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How The Earth Works
The Solid Earth
Earth Science
• Geology
– Solid Earth Much Larger than Other Parts
– Many More Kinds of Materials
– Preserves a History
• Meteorology – Climatology
• Oceanography
• Astronomy
– Planetary Geology
Earth Systems
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External Effects (Astronomical)
Atmospheric Circulation
Oceanic Circulation
Hydrologic Cycle
Rock Cycle
Plate Tectonics
Earth Systems
Earth Systems
Earth Systems
Earth Systems
Earth Systems
Earth Systems
Earth Systems
Earth Systems
Convection
Earth and the Universe
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Rotation (Day-Night)
Lunar (Tides)
Annual (Seasons)
Precession and Orbit Variations (Ice Ages?)
Galactic (250 m.y. period)
Unpredictable Events
– Nearby Supernovae
– Meteor Impacts
• Long-Term Evolution of Sun
Atmospheric Circulation
• Unequal Solar Heating
– Equator to Pole
– Day - Night
– Different Surfaces
• Buoyancy
• Adiabatic Heating and Cooling
• Coriolis Effect
• High and Low Pressure
• Fronts and Air Masses
Rotation Effects
Rotation Effects
Rotation Effects
The Coriolis Effect
• Due to moving on a
rotating earth
• Things on equator are
moving faster than
points near poles
• Affects:
– Winds
– Ocean Currents
– Tides
The Coriolis Effect
• Things moving
toward the equator are
deflected west
• Things moving
poleward are
deflected east
• Counterclockwise in
Northern Hemisphere
• Clockwise in
Southern Hemisphere
Not a
Manifestation of
the Coriolis
Effect!
• Too small scale
for the Coriolis
Effect to be
significant
Atmospheric Circulation
1905 Weather Map
Oceanic Circulation
• Surface Currents - Driven by Winds
• Thermohaline - Deep Circulation
– Evaporation makes water more saline and
denser
– Freezing makes water more saline and denser
– Cold water is denser than warm water
Early Map of Gulf Stream
Surface Currents
Thermohaline Circulation
Hydrologic Cycle
• Evaporation from Oceans
• Precipitation on Land
– Infiltration into Ground (Ground Water)
– Runoff (Erosion)
Hydrologic Cycle
Water
• Principal Agent in Modifying Earth’s
Surface
• Medium for Storing and Distributing Global
Heat
• The Universal Solvent
– Essential for Life
– Destructive to Rocks
• Lowers Melting Point of Rocks
• Reduces Strength of Rocks Under Pressure
The Rock Cycle
• New Rocks Exposed by Erosion
• Rocks Broken Down Mechanically and
Chemically (Weathering)
• Components Transported by Erosion
• Components Cemented into Sedimentary Rocks
• Burial and Heating creates Metamorphic Rocks
• Melting Creates Igneous Rocks
The Rock Cycle
Plate Tectonics
• Outer Crust of Earth Moves a Few cm/yr
• Driven by Convection in Earth’s Interior
• Accounts For:
– Earthquakes
– Volcanoes
– Mountain-Building (Orogeny)
• Configuration of Continents
Plate Tectonics
Plate
Tectonics
and
Resources
Configuration of Continents
• Oceanic Circulation
• Weather and Climate Patterns
– Deserts
– Mountains and Rain Shadows
• Pathways for Migration
• Ecological Niches
Configuration of Continents
Some Unique Aspects of
Geology
Importance of Relationships
• Sequential
• Spatial
Importance of Time
Distinctive Problems of Evidence
• Slow Rates
• Rare Events
• Destruction of Evidence
• Inaccessibility
Some Geologic Rates
Cutting of Grand Canyon
• 2 km/3 m.y. = 1 cm/15 yr
Uplift of Alps
• 5 km/10 m.y. = 1 cm/20 yr.
Opening of Atlantic
• 5000 km/180 m.y. = 2.8 cm/yr.
Uplift of White Mtns. (N.H.) Granites
• 8 km/150 m.y. = 1 cm/190 yr.
Some Geologic Rates
Movement of San Andreas Fault
• 5 cm/yr = 7 m/140 yr.
Growth of Mt. St. Helens
• 3 km/30,000 yr = 10 cm/yr.
Deposition of Niagara Dolomite
• 100 m/ 1 m.y.? = 1 cm/100 yr.
1 Second = 1 Year
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35 minutes to birth of Christ
1 hour+ to pyramids
3 hours to retreat of glaciers from Wisconsin
12 days = 1 million years
2 years to extinction of dinosaurs
14 years to age of Niagara Escarpment
31 years = 1 billion years
Some Unique Aspects of
Geology (Continued)
Reliance on Inference and Deduction
Intrinsically "Unsolvable" Problems
• Ancient Landscapes
• Mass Extinctions
• Ancient Ocean Basins
Scientific Principles in Geology
• Parsimony (K.I.S.S.)
• Superposition
• Uniformitarianism
Using these, plus observation, we establish
facts about Earth Processes
Parsimony
• The simplest explanation that fits all the
data is preferred
• Doesn’t guarantee that things must be
simple!
• Theories with lots of ad hoc or unsupported
ideas are probably wrong.
Superposition:
Mindoro Cut,
Wisconsin
Geologic
Map
Uniformitarianism
Continuity of Cause and Effect
• Apply Cause and Effect to Future Prediction
• Apply Cause and Effect to Present Technology
• Apply Cause and Effect to Past Uniformitarianism