Massif du Mont-Blanc (hiver panoramique).jpg

The Mont Blanc massif (french: Massif du Mont-Blanc; it, Massiccio del Monte Bianco) is a mountain range in the Alps, located mostly in France and Italy, but also straddling Switzerland at its northeastern end. It contains eleven major independent summits, each over in height. It is named after Mont Blanc (), the highest point in western Europe and the European Union. Because of its considerable overall altitude, a large proportion of the massif is covered by glaciers, which include the Mer de Glace and the Miage Glacierthe longest glaciers in France and Italy, respectively.

The massif forms a watershed between the vast catchments of the rivers Rhône and Po, and a tripoint between France, Italy and Switzerland; it also marks the border between two climate regions by separating the northern and western Alps from the southern Alps. The mountains of the massif consist mostly of granite and gneiss rocks and at high altitudes the vegetation is an arctic-alpine flora.

The valleys that delimit the massif were used as communication routes by the Romans until they left around the 5th century AD. The region remained of some military importance through to the mid-20th century. A peasant farming economy operated within these valleys for many centuries until the glaciers and mountains were "discovered" by the outside world in the 18th century. Word of these impressive sights began to spread, and Mont Blanc was first climbed in 1786, marking the start of the sport of mountaineering. The region is now a major tourist destination, drawing in over sixmillion visitors per year. It provides a wide range of opportunities for outdoor recreation and activities such as sight-seeing, hiking, rock climbing, mountaineering and skiing. Around one hundred people a year die across its mountains and, occasionally, bodies have been lost and entombed in its glaciers for decades.

Access into the mountains is facilitated by cable cars, mountain railways and mountain huts which offer overnight refuge to climbers and skiers. The long-distance Tour du Mont Blanc hiking trail circumnavigates the whole massif in an 11-day trek of . The Mont Blanc Tunnel connects the French town of Chamonix on the northern side with the Italian town of Courmayeur in the south. The high mountains have provided many opportunities for scientific research, including neutrino measurements within the tunnel and impact of climate change on its highest slopes. Recent rises in average temperatures have led to significant glacial retreat across the massif and an awareness of the need for better environmental protection, including a call for World Heritage Site status.

Geography

The Mont Blanc massif is long and lies in a southwest to northeasterly direction across the borders of France (Haute-Savoie and Savoie), Italy (Aosta Valley) and Switzerland (western Valais). At its widest point the massif is across.Distance measured from valley bottom to valley bottom, fro
French IGN online map
The northwestern side of the massif lies mostly within France, and is bounded by the valley of the Arve, containing the towns of Argentière and Les Houches. To the west it is bounded by the Val Montjoie, containing Les Contamines-Montjoie and the river Le Bon Nant which flows northwards to a confluence with the Arve near Saint-Gervais-les-Bains, and onwards to the Rhône.geographic detail also o
French IGN mapping portal
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The southern side of the massif lies mostly within Italy and is bounded by the Val Veny and Val Ferret whose watercourses meet just above Courmayeur. From Courmayeur these waters flow southwards as the Dora Baltea towards Aosta, eventually joining the Po. However, the extreme western end of the southern side of the massif does lie within France and is bounded by the Vallée des Glaciers (which connects to the Val Veny over the watershed of the col de la Seigne), and its waters flow southwards towards the Isère and onwards to the Rhône.

The northernmost section of the massif falls within Switzerland, and is bounded to the east by a separate valley, confusingly also called Val Ferret, and which separates it from the Pennine Alps. Its watercourse, la Dranse de Ferret, flows northwards to join the Rhône at Martigny. The west side of the northern end of the massif is drained by the Trient, also joining the Rhône near Martigny.

The borders of all three countries converge at a tripoint near the summit of Mont Dolent at an altitude of . From here the French – Italian border runs southwestwards along a ridge of high summits on the southern side of the massif, many of which are over in height, including the Grandes Jorasses, Rochefort Ridge, Dent du Géant, Mont Maudit, Mont Blanc and its western satellite, the Aiguille de Bionnassay. From here the border turns southwards over the Dômes de Miage and Aiguille de Tré la Tête before dropping down to the Col de la Seigne. North of Mont Dolent the border between France and Switzerland meanders roughly north-northwestwards along a ridge-line of slightly lower peaks, including the Aiguille d'Argentière, the Aiguille du Chardonnet and the Aiguille du Tour, before dropping down to the Col de Balme. The Swiss – Italian border runs southwest from Mont Dolent, down to the twin passes of Col Ferret.

