Question: The Lötschenlücke connects the Lötschental to the valley of a glacier with a length of about what in 2014?

full_context: Document 1: Grison Alps: The Grison Alps are the mountains of the Graubünden canton of Switzerland (Grisons being the English name for the Graubünden region). There are many significant peaks in the Grison Alps, including the Tödi (3,614 m) and the highest peak, Piz Bernina (4,049 m). Many of the mountain ranges feature extensive glaciers, such as at the Adula, the Albula, the Silvretta, the Bernnina or the Rätikon range. The Grison Alps include parts of both the Eastern Alps and the Western Alps. The Eastern Alps located in Graubünden are the Rhaetian Alps, which is part to the Central Eastern Alps. The Rhaetian Alps consists of the following mountain ranges: Samnaun Alps, Rätikon, Silvretta, Sesvenna Range, Albula Range, Plessur Range, Oberhalbstein Range, Livigno Range, Bregaglia Range and the Bernina Range. The Western Alps located in Graubünden, include portions of the Lepontine Alps and the Glarus Alps.
Document 2: Alps: The Alps ( ; French: "Alpes" ] ; German: "Alpen" ] ; Italian: "Alpi" ] ; Romansh: "Alps" ; Slovene: "Alpe" ] ) are the highest and most extensive mountain range system that lies entirely in Europe, stretching approximately 1,200 km across eight Alpine countries: Austria, France, Germany, Italy, Liechtenstein, Monaco, Slovenia, and Switzerland. The mountains were formed over tens of millions of years as the African and Eurasian tectonic plates collided. Extreme shortening caused by the event resulted in marine sedimentary rocks rising by thrusting and folding into high mountain peaks such as Mont Blanc and the Matterhorn. Mont Blanc spans the French–Italian border, and at 4810 m is the highest mountain in the Alps. The Alpine region area contains about a hundred peaks higher than 4000 metres (just over 13,000 feet).
Document 3: Mer de Glace: The Mer de Glace is a valley glacier located on the northern slopes of the Mont Blanc massif, in the French Alps. It is 7.5 km long and 200 m deep but, when all its tributary glaciers are taken into account, it can be regarded as the longest and largest glacier in France, and the second longest in the Alps after the Aletsch Glacier.
Document 4: Jackson Glacier: Jackson Glacier is approximately the seventh largest of the remaining 25 glaciers in Glacier National Park located in the US state of Montana. A part of the largest grouping of glaciers in the park, Jackson Glacier rests on the north side of Mount Jackson. The glacier was most recently measured in 2005 at 250 acre , yet when first documented in 1850, the glacier also included the now separate Blackfoot Glacier and together, they covered 1875 acre . Between 1966 and 2005, Jackson Glacier lost almost a third of its acreage. When the two mountains were united prior to their separation sometime before 1929, they were known simply as Blackfoot Glacier. In 1850, there were an estimated 150 glaciers in the park. Glaciologists have stated that by the year 2030, many if not all of the glaciers in the park may disappear completely. Jackson and Blackfoot glaciers have been selected for monitoring by the U.S. Geological Survey's Glacier Monitoring Research program, which is researching changes to the mass balance of glaciers in and surrounding Glacier National Park. The glacier is being monitored using remote sensing equipment and repeat photography, where images of the glacier are taken from identical locations periodically. Jackson Glacier is one of the easiest of the park's glaciers to observe, and is located south of the Going-to-the-Sun Road on the east side of the Continental Divide, upper St. Mary Valley.
Document 5: Emmental Alps: The Emmental Alps (German: "Emmentaler Alpen" ) are a mountain range in the western part of the Alps, in Switzerland. They are located north-west of the Brünig Pass, mainly in the cantons of Lucerne, Bern, and Obwalden, with a small portion in the canton of Nidwalden. The highest summit of the range is the Brienzer Rothorn, which is also the highest point in the canton of Lucerne. The range is named after the Emme valley (German: Emmental). In the north-west corner one finds the relatively low, but widespread, and very furrowed Napf.
