.This basin accumulated This basin accumulated

thick evaporite deposits.thick evaporite deposits.



Pangaea's interior was hot and dry.Pangaea's interior was hot and dry. Greenhouse climates cooled by the mid-Jurassic.Greenhouse climates cooled by the mid-Jurassic.

Transgression flooded much of the Rocky Mountain region.Transgression flooded much of the Rocky Mountain region.



Western North America was an active margin. Western North America was an active margin. Subduction created island arcs.Subduction created island arcs.Collision added arcs and Collision added arcs and

microcontinents to N. America.microcontinents to N. America. Sonoma orogeny – Perm – Tri.Sonoma orogeny – Perm – Tri. Nevadan orogeny – Late Jur.Nevadan orogeny – Late Jur.


Early and Mid-Mesozoic EraEarly and Mid-Mesozoic Era Triassic and Jurassic Life Evolution:Triassic and Jurassic Life Evolution:

New species filled niches vacated by extinction.New species filled niches vacated by extinction.Corals became dominant reef builders. Corals became dominant reef builders. Gymnosperms proliferated.Gymnosperms proliferated.Reptiles diversified. Reptiles diversified.

Plesiosaurs – Swimming reptiles.Plesiosaurs – Swimming reptiles. Pterosaurs – Flying reptiles. Pterosaurs – Flying reptiles. Turtles appear.Turtles appear.



By end of the Triassic the first true at dinosaurs appeared. By end of the Triassic the first true at dinosaurs appeared. Dinosaurs differ from other reptiles in significant ways. Dinosaurs differ from other reptiles in significant ways.

Legs are positioned beneath their bodies.Legs are positioned beneath their bodies.They bear evidence of warm bloodedness. They bear evidence of warm bloodedness.

By the end Jurassic giant sauropods were abundant. By the end Jurassic giant sauropods were abundant.



The 1The 1stst feathered birds (archaeopteryx). feathered birds (archaeopteryx). The 1The 1stst ancestors of mammals appeared at Triassic. ancestors of mammals appeared at Triassic.

They resembled small rat like creatures. They resembled small rat like creatures.


The Late MesozoicThe Late Mesozoic Cretaceous Paleogeography:Cretaceous Paleogeography:

Climate continued to warm; seas flooded the continents.Climate continued to warm; seas flooded the continents.An ocean connected the An ocean connected the

Gulf of Mexico to the Arctic. Gulf of Mexico to the Arctic. Epicontinental seas Epicontinental seas

accumulated limestone accumulated limestone

and sandstone.and sandstone.



Breakup of Pangaea continued through the Cretaceous.Breakup of Pangaea continued through the Cretaceous.South America separated from Africa.South America separated from Africa.Antarctica separated from Australia. Antarctica separated from Australia. India broke from India broke from

Gondwana and raced Gondwana and raced

toward Asia.toward Asia.Passive margins Passive margins

developed along developed along

the Atlantic. the Atlantic.



In western North America the Sierran continental arc grew.In western North America the Sierran continental arc grew.Arc volcanoes have long eroded away.Arc volcanoes have long eroded away.Roots of the arc are exposed as the Sierra Nevada batholith.Roots of the arc are exposed as the Sierra Nevada batholith.An accretionary prism grew on the overriding plate. An accretionary prism grew on the overriding plate. These sediments form the present day Coast Range. These sediments form the present day Coast Range.


The Late MesozoicThe Late Mesozoic Cretaceous Cretaceous

Paleogeography:Paleogeography: Sierran Arc compression Sierran Arc compression

initiated the Sevier orogeny. initiated the Sevier orogeny. Large thrust faults moved to Large thrust faults moved to

the east of the arc. the east of the arc. The Sevier fold and thrust The Sevier fold and thrust

belt elevated the Canadian belt elevated the Canadian Rockies.Rockies.

A large foreland basin A large foreland basin formed east of the thrusting.formed east of the thrusting.



Laramide Orogeny – Late Cretaceous basement uplifts.Laramide Orogeny – Late Cretaceous basement uplifts.Reverse faulting due to continued compression to the west. Reverse faulting due to continued compression to the west. Uplifts appear in Wyoming, Colorado, Utah and Arizona. Uplifts appear in Wyoming, Colorado, Utah and Arizona.

