The Cycling of Energy

1
The Cycling of Energy

• Key Concept Various Heat-exchange systems work
  in the Earths system and affect phenomena on
  Earths surface.

2
What You Will Learn

• Heat flow is the transfer of energy from a warmer
  object to a cooler object.
• Energy from the sun, the major source of energy
  for phenomena on Earths surface, is transmitted
  to Earth by radiation.
• Heat from Earths interior reaches the surface
  mostly by convection.

3
The Flow of Energy

• Energy can be carried from one place to another
  by heat flow, waves, or by moving objects.
• Heat flow is the transfer of energy from a warmer
  object to a cooler object.
• Wavessuch as water wave, light waves, and sound
  wavestransfer energy through vibrations.

4

• Waves move energy, but they do not move matter.
• Objects carry energy while they are moving.
• As they move, the objects pass energy to objects
  that they touch.

5

• The sun is the major source of energy for the
  Earth system.
• Heat from Earths interior supplies a much
  smaller amount of energy.
• Energy moves through the processes of radiation,
  convection, and conduction.

6
Radiation

• All energy from the sun travels to Earth in waves
  called electromagnetic radiation.
• Electromagnetic radiation contains a wide range
  of wavelengths, collectively referred to as the
  electromagnetic spectrum.
• Radio waves have the longest wavelengths, gamma
  rays have the shortest wavelengths.

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• All energy that Earth receives from the sun
  travels through space as electromagnetic
  radiation.
• Wavelengths in or close to the visible light
  range make up most of the energy given off by the
  sun.
• Some of this energy can pass through Earths
  atmosphere and reach Earths surface.

8

• Energy from the sun drives the water cycle and
  makes life possible on Earth.
• Energy from the sun is absorbed by Earths
  systems.
• This energy is then converted to thermal energy
  and transferred by convection and conduction.

9
Convection

• Most energy is moved through Earths systems by
  convection.
• Most convection occurs in fluids, such as water
  and air.
• Some convection can occur in solids that flow
  like putty.

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• The uneven heating of matter drives convection.
• Matter that is heated becomes less dense and
  rises. Cooler, denser matter sinks.
• The movement of matter that results from
  difference in density is called a convection
  current.

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• In the ocean, differences in temperature and
  salinity cause differences in density.
• Salinity is the amount of salt in salt water.
• Cold, salty water has a higher density than warm,
  less-salty water.

12

• In the ocean, convection causes deep currents.
• Deep currents are stream like movements of water
  far below the ocean surface.
• Deep currents take more than a thousand years to
  travel around the entire ocean.

13

• Convection currents in the atmosphere form when
  cold air sinks and forces warm air away from
  Earths surface.

14
Convection in the Geosphere

• Convection also occurs in the geosphere.
• Energy produced deep inside Earth heats rock in
  the mantle.
• The heated rock is under high pressure, so it
  becomes plastic without melting.

15

• The heated rock flows like putty.
• As it becomes less dense, the heated rock rises
  toward Earths surface.
• The cooler, denser rock surrounding the heated
  rock sinks.

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• In this way, heat inside Earth moves toward the
  cooler crust.
• This movement of rock is a convection current.
• Convection currents in the mantle cause the
  movement of tectonic plates.

17
Conduction

• When objects at different temperatures touch,
  their particles interact with each other.
• Fast-moving particles in the warmer object
  transfer energy to slower moving particles in the
  cooler substance.
• This causes the particles in the cooler substance
  to move faster and get warmer.

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• Energy can be transferred between the geosphere
  and the atmosphere by conduction.
• When Earths surface is warmer than the
  atmosphere, the ground will transfer energy to
  the atmosphere.
• When air comes into direct contact with the
  Earth, that energy is transferred by conduction.

19
Earths Energy Budget

• Energy on Earth moves through and between four
  spheres.
• These four spheres are open systems, which means
  they constantly exchange energy with each other.
• Energy is neither created nor destroyed.

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• It is simply transferred between spheres and
  converted into another form of energy.
• You can think of this movement of energy as part
  of an energy budget.
• An addition of energy in one sphere means a
  subtraction of energy in another.