The massif contains 11 main summits over in altitude, as well as numerous subsidiary points above this height. Crowning the massif is Mont Blanc (), the highest mountain in the Alps and in western Europe. From the summit of Mont Blanc to the Arve near Chamonix there is a drop in altitude over a distance of just . Because of its great elevation, much of the massif is snow- and ice-covered, and has been deeply dissected by glaciers. The Mer de Glace is the longest glacier in the range as well as the longest in France and the second longest in the Alps. The debris-covered Miage Glacier on the southern side of the massif is the longest in Italy.
The summit of Mont Blanc is an ice cap whose thickness varies from year to year.

The entire massif can be circumnavigated by the Tour du Mont Blanc, a walking route of approximately . It usually takes around 11 days to complete, but is also used for an annual mountain ultramarathon, with top competitors expected to complete the whole route in less than 21 hours.

The main mountain passes, or cols, that connect different valleys and towns around the Mont Blanc massif are:
*Col du Bonhomme (path, links Contamines – Beaufort – Les Chapieux)
*Col de la Seigne (path, links Bourg Saint Maurice – Les Chapieux – Courmayeur)
*Col Ferret (path, links Courmayeur – Orsières)
*Col de Champex and La Forclaz, or Fenêtre d'Arpette (path and road, links Orsières - Trient Valley)
*Col de Balme (path, links Trient Valley – Chamonix)
* Col de la Forclaz (major road, links Chamonix – Martigny)

Summits

File:French Alpes Ranskan Alpit 25.JPG, alt=mountaineers roped together on a glacier, Glacier travel – beginners learning the ropes on the Aiguille des Grands Montets
File:Aiguille des Glaciers - Glacier d'Estelette - Refuge Elisabetta.jpg, alt=Mountain with glacier and mountain hut below, Aiguille des Glaciers summit () bordering Italy and France, the watershed between the rivers Arve, Isère and Dora Baltea, and the site of a fatal plane crash in 1946
File:Alpinist on Mont Dolent.JPG, alt=man on summit of mountain wearing alpine climbing equipment, Alpinist on Mont Dolent summit (), a tripoint on the border between Italy, Switzerland and France
File:Pano gdmontets.JPG, alt=mountains of the Mont Blanc massif seen from the northeast, Panorama of the Mont Blanc massif from near the Aiguille des Grands Montets

The Mont Blanc massif includes eleven independent and six subsidiary summits over in height. These (including Mont Blanc) are shared between Italy and France only, the highest in Switzerland being the Aiguille d'Argentière. The massif is amongst the three major subranges of the Alps having the highest concentration of four-thousanders, together with the Pennine Alps and the Bernese Alps.

The first ascent of Mont Blanc in 1786 by Jacques Balmat and Michel Paccard initiated the sport of alpine mountaineering, and it was during the golden age of alpinism (185465) and the silver age of alpinism (186582) that the majority of the main summits of the massif were first attained. Members of the England-based Alpine Club were instrumental in many of the first ascents, usually accompanied by guides from Chamonix or Courmayeur, such as Michel Croz, Michel Payot and Émile Rey, as well as the Swiss guide, Christian Almer. Across the massif there are now more than two thousand different mountaineering routes to the summits, ranging greatly in both length and difficulty. These attract climbers from all over the world who, unlike the early ascensionists, now have access to numerous climbing guidebooks, modern safety equipment, good information on climbing routes and technical difficulty, as well as weather forecasts and mountain accommodation and food.

Glaciers

A wide range of glaciers and glacial structures can be found across the Mont Blanc massif, all of which can be easily reached or viewed. Glaciers cover of the massif, of which fall within France. The Mer de Glace is the largest glacier in the western Alps, and the second largest in Europe. It has a total length of from highest snowfield to terminus and an area of 35–40 km² (14–15 sq mi).

At around in length, the Miage Glacier is Italy's longest glacier and also the largest debris-covered glacier in Europe. Other large glaciers include the Argentière Glacier (), the Saleina Glacier (), Trient Glacier (), the Bossons Glacier ( ) and the Brenva Glacier. Whilst these glaciers appear to show similar fluctuations in length, research shows that each glacier of the Mont Blanc massif has its own individual and distinctive response time to changes in snowfall and climate. The Bossons Glacier is known to respond first, then the Argentière and the Trient Glaciers respond four to seven years later, with the Mer de Glace reacting last —between eleven and fifteen years after changes are first observed in the movement of ice in the Bossons Glacier.

Even the smallest glaciers can have a significant impact on the environment and on human activity. In 1892, a large body of water which had accumulated under the surface of the Tête Rousse Glacier, burst suddenly on the night of 11 July. It released of water and ice which flowed down the mountainside, killing 175 people in Saint-Gervais. The recent rediscovery of a further build-up of water deep within the glacier is now a cause of serious concern.