Basement faulting folded overlying Paleozoic strata. Basement faulting folded overlying Paleozoic strata. Results: Large monoclines and uplift of Rocky Mountain Front.Results: Large monoclines and uplift of Rocky Mountain Front.


The Late MesozoicThe Late Mesozoic Orogenic events suggest complicated feedbacks. Orogenic events suggest complicated feedbacks. Rifting of Pangaea led to mid-ocean ridges (MORs).Rifting of Pangaea led to mid-ocean ridges (MORs). Seafloor spreading operated 3x faster. Seafloor spreading operated 3x faster. Huge submarine plateaus formed from flood basalt. Huge submarine plateaus formed from flood basalt.


The Late MesozoicThe Late Mesozoic The Late K was a time of unusual volcanic activity.The Late K was a time of unusual volcanic activity. Attributed to unusually large hot spots.Attributed to unusually large hot spots. Late K volcanism influenced the climate.Late K volcanism influenced the climate.

Volcanic COVolcanic CO22 (8x modern values) warmed the atmosphere. (8x modern values) warmed the atmosphere. Melting ice caps contributing to sea level rise. Melting ice caps contributing to sea level rise.


The Late MesozoicThe Late Mesozoic Cretaceous Life Evolution:Cretaceous Life Evolution:

Teleost fish appeared and became dominant.Teleost fish appeared and became dominant.Symmetrical tails, specialized fins, short jaws, rounded scales.Symmetrical tails, specialized fins, short jaws, rounded scales.

Swimming reptiles and gigantic turtles swam the seas.Swimming reptiles and gigantic turtles swam the seas. Angiosperms (flowering plants) appeared and spread.Angiosperms (flowering plants) appeared and spread.

Produce seeds rapidly.Produce seeds rapidly. Insects facilitate pollination. Insects facilitate pollination. Hardwood trees proliferated. Hardwood trees proliferated.


The Late MesozoicThe Late Mesozoic Cretaceous Life Evolution:Cretaceous Life Evolution:

Dinosaurs reached their evolutionary peak.Dinosaurs reached their evolutionary peak. Inhabited almost all environments on earth. Inhabited almost all environments on earth. Social herds of grazing dinosaurs roamed the plains. Social herds of grazing dinosaurs roamed the plains. Large carnivores fed upon the herbivores. Large carnivores fed upon the herbivores. Pterosaurs soared overhead, birds began to diversify. Pterosaurs soared overhead, birds began to diversify.

Mammals developed larger brains and specialized teeth. Mammals developed larger brains and specialized teeth.


The Late MesozoicThe Late Mesozoic The K-T (Cretaceous–Tertiary) boundary event.The K-T (Cretaceous–Tertiary) boundary event.

There is abundant evidence of catastrophic change. There is abundant evidence of catastrophic change. Instantaneous global change in fossil assemblages. Instantaneous global change in fossil assemblages. Sudden mass extinction of most species on earth. Sudden mass extinction of most species on earth.

The dinosaurs which had ruled the planet for 150 Ma vanished. The dinosaurs which had ruled the planet for 150 Ma vanished. 90 percent of plankton disappeared.90 percent of plankton disappeared. 75% of plant species vanished. 75% of plant species vanished.



Catastrophic impact by a 10 km comet or meteorite. Catastrophic impact by a 10 km comet or meteorite. The Chicxulub crater lies beneath the northern Yucatan.The Chicxulub crater lies beneath the northern Yucatan.

Radiometric dating indicates the crater formed at ~ 65 Ma.Radiometric dating indicates the crater formed at ~ 65 Ma.100 km wide; 16 km deep. 100 km wide; 16 km deep.

Periodic impacts are Periodic impacts are

likely contributors to likely contributors to

other extinctions. other extinctions.



Evidence for an impact end to the Mesozoic?Evidence for an impact end to the Mesozoic?Thin clay interrupts deep-sea chalk at the K-T boundary. Thin clay interrupts deep-sea chalk at the K-T boundary.

