Intro to Physical Geology (EAR 110)

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Intro to Physical Geology (EAR 110)
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What is Geology? the study of Earth

• Two Divisions
• Physical geology ? minerals, rocks, Earth
  processes
• Historical geology ? origin evolution of
  continents, oceans, atmosphere, life

interdisciplinary (astronomy, biology, physics,
chemistry)
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Why is Geology Important to You?

• Minerals have practical daily uses.
  
• (toothpaste, vitamins, drink cans, cosmetics,
  salt, pencil lead, jewelry, currency, ceramics,
  paints, fertilizers, lubricants, abrasives, etc.)

• Informed decisions are essential.
• (i.e., mineral rights, safety of water supply,
• stream flooding, community planning boards,
• communication to legislators enacting
• environmental regulations)

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• Knowledge of geologic hazards lessens the
  severity of their impact.

• Standard of living is dependent on the use of
  geologic materials. (i.e., Overuse of resources
  adversely affects balance of nature, culture,
  environment.)

Sustainable development insures future
generations sufficient natural resources to
maintain standard of living for a larger
population.
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A complex, dynamic system

• SYSTEMS atmosphere, biosphere, hydrosphere,
  lithosphere, mantle, core.

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3 Physical Environments

• 1. Solid Earth core, mantle, crust
• 2. Hydrosphere dynamic mass of H2O
• The Water Cycle
• --evaporation from oceans into the atmosphere
• -- precipitation onto land
• -- water flows back into the oceans
• 3. Atmosphere gaseous envelope around Earth 
• (interaction b/w surface atm. ? WEATHER)

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Characteristics of Earths Core

• composed of Fe (minor Ni other heavy elements)
• inner core solid, Fe-rich sphere
• outer core molten metallic layer
• Theyre compositionally similar.
• Magnetic field ? provided by circulation of the
  molten outer core

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Characteristics of Earths Mantle

• 82 of Earth ? 2900km thick
• located below the crust
• behaves like a solid when EQs pass thru it, but
  can flow slowly (plastic)
• Divided into regions
• Upper (Asthenosphere)
  crust thru upper mantle (660km
  into Earth)
• Lower (Mesosphere)
  from a depth of 660km to the
  outer core

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Characteristics of Earths Crust

• LITHOSPHERE ? rigid, solid
• Thickness Average 15 km
• 3 km (2mi) at ocean ridges
• 70 km (40 mi) in ancient mtn belts
• Oceanic Continental
• Basalt/Gabbro Andesite/Granodiori
  te
• more dense (3 g/cm3) less dense
  (2.7 g/cm3)
• younger (180 my to pres) older (up to
  3.8 by)

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Formulation of Theories

• theory ? speculative explanation wild guess
• theory (scientific) ? coherent explanation
  supported by large body of evidence validity of
  explanation testable by experiment
• How are theories born?
• The Scientific Method
• Refinement occurs by further testing.

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The Scientific Method

• 1.   Collection of Data
• ? gather scientific facts thru
  observations measurements
• 2.   Hypothesis formation
• ? theory vs. hypothesis?
• 3.   Tests of the hypothesis
• ? develop experiments for testing
• 4.   Acceptance, modification, or rejection of
  the hypothesis

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Plate Tectonic Theory

• Lithosphere is divided into plates that fit like
  jigsaw puzzle pieces across Earths surface.

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Plate Tectonics Theory

• Continental drift ? Continents moved across
  Earths surface. (50 yrs for acceptance)
• Plates float on asthenosphere as they move they
  interact along their boundaries.
• Plate movement is driven by the unequal
  distribution of heat w/in Earth.
• 1) major landscape features (mtns, valleys)
• 2) distributes natl. resources
• 3) distribution evolution of the biosphere

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Types of Plate Boundaries
CONVERGENT (subduction zones) dense plates
subduct under less dense plates subducted plate
goes into the mantle melts
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• DIVERGENT (mid-ocean ridges)
• seafloor spreading ? fractures open, molten
  mat. from asthenosphere fills fractures

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TRANSFORM FAULT
plates move horizontally
past one another w/out consuming old lithosphere
or generating new lithosphere
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The Rock Cycle

• relates the formation of the major rock groups
  to internal external processes

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Uniformitarianism late 1700s   James Hutton
Scottish physician very intelligent not able
to convey his thoughts   The present is the key
to the past.   Laws that govern the physical,
chemical, and biological processes occurring now
on the earth, also operated in the past...
(i.e., These processes are unchanging through
time.)     Charles Lyell Principles of Geology
(mid 1800s)   noted that processes may have
been operating at varying rates in the past or
that they may not have had the same significance
as they do today
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Above Mudcracks

• Lower Right Bird tracks

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• Geologic Time Scale
• 19th century geologists arranged info from
  outcrops based on changes in biota thru time
  (relative age).
• Radiometric dating (20th century)
  assigned absolute age dates to the
  sub-divisions.