Transcript Earth Science Introduction

Introduction to Earth Science
Or, How The Earth Works
Branches of Earth Science
• Geology
– Solid Earth Much Larger than Other Parts
– Many More Kinds of Materials
– Preserves a History
• Meteorology – Climatology
• Oceanography
• Astronomy
– Planetary Geology
The Earth Systems
•
•
•
•
•
•
External Effects (Astronomical)
Atmospheric Circulation
Oceanic Circulation
Hydrologic Cycle
Rock Cycle
Plate Tectonics
The Solid Earth
Earth and the Universe
(external effects)
•
•
•
•
•
•
Earths’ Rotation (Day-Night)
Lunar Effects (Tides)
Annual Variation (Seasons)
Precession and Orbit Variations (Ice Ages?)
Galactic Rotation (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
• Heating and Cooling
• Coriolis Effect
• High and Low Air Pressures
• Fronts and Air Masses
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
and
Resources
Configuration of Continents
• Oceanic Circulation
• Weather and Climate Patterns
– Deserts
– Mountains and Rain Shadows
• Pathways for Migration
• Ecological Niches
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
• 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 (Keep It Simple)
• 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:
Road Cut,
Superior, AZ
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