This volcano, the largest on Mars, measures over 600 km across at the base, and is about 27 km high. It is surrounded by a well defined scarp that is up to 6 km high.
Flows drape over the scarp and onto the surrounding plains.
In many places the scarp is associated with small block faults, indicating that faulting may have played a part in its development. Parts of the plains surrounding the volcano are characterized by ridged and grooved terrain that is faulted in places, The origin of this terrain is not known. The inset permits a greater appreciation of the structure of Olympus Mons, especially the caldera and the scarp. The caldera probably formed as a result of recurrent collapse following drainage of magma out of the central conduit of the volcano during flank eruptions. The floor of the deepest caldera is featureless at this resolution, but the floor materials of other parts of the caldera complex are marked by fault patters and ridges similar to mare ridges on the Moon.