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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