This question was submitted by Taylor at Windham Primary School, Maine. Travelling in our car at 60 miles per hour, it would take 165 days to make the trip. This question was submitted by Skip at Windham Primary School, Maine. There are several reasons why Olympus Mons and the other Martian volcanoes may be so large. One reason is that the magma chambers which fed the volcano are much larger and lie much deeper below the surface of Mars than magma chambers of volcanoes on Earth.
Deeper underground implies a higher pressure.
Also, the gravity on the surface of Mars is only about one third that of the Earth. This means it's easier for things to travel higher. Finally, on the Earth, the land floats on giant plates over the molten rock deep in the Earth. We don't believe this happened on Mars. Without the land moving above them, the hot spots can just keep building larger and larger volcanoes.