Document 6: Theodul Glacier: The Theodul Glacier (also spelled "Theodule Glacier"; German: "Theodulgletscher" ) is a glacier of the Alps, located south of Zermatt in the canton of Valais. It lies on the Swiss side of the Pennine Alps, although its upper basin touches the Italian region of the Aosta Valley. The glacier descends from the west side of the Breithorn (4164 m ) and splits into two diverging branches above Gandegg: the Upper Theodul Glacier ("Oberer Theodulgletscher"), spilling on a high plateau near Trockener Steg, together with the Furgg Glacier, and the Lower Theodul Glacier ("Unterer Theodulgletscher"), reaching a height of about 2500 m above the Gorner Glacier. Both branches are part of the Rhone basin, through the rivers Gornera, Mattervispa, and Vispa. Slightly above the glacier splitting is the Theodul Pass, crossing the border between Switzerland and Italy, and connecting Zermatt to Breuil-Cervinia. On the west, the Theodul Glacier is overlooked by the Matterhorn.
Document 7: Wildstrubel: The Wildstrubel (3244 m ) is a mountain of the Alps, straddling the border between the Swiss cantons of Bern and Valais. It forms a large glaciated massif, about 15 km wide, extending between the Rawil Pass and the Gemmi Pass. Along with the Muverans, the Diablerets and the Wildhorn, the Wildstrubel is one the four distinct mountain massifs of the Bernese Alps that lie west of the Gemmi Pass. The massif of the Wildstrubel is at the centre between the valleys of Simmental (BE), Engstligental (BE) and the Rhone (VS), the exact location of the tripoint being the summit of the Schneehorn. It comprises several distinct summits, including (from west to east) the Wetzsteinhorn, the Rohrbachstein, the Weisshorn, the Pointe de la Plaine Morte, Mont Bonvin, the Trubelstock and the Schneehorn. The main crest with the almost equally high summits of the Mittelgipfel (3,243.5 m) and the Grossstrubel (3,243 m) forms an amphitheatre oriented eastward which ends at the Steghorn and the Daubenhorn. This area encloses the Wildstrubel Glacier. To the southwest, the Wildstrubel overlooks the high glacier plateau of the Plaine Morte, which also includes an unnamed lake below the Schneehorn.
Document 8: Bietschhorn: The Bietschhorn (3,934 m) is a mountain in canton Wallis to the south of the Bernese Alps in Switzerland. The northeast and southern slopes of the mountain are part of the Jungfrau-Aletsch Protected Area (formerly "Jungfrau-Aletsch-Bietschhorn") listed as a UNESCO World Heritage Site that also includes the Jungfrau and the Aletsch Glacier. The Bietschhorn is located on the south side of the Lötschental valley and form part of the UNESCO World Heritage Region at the north end of the Bietschtal valley and Baltschiedertal valley. Most climbers approach the mountain from either the Bietschhornhütte or the Baltschiederklause.
Document 9: Breithorn (Blatten): The Breithorn (3,785 m) is a mountain of the Bernese Alps, located east of Blatten in the canton of Valais. It lies between the Bietschhorn and the Schinhorn, on the range separating the Lötschental (valley, north) from the main Rhone valley (south). Its summit is the tripoint between the Lötschental and two other smaller valleys: the Baltschiedertal and the valley of the Beichgletscher.
Document 10: Hollandia Hut: The Hollandia Hut (German: "Hollandiahütte") is a mountain hut of the Swiss Alpine Club, located east of Blatten in the canton of Valais. The hut lies at a height of 3,240 metres above sea level, just above the Lötschenlücke, the glacier pass connecting the Lötschental from the Aletsch Glacier. All accesses to the hut involve glacier crossing.
