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125-800: It is situated on the southwest flank of the Mont Blanc massif , flowing from the Bionnassay Pass (3,892 m (12,769 ft) above sea level ) in a generally southerly direction towards Val Veny . Its most northerly arm or tributary is the Glacier de Bionnassay italien , which arises from a cirque between the south eastern side of the Aiguille de Bionnassay, the Col de Bionnassay and the Calotte des Aiguille Grises. This descends for 2.5 km below

250-563: A basaltic magma to a granitic magma, but the quantities produced are small. For example, granitic rock makes up just 4% of the exposures in the South Sandwich Islands . In continental arc settings, granitic rocks are the most common plutonic rocks, and batholiths composed of these rock types extend the entire length of the arc. There are no indication of magma chambers where basaltic magmas differentiate into granites, or of cumulates produced by mafic crystals settling out of

375-749: 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 3,048 metres (10,000 ft) downhill from

500-483: 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

625-520: A diapir it would expend far too much energy in heating wall rocks, thus cooling and solidifying before reaching higher levels within the crust. Fracture propagation is the mechanism preferred by many geologists as it largely eliminates the major problems of moving a huge mass of magma through cold brittle crust. Magma rises instead in small channels along self-propagating dykes which form along new or pre-existing fracture or fault systems and networks of active shear zones. As these narrow conduits open,

750-610: A granite that is derived from partial melting of metasedimentary rocks may have more alkali feldspar, whereas a granite derived from partial melting of metaigneous rocks may be richer in plagioclase. It is on this basis that the modern "alphabet" classification schemes are based. The letter-based Chappell & White classification system was proposed initially to divide granites into I-type (igneous source) granite and S-type (sedimentary sources). Both types are produced by partial melting of crustal rocks, either metaigneous rocks or metasedimentary rocks. I-type granites are characterized by

875-565: A high content of sodium and calcium, and by a strontium isotope ratio, Sr/ Sr, of less than 0.708. Sr is produced by radioactive decay of Rb, and since rubidium is concentrated in the crust relative to the mantle, a low ratio suggests origin in the mantle. The elevated sodium and calcium favor crystallization of hornblende rather than biotite. I-type granites are known for their porphyry copper deposits. I-type granites are orogenic (associated with mountain building) and usually metaluminous. S-type granites are sodium-poor and aluminum-rich. As

1000-573: A large proportion of the massif is covered by glaciers , which include the Mer de Glace and the Miage Glacier  – the 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

1125-709: A meagre harvest of rye and oats . Some farmers in the valley of Chamonix joined their counterparts from the neighbouring valleys of Maurienne , Beaufortain and Tarentaise and crossed the Alps into southern Germany, Austria and northern Italy to sell their products and bring back goods for sale in local markets. In 1741, the Chamouny valley and its glaciers on the north side of the massif were discovered and written about by two aristocratic travelling Englishmen, named William Windham and Richard Pococke . The descriptions of their exploits were published across Europe, bringing

1250-824: A much higher proportion of clay with the Cecil soil series a prime example of the consequent Ultisol great soil group. Granite is a natural source of radiation , like most natural stones. Potassium-40 is a radioactive isotope of weak emission, and a constituent of alkali feldspar , which in turn is a common component of granitic rocks, more abundant in alkali feldspar granite and syenites . Some granites contain around 10 to 20 parts per million (ppm) of uranium . By contrast, more mafic rocks, such as tonalite, gabbro and diorite , have 1 to 5 ppm uranium, and limestones and sedimentary rocks usually have equally low amounts. Many large granite plutons are sources for palaeochannel -hosted or roll front uranium ore deposits , where

1375-579: 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

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1500-536: A peculiar mineralogy and geochemistry, with particularly high silicon and potassium at the expense of calcium and magnesium and a high content of high field strength cations (cations with a small radius and high electrical charge, such as zirconium , niobium , tantalum , and rare earth elements .) They are not orogenic, forming instead over hot spots and continental rifting, and are metaluminous to mildly peralkaline and iron-rich. These granites are produced by partial melting of refractory lithology such as granulites in

1625-568: A range of hills, formed by the metamorphic aureole or hornfels . Granite often occurs as relatively small, less than 100 km stock masses ( stocks ) and in batholiths that are often associated with orogenic mountain ranges. Small dikes of granitic composition called aplites are often associated with the margins of granitic intrusions . In some locations, very coarse-grained pegmatite masses occur with granite. Granite forms from silica-rich ( felsic ) magmas. Felsic magmas are thought to form by addition of heat or water vapor to rock of

1750-415: A result, they contain micas such as biotite and muscovite instead of hornblende. Their strontium isotope ratio is typically greater than 0.708, suggesting a crustal origin. They also commonly contain xenoliths of metamorphosed sedimentary rock, and host tin ores. Their magmas are water-rich, and they readily solidify as the water outgasses from the magma at lower pressure, so they less commonly make it to

1875-553: 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 200,000 cubic metres (7,100,000 cu ft) 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