The inexorable downward movement and melting of glaciers can result in objects lost within them reappearing many years later.
The first recorded account of a body reappearing from a glacier in the Mont Blanc range was made by Viscount Edmond de Catelin in 1861. It concerned three alpine guides who were buried in a crevasse during an avalanche on 20 August 1820 near the Rocher Rouges, high up on Mont Blanc, during an expedition organised by . Forty years later the remains of two of them were discovered, re-exposed within fissures in the Bossons glacier. They were lower down from the point where they were lost; the corpse of the third guide was discovered the following year. In 2014, a group of climbers found a body on the Glacier du Talèfre, close to the Couvercle Hut. It was identified as that of a young Chamonix guide who had been caught in a winter storm during a solo ascent of the Nant Blanc face of the Aiguille Verte in 1982 and was assumed to have fallen into a crevasse. In 2013, a box of valuable gemstones was found by a climber on the Bossons Glacier. It had re-emerged, having been carried downhill from the site of one of two Air India plane crashes. These occurred at almost identical locations high up near the summit of Mont Blanc: one in 1950 (Air India Flight 245), and one in 1966 (Air India Flight 101). Debris from these crashes is still commonly found on the glacier below.

Geology

The Mont Blanc massif consists predominantly of ancient granite rocks. The Alps have their origins 770million years ago when upheaval of the earth's crust lifted up schist, gneiss and limestone rocks. These were destined to form the base of the Alps range, and this period of upheaval ended 300million years ago. Granite intrusions and associated metamorphic rocks formed the base of the mountains we now call the Mont Blanc massif as well as the nearby Aiguilles Rouges. But these rocks were then heavily eroded away, eventually being ground down and inundated by the sea, so allowing sedimentary rocks to form. Then, once again, this part of the earth's crust was uplifted as a result of the collision of continental plates. The huge mountain ranges of today's Alps began to form. This happened towards the end of the Tertiary period, 15million years ago. Finally, came the Quaternary era, when successive ice ages saw vast glaciers advance, retreat, and then advance again. Their movement across the landscape ground down and shaped the mountains and the valleys we see today.

Both the Mont Blanc massif, and the Aiguilles Rouges range to its north, now form part of the external zone of the Alps, effectively being the outermost layers of rock. The central granites make up Mont Blanc, the steep slopes of the Drus, the Grandes Jorasses and the Dent du Géant, and at the highest points are topped by schists, which are visible in places such as Grands Montets and near Mont Blanc's summit.

The granite mountains around Chamonix have been eroded into steep needle-shaped peaks (known as ). Known locally as ''protogine'', these rocks are lower in the mineral biotite mica and richer in quartz than the granites commonly found elsewhere.

A large part of the massif is covered by ice fields and is cut by numerous glaciers, mostly flowing northwestwards on the French side; southeastwards on the Italian side and eastwards on the Swiss side. With much steeper slopes on the Italian side, many glaciers drop very sharply and some, such as the Miage Glacier and the Brenva Glacier, are very heavily covered in rock debris. The massif is itself defined by broad valleys which formed along fault lines and which have subsequently been shaped by ice during the last glacial period of the ice age.

During the mid-19th century the granite of the Mont Blanc massif was an important source of stone for buildings; one hundred Italian stonemasons were brought to the Chamonix valley by Charles Albert of Sardinia for reconstructing the towns of Sallanches and Cluses, both of which had at that time just been destroyed by fires.

Minerals

The massif has been an important source of mineral specimens for crystal-hunters for over 250 years. The mountaineer and explorer, Edward Whymper, noted that the basin of the Glacier de Talèfre was "considered good hunting-ground for crystals", and that the slopes below les Courtes had yielded many large specimens. He recounted that in 1745 a guide had stated he had collected over of specimens there in just three hours.
The first systematic account of the minerals of the Mont Blanc area was published in 1873 by Venance Payot. His list, entitled "Statistique minéralogique des environs du Mt-Blanc", catalogued 90 mineral types although it also included those present only as very small components of rocks. If these are excluded, it is known today that at least 68 separate mineral species occur across the whole range of the Mont Blanc massif.

In order to preserve the mineralogical heritage of Mont Blanc, in 2008 the commune of Chamonix banned all mineral-hunting activities and collection of specimens without a prior permit being issued by the mayor's office. Use of explosives, heavy machinery or helicopters for removing material were also banned, and a code of practice put in place which requires an annual declaration of all finds to be made. It also gives a right for the Chamonix crystal museum (Musée des Cristaux) to have first option to acquire specimens of significance for its collections. To further protect the scientific value of material collected, all specimens offered for sale must be labelled with details of where they were found. The crystal museum opened to the public in 2006 and tells the story of the early crystal-hunters (known as ). Many specimens collected from across the massif are displayed there.

Climate

Located on the watershed between the Rhône and the Po, the Mont Blanc massif is also situated between the two different climatic regions of the northern and western Alps and that of the southern Alps. Climatic conditions on the Mer de Glace are similar to those found on the northern side of the Swiss Alps.

