Energy in Earth Processes

• The thermosphere, the outermost part of Earth's atmosphere, has extremely high temperatures (thousands of degrees).

• Despite the high temperatures, a person would freeze to death if exposed to the thermosphere without a protective suit.

• This is because the density of atoms/molecules is very low, resulting in little thermal energy and available heat.

• An unprotected body would lose its thermal energy to the thermosphere.

Vocabulary

• condensation

• conduction

• convection

• crystallization

• electromagnetic energy

• electromagnetic spectrum

• energy

• heat energy

• joules

• mechanical energy

• nuclear decay

• radiation

• solidification

• specific heat

• temperature

• texture

• vaporization

• wavelength

Topic Overview

• Energy is the ability to do work and is a fundamental attribute of the universe.

• Earth operates as a machine driven by two major heat engines.

  • External Engine: Powered mainly by solar energy and drives most Earth surface processes.

  • Internal Engine: Powered by heat from Earth's interior, resulting in mechanical energy.

Electromagnetic Energy

• Electromagnetic energy is radiated in transverse waves from all matter not at absolute zero.

• Absolute zero is 0 Kelvin or -273° Celsius, the theoretically lowest possible temperature where particles have no motion.

• Visible light is a type of electromagnetic energy that is radiated by the sun and can be observed by the human eye.

• Transverse waves vibrate at right angles to their direction of movement.

Electromagnetic Spectrum

• Different types of electromagnetic energy are distinguished by their wavelengths.

• Wavelength: The distance from one crest of a wave to the next crest.

• Electromagnetic Spectrum: A model showing the various types of electromagnetic energy in order of increasing wavelength.

• Visible light is the only part of the electromagnetic spectrum that can be seen by the human eye.

• Infrared energy is often felt due to its heating effects.

• Instruments are needed to observe most forms of electromagnetic energy, such as ultraviolet energy.

• Long-wave electromagnetic energy has a wavelength longer than visible light.

• Short-wave electromagnetic energy has a wavelength shorter than visible light.

Interactions Between Electromagnetic Energy and an Environment

• When electromagnetic energy interacts with a material, the waves can be:

  • Refracted: Bent in their passage through materials of varying density, changing their direction.

  • Reflected: Bounced off the material.

  • Scattered: Refracted and/or reflected in various directions.

  • Transmitted: Passed through the material.

  • Absorbed: Taken into the material.

Surface Properties and Absorption

• Absorption characteristics of a surface determine how much electromagnetic energy is absorbed.

• Darker surfaces absorb more visible light, which is why dark asphalt feels hotter than light concrete on a sunny day.

• Color is the way the human eye distinguishes different wavelengths of visible light.

• Rougher surfaces absorb more energy and reflect less, while smoother surfaces (like mirrors) reflect more light.

• Materials that are effective at absorbing electromagnetic energy are also better at radiating it.

• Dark-colored objects heat up and cool down quickly, while light-colored objects heat up and cool down more slowly.

Transfer of Energy

• Energy moves from a region of high concentration (source) to a region of low concentration (sink).

• Heat energy: Energy transfer from a region of higher temperature to a region of lower temperature.

• Heat transfers thermal energy: The energy of the motions of atoms and molecules.

Achieving Dynamic Equilibrium

• Heat continues to move from source to sink until their energies are equal, establishing dynamic equilibrium.

• Dynamic Equilibrium: A state where a region loses and gains equal amounts of energy.

• If dynamic equilibrium is between all forms of energy, the temperature of the region or system will remain constant.

Methods of Energy Transfer

• Heat is transferred from an area of high concentration to an area of low concentration by one of three methods:

  • Conduction

  • Convection

  • Radiation

Conduction

• Conduction: The transfer of heat energy from atom to atom or molecule to molecule when vibrating atoms or molecules collide.

• Most effective in solids (especially metals) because atoms/molecules are closer together.

• Can also occur in liquids and gases.

Convection

• Convection: The transfer of heat by movement in fluids (gases and liquids) caused by differences in density.

• Warmer portions of the fluid usually have lower density and rise above cooler portions.

• Higher-density portions of a fluid are pulled down and displace less dense objects, pushing them upward.

• Convection Current: A circulatory motion that transfers heat energy from one place to another.

• Convection currents transfer heat throughout Earth's atmosphere, hydrosphere, and likely below the lithosphere.

Radiation

• Radiation: The method by which heat is transferred via electromagnetic waves.

• No medium is needed to transfer electromagnetic energy, allowing it to radiate across empty space.

• Radiation can also occur in liquids, solids, and gases.

• The higher an object's temperature, the more electromagnetic energy it gives off.

Transformation of Energy

• Transformation of energy: The changing of one type of energy into another type of energy.

Heat Production

• Transformations of energy often occur when there is friction.

• Example: Kinetic energy of a glacier transforms into heat energy due to friction between the glacier and valley walls.

• Another example: Wind blowing over the ocean creates waves and ocean currents, forming heat at the interface of the atmosphere and hydrosphere.

Transformations of Mechanical Energy

• Mechanical energy: All the energy of an object or system not related to the individual motions of atoms and molecules; the total of potential and kinetic energy.

• Kinetic energy: Energy of