How were the 28km high Olympus Mons on Mars, formed?
Olympus Mons is a shield volcano and was probably formed from the same processes that produced the Hawaiian islands ( http://en.wikipedia.org/wiki/Hotspot_(geology )). The difference between here and Mars is that Mars has no plate tectonics. Here on Earth, the movement of plates moves the volcanoes out from above the hotspot. So, the hotspot has to keep creating new volcanoes. On Mars, the hotspot just kept pumping the lava out in the same place. So, it built up a monster of a mountain. http://www.exploringmars.com/science/olympus_mons.
