Mars has mountains, valleys, and volcanoes, but the red planet's are by far the biggest and most dramatic.Recent and continuing missions to Mars are showing that the Red Planet may be more geologically active than previously thought.Olympus Mons, the solar system's largest volcano, towers some 16 miles above the Martian surface, making it three times taller than Everest.Geologists think one of the reasons volcanoes on Mars were able to grow so large is that Mars has fewer tectonic boundaries in comparison to Earth.
