Transcript Powerpoint Presentation Physical Geology, 10th ed.

Lecture Outlines
Physical Geology, 14/e
Plummer, Carlson & Hammersley
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Introducing Geology, the Essentials
of Plate Tectonics, and Other
Important Concepts
Physical Geology 14/e, Chapter 1
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Who Needs Geology?
Geology—the scientific study of Earth
Physical geology
• the study of Earth’s materials,
• changes of the surface and interior of the
Earth,
• and the forces that cause those changes
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Supplying Things we need
Resources We Use
Nonmetals
• ~7100 kg/person/year
Metals
• ~216 kg/person/year
Energy
• 3600 liters petroleum
• 3000 kg coal
• 2300 cubic meters natural gas
• 0.1 kg of uranium
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Protecting the environment
Understanding geology can help us
lessen or prevent damage to the
environment—just as it can be used
to find the resources in the first
place.
Dwindling resources can encourage disregard for ecological
damage caused by extraction activities.
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Avoiding Geologic Hazards
Earthquakes, volcanic eruptions, landslides, floods and tsunamis
are the most dangerous geologic hazards.
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Avoiding Geologic Hazards
Volcanoes—ash flows and
mudflows can overwhelm
populated areas and disrupt air
traffic
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Avoiding Geologic Hazards
Landslides, floods, and wave
erosion
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Earth Systems
Atmosphere—the gases that envelop
the Earth
Hydrosphere—water on or near the
Earth’s surface
Biosphere—all living or once-living
materials
Geosphere—the solid rocky Earth
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An overview of Physical Geology
Earth’s heat engines
External — energy from the Sun
• primary driver of atmospheric and
hydrospheric circulation
• controls weathering of rocks at
Earth’s surface
Internal — heat moving from hot
interior to cooler exterior
• primary driver of most geospheric
phenomena
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Earth’s Interior
Compositional Layers
Crust —very thin outer rocky shell
Mantle—hot solid that flows slowly over
time; Fe-, Mg-, Si-rich minerals
Core
•Outer core - metallic liquid; mostly iron
•Inner core - metallic solid; mostly iron
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Earth’s Interior
Mechanical Layers
Lithosphere
•Rigid/brittle outer shell of Earth
•Composed of both crust and
uppermost mantle
•Makes up Earth’s tectonic plates
Asthenosphere
•Plastic zone on which the
lithosphere floats
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Theory of Plate Tectonics
Continental Drift Hypothesis
• Originally proposed in early 20th century by Alfred Wegener to explain the
“fit of continents”, matching rock types and fossils across ocean basins, etc.
• Insufficient evidence found for driving mechanism; hypothesis initially
rejected
Plate Tectonics Theory
• Originally proposed in the late 1960s
• Included new understanding of the sea- floor
and explanation of driving force
• Describes lithosphere as being broken into
plates that are in motion
• Explains origin and distribution of volcanoes,
fault zones and mountain belts
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Tectonic plate Boundaries
Divergent boundaries
• Plates move apart
• Magma rises, cools and forms
new lithosphere
• Typically expressed as midoceanic ridges
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Tectonic Plate boundaries
Transform boundaries
• Plates slide past one another
• Fault zones, earthquakes mark boundary
• San Andreas fault in California
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Tectonic Plate boundaries
Convergent boundaries
• Plates move toward each other
• Mountain belts and volcanoes
common
• Oceanic plates may sink into
mantle along a subduction zone,
typically marked by a deep
ocean trench
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Surficial Processes
Uplift
• Volcanic and/or tectonic forces build crust up
above sea level
• Removal of material by erosion allows isostatic
uplift of underlying rocks
Weathering and Erosion
• Rainfall and glaciers flow down slopes
• Moving water, ice and wind loosen and erode
geologic materials, creating sediment
Deposition
• Loose sediment is deposited when transport agent
loses its carrying power
• Earlier sediments get buried and harden into
sedimentary rock
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Geologic time
Deep Time
• Most geologic processes occur gradually over millions of years
• Changes typically imperceptible over the span of a human lifetime
• Current best estimate for age of Earth is ~4.55 billion years
Geologic Time and the History of Life
•
•
•
•
544 million years: complex life forms first became abundant
230 million years: reptiles became abundant
65 million years: dinosaurs became extinct
3 million year: humans
Nothing hurries geology
— Mark Twain
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End of Chapter 1
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