Slide #2: Map of Tharsis Volcanic Region, Mars.

Mars is a world of volcanoes, canyons, craters, and dunes.  
It is a cold, arid planet that formed more than 4 and 1/2 
billion years ago.  The volcanoes of Mars come in a variety of 
sizes, the four big ones shown here are Olympus Mons (upper 
left), Arsia Mons (low center left), Pavonis Mons (center), 
and Ascraeus Mons (upper center right).  Other "small" 
volcanoes can also be seen here.  Olympus Mons is about 25 km 
(16 mi) high and is wide enough to cover the state of Arizona.  
The three volcano chain of Ascraeus-Pavonis-Arsia would stretch 
from Mexico to Canada along the U.S. west coast.  These 
volcanoes are among the youngest landforms on Mars; some may 
have been erupting less than a billion years ago. 

This shaded relief view is from the 1991 U.S. Geological Survey Map I-2160.

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