On the other hand, some obstacles might create a wind shadow where
wind speeds died down, creating an environment for deposition of
suspended particles. Thus, light-colored streaks formed. Figure
5.2 shows many light-colored wind streaks found at the base of the
Olympus Mons, a huge shield volcano in the Tharsis region.
High resolution images obtained by the Mars Global Surveyor show
that wind streaks can change over short period of time as indicated
in Figure 5.3. This image compares an area with repeated observations
obtained in August 1999 and April 2001. The white arrows show the
new wind streaks of the area that did not exist on the 1999 image.