2000-700: A small population of albino marmots within Val Ferret). Eurasian lynx have been reintroduced into the French Alps and, although present around the Mont Blanc massif, are extremely unlikely to be encountered. Over 80 different bird species have been recorded on the Italian side of the massif from within Val Ferret, including 63 nesting species and nine regional or national rarities. The following birds have been recorded in different habitats right across

2125-436: 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 170 kilometres (110 mi). The Mont Blanc Tunnel connects

2250-466: Is grus , which is often made up of coarse-grained fragments of disintegrated granite. Climatic variations also influence the weathering rate of granites. For about two thousand years, the relief engravings on Cleopatra's Needle obelisk had survived the arid conditions of its origin before its transfer to London. Within two hundred years, the red granite has drastically deteriorated in the damp and polluted air there. Soil development on granite reflects

2375-545: Is microgranite . The extrusive igneous rock equivalent of granite is rhyolite . Granitic rock is widely distributed throughout the continental crust . Much of it was intruded during the Precambrian age; it is the most abundant basement rock that underlies the relatively thin sedimentary veneer of the continents. Outcrops of granite tend to form tors , domes or bornhardts , and rounded massifs . Granites sometimes occur in circular depressions surrounded by

2500-517: Is 3–6·10 Pa·s. The melting temperature of dry granite at ambient pressure is 1215–1260 °C (2219–2300 °F); it is strongly reduced in the presence of water, down to 650 °C at a few hundred megapascals of pressure. Granite has poor primary permeability overall, but strong secondary permeability through cracks and fractures if they are present. A worldwide average of the chemical composition of granite, by weight percent, based on 2485 analyses: The medium-grained equivalent of granite

2625-571: 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 4,000 metres (13,123 ft) in height. It is named after Mont Blanc (4,808 metres (15,774 ft)), the highest point in western Europe and the European Union . Because of its considerable overall altitude,

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2750-447: 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: The Mont Blanc massif includes eleven independent and six subsidiary summits over 4,000 metres (13,123 ft) in height. These (including Mont Blanc) are shared between Italy and France only,

2875-504: Is an ice-contact lake near the southern end of the Miage Glacier, located on the outside of the glacier's 90-degree bend eastwards. It is a popular tourist attraction due to the spectacular ice cliffs rising up to one side and its two-coloured appearance. The colours reflect varying sediment concentrations in the water which arise as a result of the filtering effect of the debris. Huge ice blocks have been known to break off

3000-410: Is an excess of aluminum beyond what can be taken up in feldspars (Al 2 O 3 > CaO + K 2 O + Na 2 O) are described as peraluminous , and they contain aluminum-rich minerals such as muscovite . The average density of granite is between 2.65 and 2.75 g/cm (165 and 172 lb/cu ft), its compressive strength usually lies above 200 MPa (29,000 psi), and its viscosity near STP

3125-637: Is believed to have a mass of around 81 tonnes. It was the tallest temple in south India. Imperial Roman granite was quarried mainly in Egypt, and also in Turkey, and on the islands of Elba and Giglio . Granite became "an integral part of the Roman language of monumental architecture". The quarrying ceased around the third century AD. Beginning in Late Antiquity the granite was reused, which since at least

3250-434: Is called a binary or two-mica granite. Two-mica granites are typically high in potassium and low in plagioclase, and are usually S-type granites or A-type granites, as described below . Another aspect of granite classification is the ratios of metals that potentially form feldspars. Most granites have a composition such that almost all their aluminum and alkali metals (sodium and potassium) are combined as feldspar. This

3375-410: Is common in the continental crust of Earth, where it is found in igneous intrusions . These range in size from dikes only a few centimeters across to batholiths exposed over hundreds of square kilometers. Granite is typical of a larger family of granitic rocks , or granitoids , that are composed mostly of coarse-grained quartz and feldspars in varying proportions. These rocks are classified by

3500-532: 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 1,030 metres (3,380 ft) and receives around 1,020 mm (40 in) of annual precipitation, whilst the Col du Midi, which is at 3,500 metres (11,500 ft) above sea level, receives significantly more, totalling 3,100 mm (122 in). However, at an even higher altitude (near to

3625-404: 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. Over a thousand plant species have been recorded across

3750-439: 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

3875-433: Is limited by the amount of thermal energy available, which must be replenished by crystallization of higher-melting minerals in the magma. Thus, the magma is melting crustal rock at its roof while simultaneously crystallizing at its base. This results in steady contamination with crustal material as the magma rises. This may not be evident in the major and minor element chemistry, since the minerals most likely to crystallize at

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4000-505: Is located at 2,173 m (7,129 ft) above sea level, and is the highest botanical garden in Europe. It contains around 800 plant species and covers an area of 7,000 square metres (75,000 sq ft). It was originally created in 1987 just as a tourist attraction but, with the subsequent designation of the adjacent Pavillon du Mont Frety as a protected area, it has since increased in scientific importance. It can be reached either from

