While mountains tend to look skinnier at the top when they are at the bottom - so basically like giant Isosceles triangles - they don't necessarily have more volume down towards their base. In fact, even the surface area of a mountain doesn't necessarily grow smaller the higher up you get, says the latest episode of MinutePhysics above, especially if that mountain happens to be part of a larger mountain range, which most mountains are.
Lone mountains with shapes like cones, spikes, or inverted parabolas tend to have less surface area the higher up you climb, says Henry Reich in the video, but a parabolic mountain will have significantly more area than a spikey mountain high up. And if you've got a really broad, flat mountain - sort of in the shape of a traditional loaf of bread - it can actually have more surface area the higher you go up, at least until you get to the very top, when things start to taper out again.
Ranges are even more complicated if you want to figure out how the surface area differs between the low regions and the high ones. "Some mountain ranges have less land area the higher you go up, some have more area, some have more then less, and some actually have more area at both the bottom and less area in the middle," says Henry.
In fact, a survey of all the mountain ranges in the world suggests that the more-then-less surface area model for mountain ranges is actually not so common. Most mountain ranges are actually bigger at their tops. How is this even possible? The latest episode of MinutePhysics has got all the answers above.