Introduction to Physical Geology

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Lecture 2 Introduction to Physical Geology
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Lecture Outline
Physical Geology
I Geological Paradigms II Origins A) The Solar
System B) The Earth III Fundamental Concepts of
Physical Geology A) Geologic Time B) The
Earth's Structure i. Earth's
Layers ii. Plate Tectonics - From
Continental Drift to Plate Tectonics - Lithosp
heric Plates - Plate Boundaries C) The Rock
Cycle IV Planetary Geology V Conclusions
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Geological Paradigms
Physical Geology
paradigm, n a collection of beliefs shared by
scientists a set of agreements about how
problems are to be understood
James Ussher (1581-1656) catastrophism
James Hutton (1726-1797) uniformitarianism rock
cycle
Charles Lyell (1797-1875) geologic time
Alfred Wegener (1880-1930) continental drift
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Origin of the Solar SystemThe Nebular Hypothesis
Physical Geology
Palomar Observatory
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Origin of the Solar SystemThe Nebular Hypothesis
Physical Geology
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Origin of the Solar SystemThe Nebular Hypothesis
Physical Geology
gravity
physical collision
clumps of dust grains (cm)
Planetesimals (km)
planetesimals (10-100 km)
protoplanet (100-1000km)
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The Solar SystemWhat is a Planet?
Physical Geology
(1) A planet1 is a celestial body that (a) is
in orbit around the Sun, (b) has sufficient mass
for its self-gravity to overcome rigid body
forces so that it assumes a hydrostatic
equilibrium (nearly round) shape, and (c) has
cleared the neighbourhood around its orbit. (2)
A dwarf planet is a celestial body that (a) is
in orbit around the Sun, (b) has sufficient mass
for its self-gravity to overcome rigid body
forces so that it assumes a hydrostatic
equilibrium (nearly round) shape2 , (c) has not
cleared the neighbourhood around its orbit, and
(d) is not a satellite. (3) All other objects3
except satellites orbiting the Sun shall be
referred to collectively as Small Solar-System
Bodies.
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Origin of the EarthGeological Differentiation
Physical Geology

• Earth melted by
• gravitational energy left from formation of
  planet
• meteor bombardment
• radioactive decay

• Gravity concentrated denser materials (Ni Fe)
  in center
• Less dense materials (silicates) forced to outer
  layers
• Crust became stable after 1 billion years

• Compositional Zones
• Crust
• Continental
• Oceanic
• Mantle
• Core
• Outer (Liquid)
• Inner (Solid)

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Fundamental ConceptsEarth's Layers
Physical Geology

• Compositional Zones
• Core
• Solid inner core
• Liquid outer core
• Radius of 3500 km
• 16.2 of Earth's vol.
• 31.5 of Earth's mass
• Generates Earth's magnetic field
• Mantle
• Thickness 2900 km
• 82.3 of Earth's vol.
• 67.8 of Earth's mass
• Crust
• Oceanic 4-20km thick
• Continental 30-70km thick

• Mechanical Zones
• Core
• Mesosphere
• Lower mantle
• Rigid
• Very Hot
• Capable of gradual flow
• Asthenosphere
• "weak" layer
• Convecting mantle
• Soft and readily flows
• Lithosphere
• Crust and Upper Mantle
• Rigid
• Brittle

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Fundamental ConceptsGeologic Time
Physical Geology

• Phanerozoic Eon -"Eon of Evident Life"
• Paleozoic Era -"Era of Old Life"
• Mesozoic Era -"Era of Middle Life"
• Cenozoic Era -"Era of Modern Life"

Divisions Eon Era Period Epoch Age
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Fundamental ConceptsPlate Tectonics - The
Evidence
Physical Geology
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Fundamental ConceptsPlate Tectonics - The Ocean
Floor
Physical Geology
Mid-Ocean Ridge System
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Fundamental ConceptsPlate Tectonics - The Ocean
Floor
Physical Geology
Mid-Ocean Ridge System

• underwater mountain range
• 80,000 km long
• 1500-2500 km wide
• up to 3000 m above sea floor
• rift valley, 1-2 km deep, runs along axis
• 4000 km wide fracture systems

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Fundamental ConceptsPlate Tectonics - The Ocean
Floor
Physical Geology
magnetic striping
crustal age
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Fundamental ConceptsPlate Tectonics - The Ocean
Floor
Physical Geology
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Fundamental ConceptsPlate Tectonics - The Engine
Physical Geology
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Fundamental ConceptsPlate Tectonics -
Lithospheric Plates
Physical Geology
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Fundamental ConceptsPlate Tectonics Plate
Boundaries
Physical Geology
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Fundamental ConceptsThe Rock Cycle
Physical Geology

• Atmospheric Processes
• Weathering
• Physical Weathering
• Chemical Weathering
• Biological Weathering
• Sediment Transport
• Lithospheric Processes
• Burial
• Compaction and Cementation
• Heat and Pressure
• Stress
• Plate Tectonics
• Exposure

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Planetary Geology
Physical Geology
Venus
Jupiter
Europa
Magellan
Galileo
Io
Mars
Galileo
Viking 1
Voyager 1
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Planetary GeologyMars
Physical Geology
Physical Geology