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11/10/2011

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Hewitt/Lyons/Suchocki/Yeh

Conceptual Integrated Science

Chapter 26 EARTH'S HISTORY

· · · · · · · ·

History of Earth Science How the rock record reveals Earth's history g The methods used to determine rocks' age The construction of the geologic time scale The evolution of Earth's atmosphere How life evolved through time Plate tectonics and its role in evolution When and how different mountains formed

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Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

A Model of Earth's History

· Earth is ~4.5 billion years old. · Compared to a single calendar year:

--Formation of Earth F i fE h --Oldest rocks --Bacterial life --Dinosaurs --Homo sapiens --Human history Jan. 1 J Feb. 26 Mar. 23 Dec. 14 to 26 Dec. 31 @11:50 pm Dec. 31 @11:59 pm

A Model of Earth's History · Geologic Time--from Earth's formation to the present. · Thi hi t This history i recorded i th rocks of is d d in the k f Earth's crust.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

Uniformitarianism vs. Catastrophism

Catastrophism--Earth's present state is the result of sudden, short-lived, violent events.

· Implies a you g Earth (c eat o ~4000 BC) p es young a t (creation 000 C)

Earth's History

The most fundamental principle in geology is Uniformitarianism: The present is the key to the past. The processes and laws (physics, chemistry, biology, etc.) that operate today are the same as those that have operated in the past.

Uniformitarianism--Earth is the result of slow processes over long periods of time.

· Implies an old Earth (~4.5 billion years), dynamic and everchanging.

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Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

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The Rock Record

The rock record is like a very long, old book with many pages that are tattered, torn, indecipherable, and missing. Two methods of dating rock:

· Relative dating--relative age, the ordering of rocks in sequence by comparative ages · Radiometric dating--absolute age, actual age of rock determined in a laboratory

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Principles of Relative Dating

Original horizontality: · New layers of sediment are horizontally laid down over older layers. Superposition: · In undeformed sequences of rock, top layers are younger than bottom layers. Cross-cutting: · A fault or intrusion that cuts into a rock is younger than the rock it cuts through.

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Principles of Relative Dating

Inclusion: · Any inclusion is older than the rock containing it. Faunal succession: F l i · Fossil organisms follow one another in a definite, irreversible time sequence.

Radiometric Dating

Radiometric dating gives the actual age of a rock by measuring the ratio of radioactive isotopes to their daughter products. This does not work for Sedimentary and some Metamorphic rocks ­ Why? Half-life--the time it takes for half of the parent isotopes to decay to their daughter products.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

Geologic Time

The geologic time scale--a "calendar" of Earth history. · Originally created using relative dates · Specific dates using radiometric dating · Subdivides geologic history into units

-- Eons, eras, periods, and epochs based on changes in life forms

Precambrian Time

The Precambrian ranges from 4.5 billion years ago to ~542 million years ago. · ~90% of Earth's history · Considerable volcanic activity · M t it bombardment Meteorite b b d t · Cyanobacteria · Soft-bodied organisms · Primitive atmosphere and ocean · Beginnings of lithospheric plate formation and movement

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Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

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Precambrian Time

Precambrian fossils: · Most common are stromatolites

--Material deposited by algae --Microfossils of bacteria and algae --Importance of cyanobacteria Importance

Transformation of Earth's Atmosphere

First atmosphere--primarily hydrogen and helium Second atmosphere: · Volcanic outgassing and cometary impacts · Rich in CO2 and H2O, no free oxygen · H2O condensed to form oceans Third atmosphere: · Removal of CO2 to rocks · Nitrogen increase · Oxygen increase (photosynthesis) · Development of O3

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· Plant fossils--middle Precambrian · Primitive animal fossils--late Precambrian · Diverse and multicelled organisms existed by the close of the Precambrian

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Paleozoic Era

Spans ~300 million years.

· Six periods--Each period characterized by changes in life forms and tectonics.

Cambrian Period--542 to 490 Ma

The "Cambrian explosion"--great diversity of life forms evolved during this time.

Characterized by rise and fall of sea level. Shallow seas covered the continents. continents Marine life flourished. Changing sea levels contributed to diversification of life forms. Hard-bodied organisms.

