During the Martian Amazonian period this volcano was formed by eruption after eruption with successive layers of lava about 100 million years ago the lava had nowhere to go and with the low gravity system formed its massive base. Though it is not a wonder how it is formed or what it is, the reason it is still a wonder is if the planet were to somehow reverse its cold atmospheric effect with an infusion of greenhouse gases, would the volcano come back to life as some scientist believe it may still be active underneath its surface.