Mountain pass

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Sani Pass in Lesotho. Sani Pass heading into Lesotho.jpg
Sani Pass in Lesotho.
A mountain pass as it appears on a contour map: Bwlch Maesgwm in Snowdonia, north Wales, United Kingdom. Bwlch Maesgwm contour map.png
A mountain pass as it appears on a contour map: Bwlch Maesgwm in Snowdonia, north Wales, United Kingdom.

A mountain pass is a navigable route through a mountain range or over a ridge. Since many of the world's mountain ranges have presented formidable barriers to travel, passes have played a key role in trade, war, and both human and animal migration throughout history. At lower elevations it may be called a hill pass.

Contents

Overview

Idealised mountain pass represented as the green line; the saddle point is in red. Saddleroute3.JPG
Idealised mountain pass represented as the green line; the saddle point is in red.

Mountain passes make use of a gap, saddle, col or notch. A topographic saddle is analogous to the mathematical concept of a saddle surface, with a saddle point marking the highest point between two valleys and the lowest point along a ridge. [2] [3] On a topographic map, passes are characterized by contour lines with an hourglass shape, which indicates a low spot between two higher points. [4]

Passes are often found just above the source of a river, constituting a drainage divide. A pass may be very short, consisting of steep slopes to the top of the pass, or may be a valley many kilometres long, whose highest point might only be identifiable by surveying.

Roads have long been built through passes, as well as railways more recently. Some high and rugged passes may have tunnels bored underneath a nearby mountainside (like the Eisenhower Tunnel bypassing Loveland Pass in the Rockies) to allow faster traffic flow throughout the year.

The top of a pass is frequently the only flat ground in the area, and is a high vantage point. In some cases this makes it a preferred site for buildings. If a national border follows a mountain range, a pass over the mountains is typically on the border, and there may be a border control or customs station, and possibly a military post as well. For instance Argentina and Chile share the world's third-longest international border, 5,300 kilometres (3,300 mi) long. The border runs north–south along the Andes mountains, with a total of 42 mountain passes. [5] [6] On a road over a pass, it is customary to have a small roadside sign giving the name of the pass and its elevation above mean sea level.

As well as offering relatively easy travel between valleys, passes also provide a route between two mountain tops with a minimum of descent. As a result, it is common for tracks to meet at a pass; this often makes them convenient routes even when travelling between a summit and the valley floor. Passes traditionally were places for trade routes, communications, cultural exchange, military expeditions etc. A typical example is the Brenner pass in the Alps.

Some mountain passes above the tree line have problems with snow drift in the winter. This might be alleviated by building the road a few meters above the ground, which will make snow blow off the road.

Synonyms

Col between Kensgriff and Yarlsidine in the Howgill Fells, England The col (6073968059).jpg
Col between Kensgriff and Yarlsidine in the Howgill Fells, England

There are many words for pass in the English-speaking world. In the United States, pass is very common in the West, the word gap is common in the southern Appalachians, notch in parts of New England, and saddle in northern Idaho. [7] The term col, derived from Old French, is also used, particularly in Europe.

Scotland has the Gaelic term bealach (anglicised "balloch"), while Wales has the similar bwlch (both being British Celtic languages). In the Lake District of north-west England, the term hause is often used, although the term pass is also common—one distinction is that a pass can refer to a route, as well as the highest part thereof, while a hause is simply that highest part, often flattened somewhat into a high-level plateau.

Around the world

There are thousands of named passes around the world, some of which are well-known, such as the Great St. Bernard Pass at 2,473 metres (8,114 ft) in the Alps, the Chang La at 5,360 metres (17,590 ft), and the Khardung La at 5,359 metres (17,582 ft) in Jammu and Kashmir, India. The roads at Mana Pass at 5,610 metres (18,410 ft) and Marsimik La at 5,582 metres (18,314 ft), on and near the China-India border respectively, appear to be world's two highest motorable passes. Khunjerab Pass between Pakistan and China at 4,693 metres (15,397 ft) is also a high-altitude motorable mountain pass. One of the famous but non-motorable mountain pass include Thorong La at 5,416 metres (17,769 ft) in Annapurna Conservation Area, Nepal.

