Chapter 1 Objectives

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Chapter 1 Objectives

• This is the introductory chapter. After reading
  this chapter you should be able to
• 1. Identify the four spheres of Earth
• 2. Describe the composition of each sphere.
• 3. List forms of interaction between spheres.
• 4. Define a system
• 5. Describe the types and rates of changes.
• 6. Describe the scientific method.
• 7. Explain the importance of geologic time.

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Our Solar System

• Our Solar System evolved about 4.6 billion years
  ago from a cloud of dust and gas that rotated in
  space and eventually coalesced into the Sun, the
  planets and their moons under the pull of
  gravity. Yet today, all of the planets are
  different. Lets compare Venus, Mars and Earth.

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Venus

• Is it hospitable? It most resembles Earth
  in size, density and distance from the Sun, but
  atmosphere is rich in carbon dioxide and caustic
  sulfuric clouds fill the sky. Lead would melt at
  the surfacewhy so different then Earth?

Fig. 1-1, p.3
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Mars

• Evidence of water. Its surface has similar
  features as Earth (water features such as extinct
  canyons, stream channels, lake beds). At one
  time this planet may have had flowing water but
  today, it is frigid and dry with ice caps of
  frozen carbon dioxide.

Fig. 1-2, p.3
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• If these planets formed at the same time, why
  are they so different today? The original
  atmospheres of Earth, Venus and Mars evolved into
  swirling mixtures of carbon dioxide and carbon
  monoxide, water, ammonia, methane and other
  gases. Consider how H2O and CO2 exist on Earth.
• Venus closer to the Sun, water never condensed,
  CO2 remained in the atmosphere (no seas to
  dissolve in). These greenhouse gases (H20, CO2)
  would have what effect?
• Earth cool enough for water vapor to condense,
  form oceans and dissolve CO2 from the
  atmosphereso large quantities of greenhouse
  gases removed from the atmosphere and it cooled
  at a temperature favorable for liquid water and
  life. Our initial atmosphere replaced by an
  atmosphere rich in nitrogen and oxygen. Where
  did the oxygen come from?
• Mars a little farther from the Sun than Earth,
  less solar radiation. Initially rain fell,
  rivers flowed, and lakes/oceans formed (possibly
  life formed). But distance from Sun lowered
  greenhouse gases in atmosphere. Temperatures
  dropped (commonly below freezing to as low as
  -140 degrees C or -220 degrees F).

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The Earths four spheres

• Planetary changes are driven by complex
  interactions among the spheres
• On Earth, what are they?
• Which one is largest? (see page 5).

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1.2 The Earths four spheres

• Geosphere - the solid earth
• Planets accreted from dust into planetesimals
• Planetesimals clumped together to form planets
• Colliding pieces (and radioactivity) created
  heat, warming the young Earth to melting and
  differentiation into layers
• This ended (or Earth started) about 4.6 billion
  years ago

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The Earths Layers Core, Mantle and Crust

• Metallic core Fe and Ni, temp hot as Suns
  surface (6000 degrees C), inner core is solid,
  outer core is liquid.
• Less-dense rocky mantle Changes with depth, some
  parts solid, others weak and plastic-like,
  flowing slowly.
• Least-dense crust crustal material varies widely.

Fig. 1-4, p.6
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Granitic Rock of Baffin Island, Canada(common
rock of the continental crust formed from magma)
Fig. 1-5a, p.6
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Sandstone and Limestone of the desert in Utah,
USA(how do these types of rock form?)
Fig. 1-5b, p.6
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• Lithosphere the crust and upper part of mantle
• Average 100km thick
• Broken up into tectonic plates
• Plates float atop the weaker material
• 7 major (and several minor) plates are in
  constant motion

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The Earths Interior

• A slice through the Earth. According to Plate
  Tectonics Theory, the lithosphere is broken into
  segments called tectonic plates. They move on
  the asthenosphere at about the rate your
  fingernail grows. This movement accounts for
  earthquakes, volcanoes, other phenomena.

Fig. 1-6, p.7
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• Hydrosphere
• All of Earths water
• Oceans not only contain 97.5 of Earths water,
  but cover 71 of the Earths surface.
• Glaciers cover 10 of the Earths surface and
  contain about 1.8 of its water.
• Only 0.01 is water at Earths surface (streams,
  lakes), 0.63 is underground and 0.001 is in the
  atmosphere

Fig. 1-7, p.7
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• Atmosphere
• Mixture of gases, mostly nitrogen and oxygen.
• Held by what force?
• Mostly concentrated (99) in the first 30 km
  above Earth.
• Supports life, acts as a filter (shield) and
  blanket. Transport heat around the globe.

Fig. 1-8, p.8
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Biosphere

• Zone inhabited by life.
• Includes the uppermost geosphere, hydrosphere and
  lower atmosphere.
• Plants and animals not only depend on the Earths
  environment, but alter and form the environment
  they live in.