Document 11: Aletsch Glacier: The Aletsch Glacier (German: "Aletschgletscher" ) or Great Aletsch Glacier ("Grosser Aletschgletscher ") is the largest glacier in the Alps. It has a length of about 23 km (2014), has about a volume of 15.4 km3 (2011), and covers about 81.7 km2 (2011) in the eastern Bernese Alps in the Swiss canton of Valais. The Aletsch Glacier is composed of four smaller glaciers converging at Concordia Place, where its thickness was measured by the ETH to be still near 1 km . It then continues towards the Rhône valley before giving birth to the Massa. The Aletsch Glacier is – like most glaciers on this world – a retreating glacier. As of 2016, since 1980 it lost 1.3 km of its length, since 1870 3.2 km , and lost also more than 300 m of its thickness.
Document 12: Wildhorn: The Wildhorn is a mountain of the Alps, straddling the border between the Swiss cantons of Bern and Valais. At 3248 m above sea level, it is the highest summit of the Bernese Alps west of the Gemmi Pass. It forms a large glaciated massif, about 10 km wide, extending between the Sanetsch Pass and the Rawil Pass. Along with the Muverans, the Diablerets and the Wildstrubel, the Wildhorn is one the four distinct mountain massifs of the Bernese Alps that lie west of the Gemmi Pass. The massif of the Wildhorn is at the centre between the valleys of the Saane, Simme (both canton of Bern) and the Rhone (Valais). It comprises several distinct summits, including (from west to east) the Arpelistock, Le Sérac, the Geltenhorn, the Sex Noir, the Sex Rouge, the Schnidehorn and the Six des Eaux Froides. The main crest is between the glaciers named "Tungelgletscher" and "Glacier du Wildhorn". South of the main summit is the almost equally high summit of Mont Pucel (3,177 m). The Wildhorn is surrounded by several large mountain lakes: the Lac de Sénin, the Lauenensee, the Iffigsee, the Lac de Tseuzier and the Lac des Audannes. The Tungelgletscher, on the north-east face, was measured as 1.9 km in length in 1973.
Document 13: Dusty Glacier: Dusty Glacier is located on northeast slopes of Glacier Peak in the U.S. state of Washington. The glacier descends from 9022 ft to 6430 ft and in places along its length is connected to North Guardian Glacier which lies to its south and Ermine Glacier to the north. As is true with all the glaciers found on Glacier Peak, Dusty Glacier is retreating. During the Little Ice Age, Dusty Glacier extended down to an altitude of 4800 ft , but since approximately the year 1850, the glacier has been in a general state of retreat and has lost more than 1500 m of its length. Dusty Glacier is heavily crevassed and the glacier ends in an ice fall at its terminus.
Document 14: Lötschenlücke: The Lötschenlücke (el. 3164 m.) is a high mountain pass of the Bernese Alps, connecting the Lötschental to the valley of the Aletsch Glacier in the canton of Valais. Both sides of the pass are covered by glaciers: the Langgletscher on the west and the Grosser Aletschfirn on the east. The Lötschenlücke lies between the Mittaghorn on the north and the Sattelhorn on the south.
Document 15: Harrison Glacier: Harrison Glacier is located in the US state of Montana in Glacier National Park. Situated on a southeast facing ridge immediately south of Mount Jackson, Harrison Glacier is the largest glacier in Glacier National Park and was estimated in 2005 to have an area of 466 acre . Though many experts have stated that all the glaciers in Glacier National Park may disappear by the year 2030, Harrison Glacier lost only 9 percent of its surface area in the 40-year period between 1966 and 2005 and will likely still exist well beyond 2030. Compared to many of the vanishing glaciers in Glacier National Park, Harrison Glacier has a much higher altitude accumulation zone (approximately 9000 ft ) which has allowed it to maintain some equilibrium in its glacier mass balance. Comparing images of the glacier taken in 1913 with those from 2009, indicates that the glacier has experienced thinning and retreat.
ground_truth: 23 km