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Earth as a Fragile System: Energy Sources (Major Energy Sources (Solar…
Earth as a Fragile System: Energy Sources
Major Energy Sources
Solar Energy
99.9% of energy received by Earth
40% reflected back into atmosphere and oceans
Converted to heat & absorbed by atmosphere, lithosphere, hydrosphere
Absorbed by plants during photosynthesis and stored
Responsible for all natural hazards(severe weather, tornadoes, hurricanes, floods, drought
Gravitational Energy
Force of attraction between two bodies, proportional to masses and inverse to the square of the distance between two bodies
Force of gravity between moon, sun and Earth creates tides
Explains why rocks, soil, mud, and snow can move downhill in landslides or avalanches
Impact Energy
Collisions with meteorites and asteroids, large impacts are rare
Collisions responsible for: shock waves, earthquakes, tsunamis, cooling, mass extinctions
Converted energy of motion to heat
Residual energy still present in internal layers
Internal Energy
Generated in Earth by:
Residual Heat: energy trapped in Earth from impacts that led to Earths formation
Gravitational Energy: energy produced when core and mantle formed, heavy elements moved to centre, lighter to outside
Radioactive Decay: radioactive elements undergo spontaneous degradation. Earth used to have more short lived radioactive elements, therefore produced more heat
0.01% of total energy
Responsible for earthquakes, volcanic eruptions,tsunamis
Earth's Density Layers
Core
Iron rich, densest layer(up to 16g/cm ^3)
Inner Core: Solid, 2450 km diameter
Outer Core: Liquid, magnetic field
Mantle
Surrounds core, 2900 km diameter
Stony
83% of Volume, 67% of mass
Density: 5.7-3.3g/cm^3
Crust
Lies over mantle
Lowest density: average of 2.7 g/cm^3
Forms continents, atmosphere, oceans
Principle of Isostasy: less dense materials float on higher density materials
Mechanical Layers
Mesosphere
Extends from core/mantle boundary to 360 km below Earth's surface
Solid part of mantle, stiff plastic
Asthenosphere
Sits above mesosphere
Fluidlike, plastic rock
Lithosphere
Outer layer of Earth
Rigid, solid rock
Roles of Different Layers
Energy moves from core to surface
Conduction
Atoms vibrate against each other
Moves from high temperature to low temperature
Occurs in solids without the movement of fluid
Convection
Heat moves with material it is contained in
Mantle(asthenosphere) transfers heat to crust
*Conduction is slower than convection
Internal vs. External Hazards
Internally fuelled
Earthquakes
Tsunamis
Volcanoes
Creates new landmasses and landforms(mountains, volcanoes, rifts)Constructive processes
Externally fuelled
Modify and destroy pre-existing landmasses & landforms
Floods
Hurricanes
Erosion