Arête

An arête is a narrow ridge of rock which separates two valleys. It is typically formed when two glaciers erode parallel U-shaped valleys. Arêtes can also form when two glacial cirques erode headwards towards one another, although frequently this results in a saddle-shaped pass, called a col.[1] The edge is then sharpened by freeze-thaw weathering, and the slope on either side of the arete steepened through mass wasting events and the erosion of exposed, unstable rock.[2] The word ‘arête’ is actually French for edge or ridge; similar features in the Alps are described with the German equivalent term Grat.

Where three or more cirques meet, a pyramidal peak is created.

Striding Edge
Striding Edge, an arête viewed from Helvellyn with the corrie Red Tarn to the left and Nethermost Cove to the right
Vihren Pirin IMG 0859
View from the arête of Koncheto towards the southeast, with the peaks Kutelo and Vihren
Crib Goch, Snowdonia, Wales - August 2007
Crib Goch, Snowdonia, is an arête.
Cardiff Boundary arete
The arête between Big Cottonwood Canyon and Little Cottonwood Canyon, Utah, including Boundary Peak

Cleaver

A cleaver is a type of arête that separates a unified flow of glacial ice from its uphill side into two glaciers flanking, and flowing parallel to, the ridge. Cleaver gets its name from the way it resembles a meat cleaver slicing meat into two parts. A cleaver may be thought of as analogous to an island in a river. A common situation has the two flanking glaciers melting to their respective ends before their courses can bring them back together; the exceedingly rare analogy is a situation of the two branches of a river drying up, before the downstream tip of the island, by evaporation or absorption into the ground.

The location of a cleaver is often an important factor in the choice among routes for glacier flow. For example, following a cleaver up or down a mountain may avoid travelling on or under an unstable glacial, snow, or rock area. This is usually the case on those summer routes to the summit whose lower portions are on the south face of Mount Rainier: climbers traverse the ‘flats’ of Ingraham Glacier, but ascend Disappointment Cleaver and follow its ridgeline rather than ascending the headwall either of that glacier or (on the other side of the cleaver) of Emmons Glacier.

Examples

Notable examples of arêtes include:

See also

References

  1. ^ BBC bitesize
  2. ^ Orlove, Ben. "Glacier Retreat: Reviewing the Limits of Human Adaptation to Climate Change". Environment Magazine. Retrieved 30 September 2011.

External links

Aiguille de Rochefort

The Aiguille de Rochefort (4,001 m) is a mountain in the Mont Blanc massif in France and Italy. The peak lies on the Rochefort arête between the Dent du Géant and the Grandes Jorasses and is usually climbed during a traverse of the ridge.The first ascent of the peak was by James Eccles and guides Alphonse and Michel Payot on 14 August 1873.

Bastion Peak

Bastion Peak, at 13,500 feet (4,100 m), is located in the Wind River Range in the U.S. state of Wyoming. The peak is the ninth-highest in the range and the tenth-highest in Wyoming. The summit is located on the Continental Divide and the eastern slopes of the mountain are covered by a section of Gannett Glacier, the largest glacier in the American Rocky Mountains. An arête to the northeast leads to Bastion Peak-Northeast Peak, which, at 13,476 ft (4,107 m), is also one of the highest points in Wyoming.

Bastion Peak-Northeast Peak

Bastion Peak-Northeast Peak 13,476 ft (4,107 m) is located in the Wind River Range in the U.S. state of Wyoming. The peak is one of the highest in Wyoming, and is connected to its taller neighbor Bastion Peak by an arête to the southwest. An unnamed glacier lies below the precipitous east flank of the mountain, while Gannett Glacier is to the south.

Big Drift

The Big Drift is in Glacier National Park, in the U.S. state of Montana and is an area along the Going-to-the-Sun Road where a large amount of winter snow can accumulate to depths of 80 feet (24 m). Located immediately east of Logan Pass, the westerly winds push snow over the crest of the Continental Divide onto the eastern flank of a long arête which extends south from Pollock Mountain. West of the divide, this arête is known as the Garden Wall.

As spring approaches, the region is surveyed by helicopter in preparation for snow removal that will be needed in order to reopen the Going-to-the-Sun Road for the summer season. By early April, snow removal crews working from either end of the 53 miles (85 km) roadway have begun to ascend the steeper east and west slopes of the Lewis Range.

The area of the Big Drift is usually reached by late May, and it often can take a month to clear this one stretch of road that is slightly more than 1 mile (1.6 km) in length. Survey crews identify avalanche hazards and help to locate the road using global positioning equipment. Large cornices are usually removed using explosives, then excavators and front-end loaders move the snow over the cliffsides or into dump trucks.

