Earth: Basic Facts• 150 million km from Sun (93 million miles)• Diameter, just under 13,000 km (8,000 mi.)• Density: 5.5 g/cc (5500 kg/m3)
– About twice as dense as surface rocks– Earth has a dense core
• Unique Features– Liquid Surface– Plate Tectonics– Life
Earth Systems• External Effects (Astronomical)• Atmospheric Circulation• Oceanic Circulation• Hydrologic Cycle • Rock Cycle• Plate Tectonics
Earth and the Universe• 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
The Atmosphere• 79% Nitrogen, 20% Oxygen, 1% Argon• Oxygen made by life
– Example: glucose C6H12O6
– 6H2O + 6CO2 C6H12O6 + 6O2
• Greenhouse effect– Infrared absorbed by molecular vibrations– 90% of earth’s greenhouse effect due to water
vapor– Without a greenhouse effect, earth would be
frozen
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
Not a Manifestation of
the Coriolis Effect!
• Too small scale for the Coriolis Effect to be significant
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
Hydrologic Cycle• Evaporation from Oceans• Precipitation on Land
– Infiltration into Ground (Ground Water)– Runoff (Erosion)
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
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
Configuration of Continents
• Oceanic Circulation• Weather and Climate Patterns
– Deserts– Mountains and Rain Shadows
• Pathways for Migration• Ecological Niches
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