11.10 Heat and Soil

11.10 Heat and Soil

  • Much of life is dependent on biological activities near the surface of the soil.
    • In addition to plants, there are worms and insects whose lives are soil bound.
    • Micro organisms that are indispensable for the fertility of the soil are found in the soil.
    • The temperature of the soil is very important to this life.
  • The soil is heated by the sun.
    • The amount of heat from the molten core of the Earth is insignificant compared to solar heating.
    • The Earth is cooled by a number of factors.
    • Over the course of a year, the heating and cooling are balanced and the average temperature of the soil does not change.
    • The life cycles of the soil are affected by the temperature of the top soil over a short period of time.
  • The soil temperature is determined by the intensity of solar radiation, the composition of the soil, the vegetation cover, and the atmospheric conditions such as clouds, wind, and airborne particles.
    • Some patterns are general.
  • While the sun is shining, more heat is delivered to the soil than the cooling mechanisms can remove.
    • The temperature of the soil increases during the day.
    • The surface temperature can increase by 3 or 4 degrees.
    • In dry deserts the surface heating is very intense.
    • Some insects have evolved long legs to keep them out of the hot surface.
  • The heat goes deeper into the soil.
    • It takes some time for the heat to spread through the soil.
    • At a rate of 2 cm/h, a temperature change at the surface causes a soil change.
    • The heat that was stored in the soil during the day is no longer there.
    • While the surface is cooling off, a few centimeters below the surface, the temperature may still be rising.
    • Some animals take advantage of the lag in temperature between the surface and the interior of the soil.
    • They burrow into the ground to keep the temperature stable.
  • The thermal radiation emitted by the soil is reflected by the water and clouds in the spectrum.
  • Carbon dioxide, methane, and ozone are greenhouse gases in the atmosphere.
    • The gases absorb the radiation and send it back to the earth's surface.
  • An experiment that measured the rate of walking at 5 km/h up a 20* slope was designed.
  • The room has a volume of 27 m3.
    • Data is provided in the text.
  • A submarine has an oxygen tank that holds oxygen at a pressure of 100 atm.
  • We assume that the surface area remains the same.
  • A person with a height of 1.4 m and a weight of 60 kilograms would reduce her sleep by an hour a day.
  • Assume that a naked person is sitting on a chair that has 400 cm2 of skin in contact with aluminum.
    • The amount of heat transfer from the skin to the aluminum can be calculated if the skin temperature is 38*C and the aluminum is kept at 25*C. The heat conductivity of aluminum is very large.

  • A person takes about 20 breaths per minute.
    • The saturated exhaled air has a water vapor pressure of 24 torr.
  • The skin temperature should be 26*C.
  • Since ancient times, heat has been used for therapeutic purposes.
  • Muscle pain and arthritic conditions can be alleviated by local heating.
    • Discuss the effects of heat on tissue.