The entire Going-to-the-Sun Road takes about ten weeks to plow, even with equipment that can move 4,000 short tons of snow an hour. By the first of June of each year, the Logan Pass visitor center can usually be reached by vehicle from at least one side of the Continental Divide. In 2011, due to abnormally heavy late winter and early spring snowfall, the Going-to-the-Sun Road did not open until July 13th, the latest opening ever due to snow.

Black Tooth Mountain

Black Tooth Mountain (13,009 feet or 3,965 metres) is located in the Bighorn Mountains in the U.S. state of Wyoming. The peak is the second highest in the range after Cloud Peak, which is only 1.5 miles (2.4 km) to the south, and the summit is located in the Cloud Peak Wilderness of Bighorn National Forest. The sharp dark profile of the mountain resembles a dark tooth or fang, hence the name. Because of the steep terrain, Black Tooth Mountain is one of the hardest mountains to climb in the Bighorns. Many of the trails up the mountain are unmarked which adds to the difficulty of reaching the summit. Mount Woolsey is an adjacent summit only .20 mi (0.32 km) to the southeast. Another high peak of the Bighorns known as Hallelujah Peak is situated along a knife-like ridge known as an arête .64 mi (1.03 km) to the northeast. Several tiny remnant glaciers can be found on the north slopes of Black Tooth Mountain.

Col

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.The height of a summit above its highest col (called the key col) is effectively a measure of a mountain's topographic prominence. Cols lie on the line of the watershed between two mountains, often on a prominent ridge or arête. For example, the highest col in Austria, the Obere Glocknerscharte ("Upper Glockner Col", 3,766 m (AA)), lies between the Kleinglockner (3,783 m above sea level (AA)) and Großglockner (3,798 m above sea level (AA)) mountains, giving the Kleinglockner a minimum prominence of 17 metres.The majority of cols are unnamed and are either never transited or only crossed in the course of negotiating a ridge line. Many double summits are separated by prominent cols. The distinction with other names for breaks in mountain ridges such as saddle, wind gap or notch is not sharply defined and may vary from place to place.

Crib Goch

Crib Goch is described as a ‘knife-edged’ arête in the Snowdonia National Park in Gwynedd, Wales. The name means ‘red ridge’ in the Welsh language.

The highest point on the arête is 923 metres (3,028 ft) above sea level. All routes which tackle Crib Goch are considered mountaineering routes in winter or scrambles in summer—meaning that they must cross ‘graded territory’ as defined in Steve Ashton's Scrambles in Snowdonia. The easiest of these lines (the ‘bad step’ part of the route) is given a scrambling grade of Grade 1 (the most difficult being Grade 3—routes more difficult than Grade 3 are considered rock climbs).

Càrn Mòr Dearg

Càrn Mòr Dearg (1,220 m (4,000 ft)) is the ninth-highest mountain in Scotland. It is situated in the west of Scotland, close to the town of Fort William, in Lochaber, Highland. It lies just to the north-west of its much more famous neighbour, Ben Nevis, to which it is linked by the spectacular Càrn Mòr Dearg Arête.

The ascent of Càrn Mòr Dearg from the north (start from the North Face Car Park), the traverse of the arête, and the scramble up the north side of Ben Nevis make one of the best horse-shoe routes in Scotland.

Garden Wall

The Garden Wall is a steep alpine area within Glacier National Park well known during the summer months to be heavily covered in dozens of species of flowering plants and shrubs. Located along the west side of the Continental divide and extending northward from Logan Pass, the Garden Wall can be traversed via the popular Highline Trail and for a distance of over 5 mi (8.0 km) to the Granite Park Chalet. The Going-to-the-Sun Road also passes through portions of the Garden Wall northwest of Logan Pass. The Weeping Wall is a short stretch of the Going-to-the-Sun Road where water cascades over the Garden Wall to the roadway below. The Garden Wall is an arête or rock spine that separates the Many Glacier region of the park from Lake McDonald valley.

Gem Glacier

Gem Glacier is the smallest named glacier in Glacier National Park (U.S.). Located on the east (Glacier County) side of the Continental Divide arête known as the Garden Wall, the glacier is situated on the cliff face above the better known Grinnell Glacier. Gem Glacier is a hanging glacier, and drapes down from the north face of the steep arete to which it is attached. Gem Glacier is only 5 acres (0.020 km2) in area and is far below the 25 acres (0.10 km2) threshold often cited as qualifying as an active glacier. Between 1966 and 2005, Gem Glacier lost 30 percent of its acreage and Grinnell Glacier lost 40 percent.

