How big were the eruptions? After all part of the reason why that thing is so big is that lack of plate tectonics which moves Hawaii islands away from the hot spot and because the amount of erosion is much less (look at how many obvious craters there are). Is Olympus Mons so big due to less erosion and no plate tectonics to move it away from a hot spot? Or is it so big because the eruptions really were that big? Or was it both?