A pass is a gap, or break, in high, rugged terrain such as a mountain ridge. A Mountain Pass forms when a glacier or stream erodes, or wears away, the land between areas of higher terrain. Passes often provide the easiest routes for people to travel across steep mountain ranges. For this reason, they have played an important role throughout human history in migration, trade, and settlement.
Most passes are flat at their summits and have the shape of a saddle. They can consist of very short, steep summits, or expansive valleys that stretch for kilometres. Often, passes sit just above the source of a river fed by precipitation and snowmelt.