Explanation:
First picture (solo structure in desert): Wind. The wind has sculpted this by throwing grains of sand to the structure... it's a natural sandblasting job.
Second picture (rock and sea): Water. The constant waves hitting the rocks are sculpting and eroding it. I suspect some freezing and thawing (still water) was also into play.
Third picture (roots): vegetation. The roots of trees are very powerful and they'll destroy anything on their path seeking water.
Fourth picture (white and red): oxygen. That's a rusty piece of metal, the red comes from the oxydation, meaning blend of the metal with oxygen.
