The equator runs through Africa about halfway between the northern-most and southern-most points. Over three-quarters of Africa is in the tropics; only the upper part of the Sahara, the Mediterranean area, and the southern tip of Africa, are outside of the tropics. Because of being in the tropics, the snow line is much higher up than it would be on a mountain of similar height in the temperate zone. Africa is divided by the Sahara Desert, which stretches west to east just below the top of the continent. While some nomadic peoples live in the desert, and others live in the occasional oasis within the Sahara, the desert is mostly a vast barrier of sand, inhospitable and forbidding.