Geology is the study of Earth in all of its physical, chemical and biological dimensions

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geology
Geology is the study of Earth in all of its
physical, chemical and biological dimensions
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Protosun fuses hydrogen, becomes the Sun, solar
pressure clears away planet-building materials
Current solar system
Accretion of planetesimals
Protoplanetary disk rotates faster, flattens, and
protosun develops
Solar nebula collapses and rotates
Fig. 1-9, p. 13
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Learning Objectives

• Explain how the Earth systems or spheres
  interact.
• Explain the Earths internal and external energy
  sources
• Identify the the Earths composition (surface and
  interior)
• Identify the eons, eras, periods, and epochs on
  the geologic time scale.
• Relate geologic time to the evolution of the
  Earth.

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THE EARTH Systems or Spheres

• The Earth is a dynamic, ever-changing planet.
• Earth is a complex, integrated system.
• The Earth has four spheres that are subsystems of
  the larger Earth system.
• Each sphere is connected to the other by
  processes or cycles.
• The internal and external energy sources of the
  Earth are the driving mechanism for change.

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Fig. 1-2, p. 4
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Fig. 1-3, p. 5
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The Different Spheres

• Atmosphere (atmos means ____)
• Hydrosphere (hydro means ____)
• Biosphere (bio means ____)
• Lithosphere (litho means ____)
• Using Figure 1-3, explain the interactions
  between the different spheres. Using examples,
  explain four different interactions between any
  of the four spheres.

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Table 1-1, p. 5
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Earth and Energy

• Energy is required for the Earths spheres to
  interact.
• External Energy Source
• The Sun
• Internal Sources
• Heat leftover from formation
• Heat from gravitational contraction
• Heat from extraterrestrial impacts
• Decay of radioactive elements
• Friction from the movement of the plates and
  convection in the mantle

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Decay of Radioactive Elements

• http//serc.carleton.edu/NAGTWorkshops/visualizati
  on/collections/RadioDec.html
• Unstable element such as Uranium 238 decays to
  Lead 206
• Earth has cooled over time as radioactive
  elements decay to stable elements.

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Differentiation
More dense material sinks (molten iron and
nickel) leaving the less dense material
(silicates) near the surface
Gases emitted from the interior during this
process are likely the source for the formation
of the atmosphere and oceans.
Fig. 1-10, p. 14
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The Earths Layers

• Earth layers result from density differences
  between the layers caused by variations in
  composition, temperature, and pressure.
• Core metal (Fe and small amount of Ni) 10-13
  g/cm3
• Outer liquid core
• Inner solid core
• Mantle iron-rich rock (FeMg-Peridotite) 3.35.7
  g/cm3
• Crust aluminum and magnesium rich rock
• Continental Crust SiAl (rock) less dense 2.7
  g/cm3
• Oceanic Crust SiMa (rock) more dense 3.0 g/cm3

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Components of the Earths Crust

• Elements (Si and O are most abundant, traces of
  radioactive elements)
• Minerals (naturally occurring, inorganic
  crystalline solids, gemstones, metals)
• Rocks (igneous, sedimentary and metamorphic)
  Rocks are composed of minerals.
• Natural resources/fossil fuels (coal, natural gas
  and oil)
• Soils (weathered rock, air, water and organic
  material)

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Lithosphere and Asthenosphere

• Lithosphere is the solid, brittle outer layer of
  the Earth composed of
• Oceanic and continental crust
• Top part of the mantle
• Asthenosphere is the plastic layer of the mantle
  directly below the lithosphere over which the
  lithospheric plates move.
• The lithosphere is broken into many pieces called
  plates.

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Fig. 1-11, p. 15
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Geologic Time

• Earth is 4.6 billion years old (as old as the
  formation of the solar system)
• To a geologist, recent geologic events are those
  that occurred within the last million years.
• The Earth goes through cycles that are much
  longer in duration than our human perspective of
  time.

