In a range of hills, or especially of
mountains, a 'pass' (also 'gap', 'notch', 'col', 'saddle', 'bwlch' or 'bealach') is a lower point that allows easier access through a range. On the route through the range, it is locally the highest point on the route. Since many of the world's mountain ranges have always presented formidable barriers to
travel, passes have been important since before recorded history, and have played a key role in
trade,
war and migration.
Topographically, a pass has the general form of a
saddle between two mountains (the elevation as a function of two position coordinates is mathematically a
saddle point). They are often found just above the source of a
river, constituting a sort of "bridge" over to the headwaters of a different river. Passes may be very short, consisting of steep
slopes to the top of the pass, or
valleys of many kilometers, whose highest point is only identifiable by
surveying.
Roads have long been built through passes, and more recently
railways. Some high and rugged passes may have
tunnels bored underneath, so as allow faster traffic flow year-round.
The top of a pass is frequently the only flat ground in the area, a high vantage point, so it is often a preferred site for buildings. For countries whose borders are delimited by a mountain range, the pass is typically part of the border, and the facilities likely include a
border control or
customs station, and possibly a military post as well. For passes with roads, it is also customary to have a small roadside sign giving the name of the pass and its
elevation above mean sea level.
There are thousands of named passes around the world; some are familiar names, such as the
Great St. Bernard Pass (2,473 m) in the
Alps, the
Khyber Pass (1,027 m) between
Afghanistan and
Pakistan, and the
Khardung La (5,359 m) in
Jammu and Kashmir,
India. The world's highest motorable pass may be the little known
Semo La (5,565 m) in
Tibet.
The word ''gap'' is more commonly used in the southern
Appalachians, while ''notch'' is more common in
New England.
In Scotland, the
Gaelic term ''bealach'' (anglicised "Balloch") is often used.
As well as allowing easier access between two valleys, a pass also similarly provides the route between two mountain tops with a minimum of descent, making it important also to hikers. Because of these advantages, it is common for tracks to meet at a pass, making them often convenient routes even when travelling between a summit and the valley floor.
Andes Mountains
Argentina and
Chile share the world's third longest international border, 5.300 km long, running from north to the south through the
Andes mountains. They share 42 mountain passes between them.
(see list)
See also
★
List of mountain passes
★
Principal passes of the Alps,
Ranges, Peaks and passes of the Alps