Earth’s “Spheres” - The University of Texas at...
Transcript of Earth’s “Spheres” - The University of Texas at...
1
1
Earth’s “Spheres”
Atmosphere
Hydrosphere
Lithosphere
Biosphere
= The EarthSystem
2
Some Fundamental Principles
The universe is regular, predictable and
quantifiable
Earth’s surface is constantly changing
Everything on Earth operates in cycles
All life forms evolved by natural selection
2
3
Key Factors in Earth’s Evolution
After partial melting, it remains hot insidedue to energy from radioactive elements.
The distance from the Sun and Earth’snatural “greenhouse” allow liquid water to bepresent.
Development of a Biosphere.
4
A Force: Gravity -The Great Leveler
Related to product of masses (m x m) andinversely to distance squared
Weight = mass x g (i.e., weight ≈ mass)
At Earth’s surface, all motion is due togravity
3
5
An Energy - Heat
“Transfer of energy resulting fromtemperature differences”
Bodies at same T are in thermal equilibrium
Sources of heat: internal and external
Internal - radioactive decay; cooling ofinterior
External - sun (also source of light energy)
6
Sources of Interior Heat
Cooling of Earth from its original molten state
Decay of radioactive elements
Major ones are U, Th, K, Rb
One element is converted to another
(Ex. U => Pb)
An energetic particle and heat are released
Same principle as the atomic bomb
4
7
Transfer of Heat
Convection - transfer by flow of fluid ormolten material
Conduction - transfer through a solid
Radiation - transfer through air, liquid orvacuum
8
5
9
Most objects expand when heated
Decreases density (less mass per unit volume)
Density changes cause fluids to move
Less dense rises; denser sinks
Hot air rises; cold air sinks
Heat also causes phase changes (water to vapor)
Salt content also affects density
Heat and Density
10
Gravity and Density
All movements via density changes areaffected by gravity
Objects becoming cooler (i.e., denser) thantheir surroundings will sink
Objects becoming warmer (i.e., less dense)than surroundings will rise
Phase changes are density changes andare affected by gravity
7
13
Natural Energy Sources
Earth's Interior
Sun
HEAT
HEAT AND LIGHT
Biol.Prod.
CurrentsWavesWind
Evap.
ExternalEnergy
InternalEnergy
Buildsmountains
Destroysmountains
Fusion Energy
Fission Energy
14
How did Earth become density stratified?
• Young Earth was probably homogeneous
• Heat and gravitational pressure caused Earth to partiallymelt
• Gravity then pulled iron and other heavy elements into thecenter of Earth, heating the planet further
• Lighter minerals migrated to Earth’s surface and formedthe crust
Earth’s Layers
8
15
Density stratificationresults in an inner andouter core, a mantleand crust.
The Formation Of Earth
16
• Earth’s lost its first atmosphere
• Gases, including water vapor, released by the process ofoutgassing, replaced the first atmosphere.
• Water vapor in the atmosphere condensed into clouds.
• After millions of years, the clouds cooled enough for waterdroplets to form.
• Hot rain fell and boiled back into the clouds.
• Eventually, the surface cooled enough for water to collectin basins.
Where did Water Come From?
9
17The early atmosphere was very different from the atmosphere today.
The Early Atmosphere
18
How old is the Earth, and how do weknow it?
Rocks can be dated by measuring the rateof radioactive decay of certain elements.
The oldest objects found on Earth aremeteorites that are about 4.6 b.y.
Lunar rocks are also this age.