The earth is an open material system,
because it interchanges matter and energy with outer space.
- The terrestrial atmosphere continually loses
molecules, which drift off and it captures micrometeoroids (matter).
However, as time goes by, the mass of the planet has remained
practically constant.
- Of all the energy that reaches the earth, only 51%
reaches the surface of the planet. This energy is responsible for the
majority of the changes that take place on the surface of the planet.
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This apparently calm picture of the earth hides a great quantity of
dynamic change.
- The geographical relief is modified due to the action
of the wind and water, which are set in motion by solar energy.
- The energy that living beings use ultimately comes
from the sun.
- The atmosphere undergoes changes in its compostion
as a consequence of the action of living beings.
- Inside the earth, there is a great deal of energy
which is responsible for some geologic processes, such as volcanoes,
earthquakes, the formation of mountain ranges and the continental drift.
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The
greenhouse effect, which is described in the following film, consists
in a series of processes that prove this continual change.
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