eoo lecture ch01
TRANSCRIPT
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CHAPTER 1
Introduction to Planet Earth
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Overview
The world ocean is the most prominent
feature on Earth.
Oceans cover 70.8% of Earths surface.
The origin and development of life on
Earth is connected to the ocean.
The oceans have a long history on Earth.
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Earths Oceans
Earth has one ocean.
It is divided into four
principle oceans, and
one other. Pacific Ocean
Atlantic Ocean
Indian Ocean
Arctic Ocean
Southern, orAntarctic
Ocean
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Earths Oceans
Pacific Ocean
Worlds largest ocean
Accounts for more than half of Earths ocean
space
Worlds deepest ocean
Earths largest geographic feature
Named in 1520 by Ferdinand Magellan
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Earths Oceans
Atlantic Ocean
Half the size of the Pacific Ocean
Shallower than the Pacific Ocean
Separates the Old World from the New World
Indian Ocean
Smaller than the Atlantic Ocean Similar depth as the Atlantic Ocean
Primarily in the Southern Hemisphere
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Earths Oceans
Arctic Ocean
Seven percent the size of the Pacific Ocean
Shallowest world ocean
Permanent layer of sea ice a few meters thick
Southern Ocean orAntarctic Ocean
Circumnavigates Antarctica
Is really the parts of the Pacific, Atlantic, andIndian Oceans that lie south of 50S latitude
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The Seven Seas
Smaller and shallower than oceans
Salt water
Usually enclosed by land
Sargasso Sea defined by surrounding ocean
currents
Directly connected to the ocean
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The Seven Seas
Before the 15th Century, Europeansconsidered the seven seas to be thefollowing:
1. Red Sea2. Mediterranean Sea
3. Persian Gulf
4. Black Sea5. Adriatic Sea
6. Caspian Sea
7. Indian Ocean
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Early Exploration of the Oceans
Early explorers used boats to seek new
fishing grounds for food.
The ocean facilitated trade and interaction
between cultures.
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Pacific Navigators
The peopling of the
Pacific Islands
required extensive
travel in open boatsand exceptional
navigation skills.
It was difficult
because islands arewidely scattered.
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Pacific People
No written records exist of Pacific human
history before the 16th Century.
Archeological evidence suggests island
occupation by people from New Guinea as
early as 40005000 B.C.
Thor Heyerdahl sailed on a balsa raftthe
Kon Tikito demonstrate migration of
South Americans to Pacific Ocean islands.
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European Navigators
Phoeneciansfirst from Western
Hemisphere to develop navigation arts
Navigated circa 2000 B.C.
Explored Mediterranean Sea, Red Sea, and
Indian Ocean
First circumnavigation of Africa
Reached the British Isles
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European Navigators
Greek Pytheas
Sailed northward using a simple method to
determine latitude in 325 B.C.
Navigated using the North Star
Eratosthenesdetermined Earths
circumference fairly accurately.
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Europeans
Herodotusproducedinaccurate world maparound 450 B.C.
Claudius Ptolomy
produced fairlyaccurate world maparound 150A.D. Erroneously updated
Eratosthenes originalcircumferenceestimation, later causingChristopher Columbusto believe he hadreached Asia
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The Middle Ages
Arabsdominant navigators in the
Mediterranean Sea
Traded extensively with East Africa, India,
and Southeast Asia
Learned to use Indian Ocean monsoon
winds for travel
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Viking Routes and Colonies
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The Age of Discovery in Europe
14921522
Spaniard Ferdinand Magellan
circumnavigated the globe.
Was killed on a Pacific Island in 1521
Juan Sebastian del Cao completed thecircumnavigation in 1522.
Voyages paved the way for the Spanish to
take gold from the Incas and Mayas. Spains maritime dominance ended when
England defeated the Spanish Armada in
1588.
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Voyages of Columbus and
Magellan
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Voyaging for Science
The English wanted to retain maritimesuperiority.
Captain James Cook (17281779)
undertook three scientific voyages. Ships HMSEndeavour, Resolution,
Adventure
Mapped many islands in Pacific
Systematically measured oceancharacteristics
Marine chronograph (longitude)
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Cooks Voyages
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Oceanography Continues
More high-technology tools available today
Sonar
Robotics
Computers
Satellites
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Nature of Scientific Inquiry
Natural phenomena governed by physical
processes
Physical processes similar today as in the
past
Scientists discover these processes and
make predictions
Called the scientific method
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The Scientific Method
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Theories and Truth
Science never reaches absolute truth.
