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There are two principal influences that shape the terrain :
constructive processes such as uplift, which create new
landscape features ,and destructive forces such as erosion,
which gradually wear away exposed landforms.
Carbon dioxide in the air reacts with the rainwater, forming a
weak acid (carbon acid) that may chemically attack the rocks.
The deserts,which already occupy approximately a fourth of the
Earth’s land surface,have in recent decades been increasing at
an alarming pace. The expansion of desertlike conditions into
area where they did not previously exist is called desertification.
It has been estimated that an additional one-fourth of the
Earth’s land surface is threatened by this process.
Ekman has found that the so-called Duchenne smile, which is
characterized by “crow’s feet” wrinkles around the eyes and a
subtle drop in the eye cover fold so that the skin above the eye
moves down slightly toward the eyeball, can lead to pleasant
feelings.
For example , people who believe that aggression is necessary
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