Tham khảo tài liệu 'earth sciences - notable research and discoveries part 6', khoa học tự nhiên, địa lý phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 100 EARTH SCIENCES Fossil fuel depletion high prices and environmental concerns motivate a search for clean renewable sources of energy. The problem thus far has been cost since fossil fuel alternatives tend to be more expensive despite the rising cost of fossil fuels. However one alternative lies beneath Earth s surface in a vast reservoir of heat in the planet s interior. People have been using this energy source for a long time albeit indi-rectly the planet s heat and pressure was necessary to cook the fossil fuels that are now so widely exploited. But a more direct use of Earth s heat geothermal energy may abound in the future if engineers and scientists can apply knowledge from the frontiers of Earth science to bring geothermal techniques into fruition. This chapter describes the successes that have been achieved and the research that aims to extend the use of geothermal energy even further. INTRODUCTION Earth s heat has two main sources. Part of the heat is left over from Earth s fiery creation about billion years ago. The other main contributor is radioactivity. Unlike the heat left over from Earth s formation radioactive decay of certain isotopes within the planet is an ongoing process adding more heat all the time. Some of the main sources of this heat are radioactive isotopes of uranium thorium and potassium. Heat flows or conducts through objects touching a hot stove is a bad idea because heat will flow from the stove to the skin resulting in a burned finger. Another mechanism of heat transfer is a convection current. Convection currents are flows of air or liquid that carry heat and are important in many of geological processes described in the three previous chapters. Radiation is also an important heat transfer mechanism. All objects radiate meaning that they emit electromagnetic radiation which is a form of energy. The type and amount of radiation depends on the object s temperature. Hot objects emit radiation having a high frequency such as .