Hallelujah Peak

Hallelujah Peak (12,594 feet (3,839 m)), also known as Peak 12590, is located in the Bighorn Mountains in the U.S. state of Wyoming. The peak is the fifth-highest in the range and it is in the Cloud Peak Wilderness of Bighorn National Forest. Hallelujah Peak is 0.64 miles (1.03 km) northeast of Black Tooth Mountain and connected to that peak by a knife-like ridge known as an arête.

Jubiläumsgrat

The Jubiläumsgrat ("Jubilee Arête") or Jubiläumsweg ("Jubilee Way"), also nicknamed Jubi in climbing circles, is the name given to the climbing route along the arête between the Zugspitze (2,962 m) and the Hochblassen (2,706 m) (hence it is also called the Blassenkamm which means "Blassen Crest"). In front of its northwestern end, at the wind gap known as Falsche Grießkarscharte, climbers normally cross over to the Alpspitze (2,628 m) or down to the Matheisen cirque. Along the arête the three peaks of the Höllentalspitzen (2,740 m), the Vollkarspitze (2,630 m) and several rises have to be assailed or circumnavigated. The route is a serious, high Alpine tour and not, as often described, a Klettersteig.

List of Alpine four-thousanders

This list contains all of the 128 summits and subsidiary tops of 4,000 metres (13,123 ft) or more above sea level in the Alps in France, Italy and Switzerland as defined by the International Climbing and Mountaineering Federation (UIAA). Their list, published in 1994, contains 82 'official summits' of 4,000 m or over, with the inclusion of a further 46 'lesser summits' in an enlarged list. Another list containing only independent peaks with a prominence of over 100m contains just 52 mountains.

Mount Woolsey

Mount Woolsey (12,982 feet or 3,957 metres) is located in the Bighorn Mountains in the U.S. state of Wyoming. The peak is the third highest in the range after Cloud Peak, which is only 1.3 miles (2.1 km) to the south, and the summit is located in the Cloud Peak Wilderness of Bighorn National Forest. Black Tooth Mountain, the second highest mountain in the Bighorns, is an adjacent summit only .20 mi (0.32 km) to the northwest. Mount Woolsey is on a knife-like ridge known as an arête and is connected to both Black Tooth Mountain and Cloud Peak by this ridge. Along the arête is another mountain peak known as The Innominate. A small glacier lies below the arête to the southeast of Mount Woolsey.

Pointe Ronde

The Pointe Ronde is a mountain of the Mont Blanc massif, overlooking Trient in the canton of Valais. It lies near the northern end of the Arête de la Lys, the ridge descending in a north-westerly direction from the Génépi towards the Col de la Forclaz.

Swiftcurrent Glacier

Swiftcurrent Glacier is in Glacier National Park in the U.S. state of Montana.The glacier is on the east (Glacier County) side of the Continental Divide arête known as the Garden Wall. Swiftcurrent Glacier is one of several glaciers that are being monitored to determine stream flow alterations that occur due to glacial retreat. Compared to other glaciers in Glacier National Park, Swiftcurrent Glacier has experienced relatively slow retreat. As of 2005, the glacier had an area of 55 acres (0.22 km2), a 14 percent reduction since 1966.

The Innominate

The Innominate (12,761 feet or 3,890 metres) is a mountain peak located in the Bighorn Mountains in the U.S. state of Wyoming. Situated along a knife-like ridge known as an arête, the summit is located in the Cloud Peak Wilderness of Bighorn National Forest. The slightly taller Mount Woolsey is .30 miles (0.48 km) to the northwest. A small glacier lies below the arête to the east.

The Sawtooth

The Sawtooth is a jagged arête joining Mount Bierstadt to (eventually) Mount Evans in the Front Range of central Colorado. The three points along this arête resemble the teeth of a saw, leading to its name. The southeast wall of the arête is the head of the cirque above Abyss Lake, while its northwest wall is the cirque at the head of a valley above Guanella Pass. The northeast end of the sawtooth joins directly to the shoulder of Mount Spalding, from which a second (and slightly less abrupt) arête leads southeast to Mount Evans. This second arête divides the glacial valley of Abyss Lake to the southwest from the cirque of Summit Lake, to the northeast.

Wolfs Head

Wolfs Head is a (12,165-foot (3,708 m)) mountain located in the southern Wind River Range in the U.S. state of Wyoming. Wolfs Head is on the northwest side of the Cirque of the Towers, a popular climbing area. The peak is just north of Overhanging Tower and connected to Pingora Peak by a narrow arête. The East Ridge route on the Wolf's Head is recognized in the historic climbing text Fifty Classic Climbs of North America and considered a classic climb. Wolfs Head is situated on the Continental Divide.

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