The climate of the Mont Blanc massif is cold and temperate (Köppen climate classification ''Cfb''), and is greatly influenced by altitude. The main valley settlements around the perimeter of the massif are at an altitude ranging between . Daytime valley temperatures in July and August may range up to , sometimes reaching . The greatest snowfall occurs between the months of November and April.

The best weather for mountaineering or hiking occurs between late June to early October but, being the highest part of the Alps, the Mont Blanc massif can create its own weather patterns. Temperatures drop as the mountains gain in height, and the summit of Mont Blanc is a permanent ice cap, with temperatures around . The summit is also prone to strong winds and sudden weather changes. Because of the massif's great overall height, a considerable proportion is permanently glaciated or snow-covered and is exposed to extremely cold conditions. Even on the high passes of the Tour du Mont Blanc, around , summer temperatures can be between , but feeling much colder because of wind chill in windy or wet conditions.

Precipitation is distributed fairly evenly over all months of the year, and mostly originates from a westerly airflow. There is, however, significant variation in precipitation with altitude. For example, Chamonix has an elevation of approximately and receives around of annual precipitation, whilst the Col du Midi, which is at above sea level, receives significantly more, totalling . However, at an even higher altitude (near to the summit of Mont Blanc) precipitation is considerably less, with only around recorded, despite the latter measurements being taken at a height of .

In the mountains further south of the Mont Blanc range, annual precipitation is significantly less than at equivalent altitudes within the massif. For example, the valleys in the Pelvoux massif at around receive only around of precipitation per year, which is significantly less than that in either Courmayeur or Chamonix.

Ecology

The massif contains a very rich variety of biodiversity as a result of the huge height range and different habitats found between the valleys and the highest summits. Mild temperatures occur at altitudes between , whereas arctic conditions occur from up to the highest point at .

Whilst the Mont Blanc massif does not contain any species that are endemic to it, there are many rare and legally protected species found within its four major habitat zones. These are the: montane forests, sub-alpine, alpine and nival zones. The major habitats are coniferous forests, moors, rock and talus slopes, plus glacial moraines. The biological richness is further influenced by the different aspects of the faces, by the geology, and by the influence of man on the lower and middle slopes where forest clearance has created open grassland. The native forest habitats are essential for the survival of many species, with the key conifer species including larch, pine, stone pine and red pine.

Flora

Over a thousand plant species have been recorded across the massif, from the valley bottoms right up to where the alpine chrysanthemum (') can be found at a record-breaking height.

Early explorers, such as Alexander von Humboldt in 1807, observed a number of notable species in the mountains around Mont Blanc at altitudes above . This was well above the permanent snow line, but on rocks that were so steep that little snow could rest. These arctic-alpine species included: '; '; '; ''Cardamine bellidifolia''; ''Draba hirta''; ' and ''Silene acaulis'' (occurring down to ). Between , Humboldt noted the following species of flowering plants amongst rocky debris around permanent snow fields and the highest alpine glaciers: '; '' Achillea atrata''; '' Gentiana nivalis''; '' Juncus trifidus''; '' Ranunculus glacialis''; ' and ''Saxifraga oppositifolia''.

In the mid-1800s, Venance Payot, a Chamonix naturalist, published a number of articles on the flora around the Mont Blanc area, including a list of the flowering plants, ferns mosses and lichens found at les Grands Mulets and elsewhere in the massif around Chamonix and the Aosta Valley.

High up in the middle of the Glacier de Talèfre, completely surrounded by ice, and due south of Les Droites, lies a large triangular region of steep mountainside containing an unusual mixture of high-alpine vegetation. Known as the ''Jardin de Talèfre'', its name derives from the rich assemblage of plants which occur at great altitude there (between ). Described as "one of the loftiest patches of vegetation in Europe upon an islet of rock in the midst of a wilderness of snow and ice", it is higher than the adjacent ground by tens of metres and, as a result, was spared glacial scouring and subsequent loss of its vegetation during the Little Ice Age (between 1300 and 1850). Nevertheless, it would at that time still have been surrounded by ice on all three sides, as evidenced by the three glacial moraines found there today.
Species recorded there include:
''Achillea nana'';
''Alchemilla pentaphylla'';
';
'' Arenaria serpyllifolia'';
''Cardamine alpina'';
''Draba frigida'';
''Empetrum nigrum'';
''Epilobium alpinum'';
';
'' Homogyne alpina'';
'' Jacobaea incana'';
''Juncus trifidus'';
'' Kalmia procumbens'';
';
';
''Ranunculus glacialis'';
';
'' Saxifraga aspera'';
'' Saxifraga bryoides'';
''Saxifraga oppositifolia'';
';
''Sibbaldia procumbens'' and
''Trifolium alpinum

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