| Brenva Glacier | |
|---|---|
 View up the Brenva Glacier in July 2004, showing lower section completely covered with rock debris | |
  Brenva GlacierGlacier's location in the AlpsShow map of Alps Brenva GlacierBrenva Glacier (Northern Italy)Show map of Northern Italy | |
| Location | Northern slopes of the Mont Blanc massif |
| Coordinates | 45°49′43″N 6°53′56″E / 45.82861°N 6.89889°E / 45.82861; 6.89889 |
| Area | 7 square kilometres (2.7 sq mi) |
| Length | 6.7 km (4.2 mi) |
The Brenva Glacier (French: Glacier de la Brenva, Italian: Ghiacciaio della Brenva) is a valley glacier, located on the southern side of the Mont Blanc massif in the Alps. It is the second longest and eighth largest glacier in Italy, and descends down into Val Veny, close to Entrèves, near Courmayeur. Over the centuries it has experienced a number of major rock avalanches which have shaped the glacier and influenced its movement.
Description
The upper accumulation zones of the Brenva Glacier are enclosed by the Aiguille Noire de Peuterey, the Aiguille Blanche de Peuterey, Mont Blanc de Courmayeur, Mont Blanc, Mont Maudit, the Brenva Arête, the Tour Ronde, and the Aiguille de la Brenva.
The Brenva Glacier is formed from three branches, and descends steeply in a south-easterly direction, passing through a narrow neck (known as the Pierre à Moulin) at 2,460 to 2,550 metres (8,070 to 8,370 ft) above sea level (asl), and then falls sharply as a serac field, before reforming as a broad rock-covered glacial tongue. Since 2004, the lower section below the serac field has become completely separated from the upper section, resulting in the active front of the glacier now being at 2,350 m (7,710 ft) asl – some 1,000 metres (3,300 ft) higher than it was previously.
As at 1989, the Brenva Glacier had a maximum length of 7.64 km (4.75 mi), and an area of 8.06 km (3.11 sq mi), making it the eighth largest in Italy by area. Like most alpine glaciers, it has been retreating since that time, and is now approximately 6.7 km (4.2 mi) in length, but still remains the second longest. It has an area of approximately 7 km (2.7 sq mi) and, in its upper region, the glacier has a recorded speed of flow of 180 metres (590 ft) per year.
Rockfall and glacial advance
Minor rockfalls occur very frequently from the steep mountainsides above the Brenva Glacier.
On 18 January 1997 a major rockfall occurred at around 3,725 m (12,221 ft) which initiated an enormous avalanche that travelled 5.5 km (3.4 mi) horizontally, descending over 2,285 m (7,497 ft) into the floor of Val Veny. It killed two skiers and built a 25 m (82 ft)-high dam of snow and ice which temporarily blocked the Dora Baltea river, whilst the air blast destroyed mature forest trees and buildings on the opposite side of the valley. The total volume of rock, snow and ice was estimated at four million cubic metres. Further investigation suggested that the avalanche was not caused directly by the rockfall, but through seismic shock causing seracs to collapse which, in turn, then initiated the snow and ice avalanche. The rock avalanche itself has been described as a classic example of a sturzstrom.
The lower section of the Brenva Glacier is covered in rock – the remnants of earlier rockfalls in November 1920 from the east face of the Grand Pilier d'Angle. These were four separate events, consisting of between 2.4 to 3.6 million cubic metres of rock, which then mobilised a further 7.8 to 9.9 million cubic metres of snow and ice. Four additional pre-20th century rockfall events have also been identified on the Brenva Glacier. These occurred in 1767 AD; the early 14th century; between 426 and 615 AD; and between 2750 and 2350 calendar years BP.
Evidence for the glacier's re-advance in the past has been found in the form of ancient logs buried in moraine deposits. These indicate that those moraines themselves had once been exposed and forested, but then subsequently reburied by new moraines during another period of glacial advance.
Retreat of the Brenva Glacier since 1988 has exposed its lateral moraines which served to channel the massive 1997 rock avalanche between them. By contrast, earlier advance of the glacier that has started in 1913 served to raise the ice level above the moraines, thus causing the rock in that avalanche to come to rest outside of the moraines.
The major rockfall events on the Brenva Glacier have deposited so much rock debris that the normal balance between the upper accumulation zone and lower ablation zone has been compromised. For example, the 1920 rock avalanche added so much additional material to the already rock-covered lower zone, that ablation was significantly reduced. This effectively insulated that part of the glacier, resulting in its advance by an extra 490 metres between 1920 and 1941, and at a time when other glaciers nearby were retreating.