See also

Related Research Articles

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Cime de la Bonette mountain in France

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Col The lowest point on a mountain ridge between two peaks

In geomorphology, a col is the lowest point on a mountain ridge between two peaks. It may also be called a gap. Particularly rugged and forbidding cols in the terrain are usually referred to as notches. They are generally unsuitable as mountain passes, but are occasionally crossed by mule tracks or climbers' routes. The term col tends to be associated more with mountain rather than hill ranges.

Bimberi Peak mountain

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San Francisco Pass mountain in Argentina

The San Francisco Pass is a pass over the Andes mountains which connects Argentina and Chile. The highest point of this pass is at 4,726 m (15,505 ft) AMSL.

Paso de Jama Mountain pass through the Andes

The Paso de Jama is a mountain pass through the Andes between Chile and Argentina, at an elevation of 4,200 m (13,800 ft) at the border.. It is the northernmost road border crossing between the two countries. The pass is reached via Chile Route 27 and via National Route 52 (Argentina). The Chile Route 27 reaches an altitude according to OpenStreetMap of 4,831 metres (15,850 ft) at 23°04′21″S67°30′17″W in a roaddistance of 57.6 kilometres (35.8 mi) west of the border, making it one of the highest highways in Southamerica.

Route des Crêtes road in France

Route des Crêtes is an 89 km (55 mi) road in the Vosges Mountains in eastern France, which passes through the Parc Naturel Régional des Ballons des Vosges. It connects Sainte-Marie-aux-Mines (north) with Cernay (south) and runs on the border of the departements of Haut-Rhin (68) and Vosges (88). Most of the route is at an elevation in excess of 950 m (3,117 ft), with the highest point being at the Col du Grand Ballon. The road is generally open from April to November, but most of the route is closed in the winter by snow.

Saddle (landform) region surrounding the highest point of the lowest point on the line tracing the drainage divide (the col) connecting the peaks

The saddle between two hills is the region surrounding the highest point of the lowest point on the line tracing the drainage divide connecting the peaks. When, and if, the saddle is navigable, even if only on foot, the saddle of a (optimal) pass between the two massifs, is the area generally found around the lowest route on which one could pass between the two summits, which includes that point which is a mathematically when graphed a relative high along one axis, and a relative low in the perpendicular axis, simultaneously; that point being by definition the col of the saddle.

Agua Negra Pass mountain pass between Chile & Argentina

The Agua Negra Pass is a pass over the Andes mountains which connects Argentina and Chile. The highest point of this pass is at 4,780 m (15,680 ft) AMSL.

Pircas Negras Pass

The Pircas Negras Pass is a pass over the Andes mountains which connects Argentina and Chile. The border crossing between Argentina and Chile is at 4,164 m (13,661 ft) AMSL.

Pichachen Pass gap in Argentina

The Pichachén Pass is a pass over the Andes mountains that connects Argentina and Chile. The border crossing between Argentina and Chile is at 2,060 m (6,760 ft) AMSL.

References

  1. 53°4′52.8″N4°7′57″W / 53.081333°N 4.13250°W , height contours from SRTM data.
  2. Eberhart, Mark E. (2004). Why Things Break: Understanding the World by the Way it Comes Apart. Random House. p. 232. ISBN   978-1-4000-4883-0 . Retrieved 6 November 2010.
  3. Bishop, Michael P.; Shroder, John F. (2004). Geographic Information Science and Mountain Geomorphology. Springer. pp. 86–87. ISBN   978-3-540-42640-0 . Retrieved 6 November 2010.
  4. Harvey, Mark William Thornton; Simer, Peter (1999). The National Outdoor Leadership School Wilderness Guide: The Classic Handbook. Simon & Schuster. p. 185. ISBN   978-0-684-85909-5 . Retrieved 6 November 2010.
  5. "Principales Pasos Nacionales e Internacionales – Estado de los Pasos Fronterizos" (in Spanish). Gendarmería Nacional Argentina. Archived from the original on 28 March 2010. Retrieved 4 March 2010.
  6. "Pasos - Chile" (in Spanish). Gendarmería Nacional Argentina. Archived from the original on 2007-07-18. Retrieved 4 March 2010.
  7. Map showing "saddle" names in Idaho

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