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Earth Systems

• System assemblage or combination of interacting
  components that form a complex whole.
• Systems are driven by flow of energy and matter.
  Large systems are composed of many smaller
  onesthe human body for exampleand humans
  interact in ecosystems, which interact with other
  Earth systems!
• Earths major systems are its spheres, subdivided
  into many interacting smaller ones. Discuss a
  volcanic eruption?
• What are Earths systems powered by??
  
• Several energy and material cycles are important
  in our study of Earths systemswhat is one of
  these? All spheres continuously exchange matter
  and energy. Earths materials and processes are
  part of one integrated system

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• The Carbon Cycle All of Earths cycles and
  spheres are interconnected. For example, the
  formation and decomposition of limestone is part
  of the rock cycle because limestone is a rock.
  The same process is also part of the carbon cycle
  because limestone is composed partly of carbon.

Fig. 1-9, p.10
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• Earths cycles and spheres are interconnected.

Fig. 1-10, p.11
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Time and Earth Science

• James Hutton, 1700s. Regarded by many as the
  Father of Geology. Observed how sandstone
  formed, deduced the Earth must be very old.
• He formulated uniformitarianism (gradualism)
  geologic change occurs over long periods of time,
  by a sequence of almost imperceptible events
  (erosion, plate motions).
• The present is the key to the past (explain
  geologic events of the past by observing changes
  today).
• Not all change is gradual Catastrophism
  occurs, this idea was put forth by geologist
  William Whewell (floods, earthquakes).

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• Hutton observed that a sandstone outcrop, like
  this one in Utah, is composed of tiny round sand
  grains cemented together.

Fig. 1-11, p.12
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• Today we know from age dating rocks and other
  methods that the Earth is about 4.6 billion years
  old.

Fig. 1-12, p.13
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• -Most geologic change is gradual. Movement of
  tectonic plates is slow, yet accounts for
  mountains, volcanic eruptions, earthquakes and
  other geologic phenomena.
• -Catastrophic events have occurred throughout
  the 4.6 billion years of Earths history. 50,000
  years ago, a meteorite crashed into the Arizona
  desert, creating meteor crater. Larger impacts
  may have caused mass extinctions (possibly
  killing the dinosaurs off 65 million years ago).

Fig. 1-13, p.14
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1.5 Threshold and feedback effects

• Threshold effect slow or no initial change to
  environmental change
• When threshold point is passed, change becomes
  rapid (for example, melting of glaciers).
• Feedback mechanism
• one change affects another system component,
  amplifying original effectcan be positive or
  negative.

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• Today there are approx. 6.5 billion people on
  Earth.
• 40 of land area is developed.
• Species extinction rate is high.
• CO2 is at a high level (Earths temp raised .6
  degree C since Industrial revolution).
• Do we have enough resources?
• Will our growth trigger climate changes?

Fig. 1-14, p.15
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• Current trends
• Population is increasing, but slower (7-14
  billion estimated when stable)
• India/China becoming richer richer people
  consume more resources
• Population and consumption continue to rise with
  serious environmental consequence (see Table 1.1)

Fig. 1-16, p.18
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Carrying Capacity

• How many people can Earth support?
• Calculations of carrying capacity vary
  considerably
• Increasing amounts of food can be produced
• People can migrate from areas of famine or
  poverty to less crowded or wealthier areas

• BUT Earths resources are finite, so solutions
  are temporary

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Carrying Capacity

• Example of Rapa Nui (Easter Island)
• Isolated Pacific island with poor soil and little
  water
• Settled by 25-50 Polynesians in 5th century

• Survived easily on chickens and yams, plenty of
  free time
• Developed elaborate competition between clans
  with moai (statues)
• Civilization peaked at 1550, with population of
  7000

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Carrying Capacity

• Example of Rapa Nui (Easter Island)
• Reached by a Dutch ship in 1722
• Found about 2,000 people living in caves
• Primitive society, constant warfare
• Rapa Nuis carrying capacity had been drastically
  lowered by societys actions
• Transportation of moai had required cutting down
  trees
• Erosion of soil made yams scarce
• Lack of canoes made fishing difficult and escape
  impossible

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The Scientific Method (see page 15)

• Observation, Hypothesis, Theory and Law.
• Observation starting point of science. Collect
  facts.
• Hypothesis tentative explanation built on strong
  supporting evidence. Tested by comparison,
  additional observations and experiments.
• Theory If hypothesis explains new observations
  and is not substantively contradicted, can become
  a theory. Should be supported and explain many
  observations without major inconsistencies
  (theory of plate tectonics).
• Law statement of how events always occur under
  given conditions. Considered factual and correct
  (law of gravity). Very few laws.

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Fig. 1-15, p.16