Brenva Bivouac hut
Located on a very large rock promontory between the upper branches of the glacier, the Brenva Bivouac (French: Bivouac de la Brenva) is a very small mountain refuge providing bivouac shelter for up to five people. It is at an altitude of approximately 3140 metres above sea level. Open all year round, it is not attended, and is owned by the Italian Alpine Club.
Access
The upper slopes of the Brenva Glacier can be reached via a col below the Tour Ronde, accessed from the Skyway Monte Bianco, but is only suitable for advanced freeride/snowboarders and skiers.
The old tongue of the glacier reaches down low into the Val Veni and is easily reached on foot from Entrèves or Courmayeur. It takes about six hours for alpine climbers to reach the Brenva Bivouac from Courmayeur.
See also
References
- ^ "3531 est" (Map). saint gervais les bains - mont-blanc (2nd ed.). 1:25,000. Carte Topographique (in French). Paris: Institut Géographique National. 1986.
- ^ "Brenva glacier | Aosta Valley". www.lovevda.it. Retrieved 2019-01-30.
- ^ Giani, Gian Paulo; Silvano, Sandro; Zanon, Georgio (2001). "Avalanche of 18 January 1997 on Brenva Glacier, Mont Blanc Group, Western Italian Alps: an unusual process of formation" (PDF). Annals of Glaciology. 32: 333–338. Bibcode:2001AnGla..32..333G. doi:10.3189/172756401781819157. Retrieved 5 February 2019.
- Cerutti, A.V. (2005). "The Brenva Glacier (Mt. Blanc, Alps) has lost its valley tongue". Geografia Fisica e Dinamica Quarternaria (Supplements of Physical Geography and Quaternary Dynamics). 28 (2): 229. Retrieved 5 February 2019.
- ^ Barbero, Rossana Serandrei; Zanon, Georgio (1989), "The Italian Alps", in Williams, R.S.; Ferrigno, J.G. (eds.), Satellite Image Atlas of Glaciers of the World - Glaciers of the Alps (PDF), U.S. Geological Survey Professional Paper 1386-H, U.S. Geological Survey, pp. E39, ISBN 978-0-607-71457-9
- Vivian, R. (2001). Des glaciers du Faucigny aux glaciers du Mont-Blanc. Montmélian: La Fontaine de Siloé. p. 296. ISBN 9782842061784.
- ^ Singh, Vijay P.; Singh, Pratap; Haritashya, Umesh K. (2011-06-29). Encyclopedia of Snow, Ice and Glaciers. Springer Science & Business Media. ISBN 9789048126422.
- "View a glacier: GLACIER "BRENVA"". www.nimbus.it. Retrieved 2019-02-04.
- ^ "Brenva glacier rock avalanche of 18 January 1997 on the Mount Blanc range, northwest Italy". ResearchGate. Retrieved 2019-02-04.
- ^ Deline, Philip (2001). "Recent Brenva rock avalanches (Valley of Aosta): New chapter in an old story?" (PDF). Supplementi di Geografia Fisica e Dinamica Quaternaria. V. ISSN 0391-9838. Retrieved 5 February 2019.
- Orombelli, Giuseppe (January 1982). "Late Holocene fluctuations of Brenva glacier ( Italian Alps)". ResearchGate. Retrieved 2019-02-06.
- "Brenva Bivouac | Aosta Valley". www.lovevda.it. Retrieved 2019-02-06.
- ^ "Bivouac de la Brenva 3060 m (cabane non gardée)". www.refuges.info. Retrieved 2019-02-06.
- Turismo, Courmayeur Mont Blanc. "itinerario, Ghiacciaio della Brenva - freeride, Luoghi - Itinerari, Courmayeur Mont Blanc vacanze in montagna, sci e alpinismo d'alta quota in estate ed inverno sul Monte Bianco - Valle d'Aosta Italy". www.courmayeurmontblanc.it/ (in Italian). Retrieved 2019-02-06.
- Vrinat, Stephane (2016-03-02). "Tour Ronde Brenva ski-alpinisme | Guides Saint-Gervais Mont-Blanc". Compagnie des Guides de Saint-Gervais Mont-Blanc (in French). Retrieved 2019-02-06.
Further reading
- Patrizia Imhof (2010) Glacier fluctuations in the Italian Mont Blanc massif from the Little Ice Age until the present, Master's Thesis, University of Bern.
External links
- Brenva Glacier on Google maps
- Castato Ghiacciai Archived 2017-10-22 at the Wayback Machine (Italian glacier mapping portal)