This suggests that, for a short time, all plankton died.This suggests that, for a short time, all plankton died. Iridium in the clay is rare on Earth; common in meteorites. Iridium in the clay is rare on Earth; common in meteorites. Iridium enriched clay found at the K-T boundary worldwide.Iridium enriched clay found at the K-T boundary worldwide. The clay contains shocked quartz and tiny glass spheres. The clay contains shocked quartz and tiny glass spheres.

An immense impact best explains these features. An immense impact best explains these features.


The Late MesozoicThe Late Mesozoic The K-T (Cretaceous–Tertiary) boundary event. The K-T (Cretaceous–Tertiary) boundary event.

What did the impact do to Earth?What did the impact do to Earth?The impact blasted debris into the sky from a huge crater.The impact blasted debris into the sky from a huge crater. It created a gigantic tsunami (2 km high). It created a gigantic tsunami (2 km high). The blast of hot air set forests on fire. The blast of hot air set forests on fire.


The Late MesozoicThe Late Mesozoic The K-T (Cretaceous–Tertiary) boundary event. The K-T (Cretaceous–Tertiary) boundary event.

What did the impact do to Earth?What did the impact do to Earth?Dust in the atmosphere would have blotted out the sun. Dust in the atmosphere would have blotted out the sun. Sulfate from vaporized gypsum created sulfuric acid rain. Sulfate from vaporized gypsum created sulfuric acid rain. Lack of sunlight shut down photosynthesis.Lack of sunlight shut down photosynthesis.


The Cenozoic EraThe Cenozoic Era Cenozoic (65 Ma-present) – The most recent history.Cenozoic (65 Ma-present) – The most recent history. Cenozoic Paleogeography:Cenozoic Paleogeography:

During the last 65 Ma, Earth has continued to change.During the last 65 Ma, Earth has continued to change. The final stages of the breakup of Pangaea.The final stages of the breakup of Pangaea.

Australia detached from Antarctica.Australia detached from Antarctica.Greenland separated from North AmericaGreenland separated from North AmericaThe North Sea formed between Britain and Europe. The North Sea formed between Britain and Europe. Sea-floor spreading continued to open the Atlantic Ocean.Sea-floor spreading continued to open the Atlantic Ocean.


The Cenozoic EraThe Cenozoic Era Cenozoic Paleogeography:Cenozoic Paleogeography:

Fragments of Gondwana collided with Europe and Asia.Fragments of Gondwana collided with Europe and Asia.Closed the Tethys Ocean.Closed the Tethys Ocean.Deformed and uplifted the Alpine-Himalayan chain. Deformed and uplifted the Alpine-Himalayan chain.



Pacific margins of the Americas continued convergence.Pacific margins of the Americas continued convergence.Andes grew as a continental volcanic arc. Andes grew as a continental volcanic arc. Rocky Mountains grew by thrusting and basement uplift. Rocky Mountains grew by thrusting and basement uplift.



The large Farallon plate was almost completely consumed. The large Farallon plate was almost completely consumed. A transform fault replaced part of the Farallon trench 40 Ma. A transform fault replaced part of the Farallon trench 40 Ma. The San Andreas / Queen Charlotte fault system formed. The San Andreas / Queen Charlotte fault system formed. The Juan de Fuca plate remains as a Farallon remnant. The Juan de Fuca plate remains as a Farallon remnant.



East-west extension started to East-west extension started to stretch southwestern N. Am.stretch southwestern N. Am.A broad continental rift stretched A broad continental rift stretched

and thinned the crust.and thinned the crust.This region is called the Basin This region is called the Basin

and Range Province. and Range Province. Elongate N-S linear mountain Elongate N-S linear mountain

ridges (ranges). ridges (ranges). Ranges are separated by N-S Ranges are separated by N-S

linear valleys (basins). linear valleys (basins). This geometry reflects normal This geometry reflects normal

fault block rotation. fault block rotation.



Global climate has gradually cooled since the Cretaceous.Global climate has gradually cooled since the Cretaceous. The Antarctic ice cap reappeared in the early Oligocene.The Antarctic ice cap reappeared in the early Oligocene. Continued cooling led to the formation of grasslands.Continued cooling led to the formation of grasslands. The Isthmus of Panama emerged 2.5 Ma. The Isthmus of Panama emerged 2.5 Ma.