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Assessing the Age of the Earth

• Geologists placed relative dates on exposed rock
  formations based on
• similarities and differences in rock composition
  and the preserved biota.
• relative positions of these rock formations
• Geologists later placed an absolute dates on rock
  using radiometric dating techniques to confirm
  relative ages.

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Geologic Time Scale
Ages in millions of years
Todays Geologic Date Recent Epoch Quaternary
Period Cenozoic Era Phanerozoic Eon
The Earth is currently experiencing an
interglacial episode
Fig. 17-1, p. 394
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CHAPTER SUMMARY

• We can view Earth as a system of interconnected
  components that interact and affect one another.
  The principal subsystems of Earth are the
  atmosphere, hydrosphere, biosphere, lithosphere,
  mantle, and core. Earth is considered a dynamic
  planet that is continuously changing because of
  the interactions among its various subsystems and
  cycles.
• Geology, the study of Earth, is divided into two
  broad areas Physical geology is the study of
  Earth materials as well as the processes that
  operate within and on Earths surface historical
  geology examines the origin and evolution of
  Earth, its continents, oceans, atmosphere, and
  life.
• Geology is part of the human experience. We can
  find references to it in the arts, music, and
  literature. A basic understanding of geology is
  also important for dealing with the many
  environmental problems and issues facing society.
• Geologists engage in a variety of occupations,
  the main one being exploration for mineral and
  energy resources. They are also becoming
  increasingly involved in environmental issues and
  making shortand long-range predictions of the
  potential dangers from such natural disasters as
  volcanic eruptions and earthquakes.

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CHAPTER SUMMARY

• About 4.6 billion years ago, the solar system
  formed from a rotating cloud of interstellar
  matter. Eventually, as this cloud condensed, it
  collapsed under the influence of gravity and
  flattened into a rotating disk. Within this
  rotating disk, the Sun, planets, and moons formed
  from the turbulent eddies of nebular gases and
  solids.
• Earth is differentiated into layers. The
  outermost layer is the crust, which is divided
  into continental and oceanic portions. Below the
  crust is the solid portion of the upper mantle.
  The crust and solid part of the upper mantle, or
  lithosphere, overlie the asthenosphere, a zone
  that slowly flows. The asthenosphere is underlain
  by the solid lower mantle. Earths core consists
  of an outer liquid portion and an inner solid
  portion.
• The scientific method is an orderly, logical
  approach that involves gathering and analyzing
  facts about a particular phenomenon, formulating
  hypotheses to explain the phenomenon, testing the
  hypotheses, and finally proposing a theory. A
  theory is a testable explanation for some natural
  phenomenon that has a large body of supporting
  evidence.
• The lithosphere is broken into a series of plates
  that diverge, converge, and slide sideways past
  one another.

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CHAPTER SUMMARY

• Plate tectonic theory provides a unifying
  explanation for many geologic features and
  events. The interaction between plates is
  responsible for volcanic eruptions, earthquakes,
  the formation of mountain ranges and ocean
  basins, and the recycling of rock material.
• The rock cycle illustrates the interactions among
  internal and external Earth processes and shows
  how the three rock groups are interrelated.
• Igneous, sedimentary, and metamorphic rocks are
  the three major groups of rocks. Igneous rocks
  result from the crystallization of magma or the
  consolidation of volcanic ejecta. Sedimentary
  rocks are formed mostly by the consolidation of
  rock fragments, precipitation of mineral matter
  from solution, or compaction of plant or animal
  remains. Metamorphic rocks are produced from
  other rocks, generally beneath Earths surface,
  by heat, pressure, and chemically active fluids.
• Time sets geology apart from the other sciences,
  except astronomy, and an appreciation of the
  immensity of geologic time is central to
  understanding Earths evolution. The geologic
  time scale is the calendar geologists use to date
  past events.
• The principle of uniformitarianism is basic to
  the interpretation of Earth history. This
  principle holds that the laws of nature have been
  constant through time and that the same processes
  that operate today have operated throughout the
  past, though at different rates.