How The Earth Works

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

Earth Systems

Earth Systems

Earth Systems

Earth Systems

Earth Systems

Earth Systems

Earth Systems

The Solid Earth

Earth Systems• External Effects (Astronomical)• Atmospheric Circulation• Oceanic Circulation• Hydrologic Cycle • Rock Cycle• Plate Tectonics

Convection

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

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

Convection In The Earth

Convection In The Earth

Plate Tectonics

Plate Tectonics

The Carbonate-Silicate Cycle

Configuration of Continents

• Oceanic Circulation• Weather and Climate Patterns

– Deserts– Mountains and Rain Shadows

• Pathways for Migration• Ecological Niches

Configuration of Continents