Valles Marineris
Global View 

Valles Marineris is a canyon system that stretches 4,000 kilometers across, which is approximately the length of the United States.  The individual canyons can be as wide as 200 kilometers and as deep as 7.  The Grand Canyon, which is only 450 kilometers long, 30 kilometers wide, and 2 kilometers deep, is dwarfed by the Martian canyon system.

Planetary geologist believe that Valles Marineris was formed by several different causes. The western portion of the system is located on the Tharsis bulge.  The bulge is a rise in the surface that may have caused the surface to fracture.  The chaotic terrain at the eastern edge of the system suggests a collapsing of the surface.  While the dried-up channels that appear at the end of the chaotic terrain suggest water erosion.