How The Earth Works
The Solid Earth
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
Atmospheric Circulation
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
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
Convection
Convection In The Earth
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