Truth isprobableand based on available
observations.
New observations yield scientific progress.
In reality, scientists have no formal
method.
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Formation of Earth and the Solar
System
Nebularhypothesisallbodies in the solar
system formedfrom nebula
Nebula = cloud ofgases and space
dust Mainly
hydrogen and
helium
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Nebular Hypothesis Gravity concentrates material at center
of cloud (Sun)
Protoplanets form from smallerconcentrations of matter (eddies)
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Protoearth
Larger than Earthtoday
Homogeneous
composition Bombarded bymeteorites
Moon formed
from collisionwith largeasteroid
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Protoearth
Radioactive heatSpontaneous disintegration of atoms
Fusion reactions
Heat from contraction (protoplanet
shrinks due to gravity)
Protoearth partially melts Density stratification (layered Earth)
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Density Stratification
High density = heavy for its size
Early Earth experienced gravitational
separation.
High density materials (Iron and Nickel)
settled in core.
Less dense materials formed concentric
spheres around core.
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Earths Internal Structure
Layers defined by
Chemical composition
Physical properties
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Layers by Chemical
Composition Crust
Low-density, mainly silicate minerals
Mantle
Mainly iron (Fe) and magnesium (Mg)silicate minerals
Core
High-density, mainly iron (Fe) andnickel (Ni)
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Layers by Physical Properties
Lithosphere
Asthenosphere
Mesosphere Outer core
Inner core
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Lithosphere
Cool, rigid shell
Includes crust and
upper mantle
About 100 km(60 miles) thick
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Continental vs. Oceanic Crust
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Asthenosphere
Relatively hot, plastic
Flows with high viscosity
Important for movement of lithospheric plates
Base of lithosphere to about 700 km
(430 miles) deep
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Isostatic Adjustment
Vertical movement of Earths crust
Buoyancy of lithosphere on asthenosphere
Less dense continental crust floats higher
than denser oceanic crust
Isostatic reboundrising of crust formerly
weighed down by glacier ice
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Isostatic Adjustment
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Origin of Earths Atmosphere
Outgassingoccurred during density
stratification
Water vapor
Carbon dioxide
Hydrogen
Other gases
Earths early atmosphere different from today
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Development of Earths Oceans
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Lifes Possible Ocean Origins
Earths earliest known life forms are
3.5-billion-year-old bacteria fossilized in
ocean rocks.
These are the building blocks for life on
early Earth.
There is no direct evidence of early Earths
environment.
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Oxygen
Humans require O2.
Ozone (O3) protects from ultraviolet radiation.
Early Earth had little free oxygen.
The lack of ozone may have helped
originate life.
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Stanley Millers Experiment
Organic molecules formed by ultraviolet
light, electrical spark (lightning), and a
mixture of water, carbon dioxide,
hydrogen, methane, and ammonia
St l Mill d hi
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Stanley Miller and his
Experiment
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Evolution and Natural Selection
Organisms adapt and change through time.
Advantageous traits are naturally selected.
Traits are passed to the next generation.
Organisms adapt to environments.
Organisms can modify environments.
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Plants and Animals Evolve
Heterotrophs
Very earliest life
Require external food supply
Autotrophs
Evolved later
Manufacture own food supply
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First Autotrophs
Probably similar to modern anaerobic
bacteria
Survive without oxygen
Chemosynthesisfrom chemicals at deep
hydrothermal vents
Supports idea of lifes origins on deep
ocean floor in absence of light
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Photosynthesis and Respiration
Complex autotrophs developed chlorophyll.
This allowed the use of the Sun for
photosynthesis.
Cellular respiration
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Photosynthesis and Respiration
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Great Oxidation Event
2.45 billion years ago
Increased oxygen and ozone eliminated
the anaerobe food supply.
Light and oxygen kill anaerobes.
Cyanobacteria adapted and thrived.
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Changes to Earths Atmosphere
Photosyntheticorganisms areresponsible for life aswe know it today.
Reduce CO2,increase O2to 21%
High oxygen =biodiversity increase
Low oxygenassociated withextinction events
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Plants and Earths Environment
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Age of Earth
Radiometric age dating
Spontaneous change/decay
Half-life Earth is about 4.6 billion years old.
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Radioactive Decay
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End of CHAPTER 1
Introduction to Planet Earth