Global Change in the Earth System

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Global Change in the Earth System
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Global Change

• One of the most important contributions of
  geology is the verification that the earth
  constantly changes.
• There are many kinds of change.
• Gradual vs. Catastrophic
• Unidirectional vs. Cyclic
• Geogenic vs. Anthropogenic

Van Andel, 1994
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Unidirectional Changes

• Evolution of the Solid Earth
• Evolution of the Atmosphere
• Evolution of the Oceans
• Evolution of Life

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Cyclic Changes

• The Supercontinent (Wilson) Cycle
• The Rock Cycle

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Cyclic Changes

• The Hydrologic Cycle
• The Climate Cycle
• The Sea-Level Cycle
• Biogeochemical Cycles
• Carbon
• Nitrogen
• Sulfur
• Metals
• Trace Elements

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The Carbon Cycle

• Photosynthesis stores energy (sugar and oxygen
  from CO2 and water)
• CO2 H2O ? CH2O O2 (photosynthesis)
• Respiration releases energy (CO2 and water by
  oxidizing organic matter)
• CH2O O2 ? CO2 H2O (cellular respiration)

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The Carbon Cycle and Climate

• Humans are effective at increasing the amount of
  atmospheric CO2.
• Burning fossil fuels
• Acid rain
• Deforestation

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The Carbon Cycle and Climate

• CO2 is a greenhouse gas.
• Greenhouse gases act to warm the atmosphere.
• The greater the amount of greenhouse gases, the
  greater the warming effect.
• Humans add greenhouse gases to the atmosphere at
  rates that exceed removal.

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The Greenhouse Mechanism

• Ultra-violet (UV) radiation from the sun passes
  through the atmosphere. CO2 is transparent to
  UV.
• UV warms the surface of Earth.
• The energy absorbed by the Earths surface is
  re-radiated as Infrared (IR) energy. CO2 is
  opaque to IR.
• Increasing amounts of CO2 enhance this effect.

Ultra-violet
Infrared
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McKenzie, 1998
Ice-core CO2
Atmospheric CO2 measured at Mauna Loa
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Increases in CO2 and use of fossil fuel
Fossil Fuels
CO2
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Global Warming

• Raising global temperatures due to CO2 buildup in
  the atmosphere will have dramatic consequences.
• Shifting vegetation belts
• Melting polar ice
• Global sea-level rise

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Fig. 23.25 a
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Fig. 23.25 b

• W. W. Norton. Adapted from McKenzie, 1998.

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Fig. 23.26 a

• W. W. Norton. Adapted from McKenzie, 1998.

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Fig. 23.26 b

• W. W. Norton. Adapted from McKenzie, 1998.

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Fig. 23.17 b
The Population Bomb

• W. W. Norton

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The Environment vs. Human Society

• Currently, the expanding world population
  requires more resources faces increasing losses
  from natural hazards and contributes to growing
  pollution of the air, water, and land.
• The activities of humans and their consequences
  are now comparable (in both magnitude and in
  rate) to perturbations of the Earth's environment
  from many natural processes.
• Many of these human perturbations are not
  beneficial to life on the planet.

Committee on Status and Research Objectives in
the Solid-Earth Sciences A Critical Assessment
(National Research Council). 1993. Solid-Earth
Sciences Society. National Academy Press.
Washington, DC. 346 p.
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The Environment vs. Human Society

• The rate of change has become so rapid that these
  issues can no longer be ignored if the Earth is
  to be managed as a sustainable habitat.
• To accomplish sustainability will require all of
  our scientific understanding of the natural
  materials and processes, particularly the
  material and energy transfers linking the
  geosphere, hydrosphere, atmosphere, and biosphere.

Committee on Status and Research Objectives in
the Solid-Earth Sciences A Critical Assessment
(National Research Council). 1993. Solid-Earth
Sciences Society. National Academy Press.
Washington, DC. 346 p.
21
The Environment vs. Human Society

• Life prospers or fails at the surface of the
  Earth where these environments intersect.
• Human society faces momentous decisions
  concerning control of many future activities that
  require understanding the Earth.

Committee on Status and Research Objectives in
the Solid-Earth Sciences A Critical Assessment
(National Research Council). 1993. Solid-Earth
Sciences Society. National Academy Press.
Washington, DC. 346 p.