Hard bodied Hard-bodied organisms:

--Ability of organisms to secrete calcium carbonate and calcium phosphate for formation of an outer skeleton.

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Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

Ordovician Period--490 to 443 Ma

Abundant and diverse marine life:

· Emergence of vertebrates (e.g., jawless fishes)

Silurian Period--443 to 417 Ma

Many landmasses joining together as southern continent of Gondwanaland:

· Africa, South America, India, Australia, Antarctica · Situated close to South Pole

Many landmasses on journey to become y j y southern continent of Gondwanaland:

· Situated close to South Pole · Widespread glaciation · Sea level drops

--Shallow-water invertebrates deprived of habitat

Ancestral North America a d Europe beg cest a o t e ca and u ope begin convergence and are situated near equator

· Continents flooded by periodic shallow seas

--Formation of many evaporite beds

Terrestrial life

· Plants, scorpions, and millipedes

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Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

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Devonian Period--417 to 354 Ma

Gondwanaland completely formed in Southern Hemisphere North America and Eurasia joined as continent of Laurasia in Northern Hemisphere Devonian known as "age of fishes"

· Two groups of bony fishes: -- Lung fish -- Lobe-finned fish, which evolved to become the amphibians

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Carboniferous Period--354 to 290 Ma

Warm moist climate Dense swamplands

· Present-day coal beds

Insects Amniote egg Collision of Gondwanaland with Laurasia

· Appalachian Mountains · Ural Mountains

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Permian Period--290 to 248 Ma

Amniote vertebrates continue to diversify

· Ancestral link to reptiles and mammals

Mesozoic Era

Mesozoic era spans ~180 million years from 248 Ma to about 65 Ma Three Periods · Triassic, Jurassic, Cretaceous Often called the "age of reptiles"

Permian extinction

· ~90% of all marine species · ~70% of all land species

Possible causes of extinction

· Volcanic activity in Siberia

--Blocked solar radiation

· Formation of Pangaea

--Lowering of sea level

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

Mesozoic Era

Mesozoic history:

· Begins with much of the world's land above sea level · Seas invade western North America · Breakup of Pangaea begins forming the Atlantic Ocean · North American plate began to override the Pacific plate · Mountains of western North America began forming

Mesozoic Era

Mesozoic life Survivors of the great Paleozoic extinction:

· True pines and redwoods · Flo ering plants Flowering · Insects · Reptiles (first true terrestrial animals) readily adapt to the dry Mesozoic climate · Reptiles have shell-covered eggs that can be laid on the land

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Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

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Mesozoic Era

Mesozoic life:

· Dinosaurs dominated. · One group of reptiles led to the birds. · Many reptile g p along with many other y p groups, g y animal groups, become extinct at the close of the Mesozoic.

-- One hypothesis is that a large asteroid or comet struck Earth. -- Another possibility is that extensive volcanism occurred.

Cenozoic Era

Cenozoic--a smaller fraction of geologic time than the Paleozoic or Mesozoic · 65 million years ago to the present · Often called the "age of mammals" · Two Periods:

· Tertiary · Quaternary

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Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

Cenozoic Era

North America: Most of the continent was above sea level throughout the Cenozoic era. Western North America:

· Mountain building volcanism and building, volcanism, earthquakes · Large region uplifted--Basin and Range province is formed, Rockies are re-elevated, rivers erode the Grand and Black canyons, volcanic activity is abundant · San Andreas Fault

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Cenozoic Era

Eastern North America:

· Stable with abundant marine sedimentation · Eroded Appalachians raised by isostatic adjustments

Eurasia:

· Africa­Arabia collision produces Alps · India with Asia produce the Himalayas

Worldwide:

· Climates cooled · Glaciation in temperate zones · One-third of the land covered by ice

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Cenozoic Era

Cenozoic life: Mammals replaced reptiles as the dominant land animals. Flowering plants dominated the plant world:

· Strongly influenced the evolution of both birds and mammals · Food source for both birds and mammals

Cenozoic Era

Cenozoic life: · Mammals diversified quite rapidly, and some groups become very large:

-- e.g., hornless rhinoceros, which stood nearly 16 feet high -- Many large animals became extinct

· Humans evolve

-- And dominate

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Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

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