Isolated circulation between the Atlantic and the Pacific.Isolated circulation between the Atlantic and the Pacific.Permitted the Arctic Ocean to freeze. Permitted the Arctic Ocean to freeze.



The Quaternary Period (2 Ma – present): Cool climate.The Quaternary Period (2 Ma – present): Cool climate.Pleistocene ice ages – Continental scale glaciation.Pleistocene ice ages – Continental scale glaciation.

Glaciers have advanced and Glaciers have advanced and

retreated at least 20 times. retreated at least 20 times. Modern landscapes sculpted Modern landscapes sculpted

by glacial erosion /deposition.by glacial erosion /deposition. Climate warmed 11 Ka; Earth Climate warmed 11 Ka; Earth

is currently in an interglacial. is currently in an interglacial.



The Quaternary Period (2 Ma – present): Cool climate.The Quaternary Period (2 Ma – present): Cool climate.Pleistocene ice ages – Continental scale glaciation.Pleistocene ice ages – Continental scale glaciation.

During ice ages,During ice ages,

SL fell exposing SL fell exposing

continental shelves. continental shelves. Shelves acted as Shelves acted as

land bridges for land bridges for

human and animal human and animal

migration. migration.


The Cenozoic EraThe Cenozoic Era Cenozoic Life Evolution:Cenozoic Life Evolution:

After the K-T boundary, plant life recovered.After the K-T boundary, plant life recovered. Forests of angiosperms and gymnosperms reappeared.Forests of angiosperms and gymnosperms reappeared. The 1The 1stst grasses appeared in the middle Cenozoic. grasses appeared in the middle Cenozoic. Dinosaur descendants (birds) diversified and spread.Dinosaur descendants (birds) diversified and spread.



The Cenozoic is known as the age of mammals. The Cenozoic is known as the age of mammals. Mammals rapidly diversified to fill vacated niches. Mammals rapidly diversified to fill vacated niches. By mid-Cenozoic huge mammals appeared.By mid-Cenozoic huge mammals appeared.

Woolly mammoths.Woolly mammoths.Giant beavers.Giant beavers.Ground sloths. Ground sloths.

Late Cenozoic, human ancestors 1Late Cenozoic, human ancestors 1stst appeared. appeared.



Ape-like primates diversified in Ape-like primates diversified in the Miocene (~ 20 Ma).the Miocene (~ 20 Ma).

The 1The 1stst human-like primate human-like primate appeared about 4 Ma. appeared about 4 Ma.

The first members of the genus The first members of the genus Homo appeared to 2.4 Ma. Homo appeared to 2.4 Ma.



What sparked the evolution of the genus Homo? What sparked the evolution of the genus Homo? Climate changes that led to the spread of grasslands?Climate changes that led to the spread of grasslands?

Permitted departure from the trees. Permitted departure from the trees. Life on the ground allowed more time for infant development.Life on the ground allowed more time for infant development. This permitted growth of larger brains. This permitted growth of larger brains.

Homo erectus appeared ~ 1.6 Ma. Homo erectus appeared ~ 1.6 Ma. Made stone axes.Made stone axes.

Homo sapiens appeared ~ 500 Ka. Homo sapiens appeared ~ 500 Ka. Modern humans appeared ~150 Ka.Modern humans appeared ~150 Ka. Many giant mammals died off 10 Ka.Many giant mammals died off 10 Ka.

Climatic change?Climatic change?Hunting pressure by humans? Hunting pressure by humans?


The Geologic Time ScaleThe Geologic Time Scale

W. W. Norton & CompanyW. W. Norton & CompanyIndependent and Employee-OwnedIndependent and Employee-Owned

This concludes the Norton Media LibraryThis concludes the Norton Media LibraryPowerPoint Slide Set for PowerPoint Slide Set for Chapter 13

Earth: Portrait of a PlanetEarth: Portrait of a Planet

33rdrd Edition (2008) Edition (2008)

by Stephen Marshakby Stephen Marshak


op ch13 lecture_earth3, understanding of earth history,

Education

biography of earth

molten earth

age of earth

formation of earth

greenhouse earth

snowball earth

past earth history

hadean eon earth