A mountain is a landform that is characterized by high relief and by steeps slopes. Mountain cover about one-fifth of Earth's land surface.
That means that about one in five square miles of land is mountainous. For their inhabitants, mountains present special problems. Rough surfaces
and steep slopes make mountain travel difficult. Their elevation makes mountains colder than surrounding areas.

Most mountain do not stand alone. They are usually grouped together in mountain ranges. A mountain ranges is a chain of mountain peaks, ridges,
and valleys.