Chapter 1.3

1. Chapter 1.3 The Energy Cycle

2. The Energy Cycle • The movement of energy into and out of the Earth system. • Different than the previous cycles we have learned about. • More like a scale. • When you measure on a scale you want the two sides to balance. • What is on one side should equal what is on the other side.

3. The Energy Cycle Continued… • The amount of energy entering a system should equal the amount of energy leaving a system. • If a system were to take in more energy than it released, the system would increase in temperature. • If it released more energy than it took in, temperatures would decrease. • Because of this balance-scale nature, scientists refer to the energy cycle as the energy budget • There are 3 main sources of energy in the energy budget: solar energy, geothermal energy, and tidal energy.

4. Solar Energy • Most of the energy that enters the Earth system(99.985%) system comes from the Sun. • Solar energy drives the winds, ocean currents, and waves. • It is also the source of the energy that causes rocks to weather and soil to form.

5. Geothermal Energy • Heat from within the Earth (0.013%) • Geothermal energy is responsible for driving the tectonic plates, powering volcanoes, geysers and earthquakes, and also contributes to rock formation.

6. Tidal Energy • Smallest part of the energy budget (0.002%) • Resuts from the sun and moon’s pull on the Earth’s oceans. • Powerful enough to slow Earth’s rotation because of the “tidal bulge”.

7. Maintaining the Balance • Incoming energy must go somewhere. • About 40% of it is reflected back into space. • Albedo • The percentage of energy that is reflected without being changed. • A forest has a low albedo (5-10% reflected). • A snow field has a high albedo (80-90% reflected).

8. The Laws of Thermodynamics • Energy follows predictable rules that explain what it will do. • Thermodynamics is the branch of physics that deals with how heat energy is converted into other forms of energy. • The laws of thermodynamics deals with how energy will flow.

9. First Law of Thermodynamics • Energy can never be created or destroyed, only changed from one form to another. • Example) • Solar energy is stored in plants which die and eventually become fossil fuels. • Fossil fuels are burned at electrical power plants and generate electricity, which can then power a light bulb.

10. Second Law of Thermodynamics • When energy changes, it is converted from a more useful, more concentrated form to a less useful, less concentrated form. • Unlike water which can convert from liquid to solid back to liquid without harm, energy cannot be recycled completely. • Some energy will always be lost, usually in the form of heat.