4125-401: Is located has been occupied by humans for at least 70,000 years, although, as now—and because of the great height and glaciated nature of the mountains—only the lower parts of the valleys around its perimeter would have been inhabited or used as routes of communication. The Romans, who occupied the region 2,000 years ago, used the main valleys around the massif for military purposes. They gave

4250-404: Is permeated by sheets and channels of light granitic rock (the leucosome ). The leucosome is interpreted as partial melt of a parent rock that has begun to separate from the remaining solid residue (the melanosome). If enough partial melt is produced, it will separate from the source rock, become more highly evolved through fractional crystallization during its ascent toward the surface, and become

4375-454: Is relieved when overlying material is removed by erosion or other processes. Chemical weathering of granite occurs when dilute carbonic acid , and other acids present in rain and soil waters, alter feldspar in a process called hydrolysis . As demonstrated in the following reaction, this causes potassium feldspar to form kaolinite , with potassium ions, bicarbonate, and silica in solution as byproducts. An end product of granite weathering

4500-401: Is significantly less than that in either Courmayeur or Chamonix. 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 600 and 1,000 metres (2,000 and 3,300 ft), whereas arctic conditions occur from 2,500 metres (8,200 ft) up to

4625-411: Is some concern that some granite sold as countertops or building material may be hazardous to health. Dan Steck of St. Johns University has stated that approximately 5% of all granite is of concern, with the caveat that only a tiny percentage of the tens of thousands of granite slab types have been tested. Resources from national geological survey organizations are accessible online to assist in assessing

4750-479: Is that magma will rise through the crust as a single mass through buoyancy . As it rises, it heats the wall rocks , causing them to behave as a power-law fluid and thus flow around the intrusion allowing it to pass without major heat loss. This is entirely feasible in the warm, ductile lower crust where rocks are easily deformed, but runs into problems in the upper crust which is far colder and more brittle. Rocks there do not deform so easily: for magma to rise as

4875-410: Is the case when K 2 O + Na 2 O + CaO > Al 2 O 3 > K 2 O + Na 2 O. Such granites are described as normal or metaluminous . Granites in which there is not enough aluminum to combine with all the alkali oxides as feldspar (Al 2 O 3 < K 2 O + Na 2 O) are described as peralkaline , and they contain unusual sodium amphiboles such as riebeckite . Granites in which there

5000-459: Is typically orthoclase or microcline and is often perthitic . The plagioclase is typically sodium-rich oligoclase . Phenocrysts are usually alkali feldspar. Granitic rocks are classified according to the QAPF diagram for coarse grained plutonic rocks and are named according to the percentage of quartz , alkali feldspar ( orthoclase , sanidine , or microcline ) and plagioclase feldspar on

5125-428: Is uncommon, is classified simply as quartz-rich granitoid or, if composed almost entirely of quartz, as quartzolite . True granites are further classified by the percentage of their total feldspar that is alkali feldspar. Granites whose feldspar is 65% to 90% alkali feldspar are syenogranites , while the feldspar in monzogranite is 35% to 65% alkali feldspar. A granite containing both muscovite and biotite micas

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5250-494: 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 4,000 metres (13,123 ft) in altitude, as well as numerous subsidiary points above this height. Crowning the massif is Mont Blanc (4,808 metres (15,774 ft)),

5375-663: The Col Infranchissable then turns south-east to merge with other glaciers, thence continuing as the Miage glacier. At around 10 km (6.2 mi) in length, the Miage Glacier is Italy's longest glacier and also the largest debris-covered glacier in Europe. Approximately 5 km (1.9 sq mi) of its total area of ~11 km (4.2 sq mi) is covered in debris originating primarily in rockfall from surrounding walls and avalanching in accumulation areas of its four tributaries . Debris carried along within

5500-559: 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

5625-508: The Jardin de Talèfre , its name derives from the rich assemblage of plants which occur at great altitude there (between 2,650 and 3,000 m (8,690 and 9,840 ft)). 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

5750-1030: 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 biflora  [ de ] ; Arenaria serpyllifolia ; Cardamine alpina ; Draba frigida ; Empetrum nigrum ; Epilobium alpinum ; Helictotrichon versicolor  [ pl ] ; Homogyne alpina ; Jacobaea incana ; Juncus trifidus ; Kalmia procumbens ; Poa laxa  [ pl ] ; Potentilla frigida  [ de ] ; Ranunculus glacialis ; Ranunculus pyrenaeus  [ de ] ; Saxifraga aspera ; Saxifraga bryoides ; Saxifraga oppositifolia ; Sedum alpestre  [ es ] ; Sibbaldia procumbens and Trifolium alpinum . The Saussurea Alpine Botanical Garden above Courmayeur

5875-739: 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

6000-586: The silver age of alpinism (1865–82) 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

6125-404: The terminus . Patchy areas can occur, however, where crevasses or moulins occur. Debris thickness generally increases from a few centimetres at 2,400 m (7,900 ft) asl to over 1 metre (3 ft 3 in) at the terminus at ~1,775 m (5,823 ft) asl, although the spatial distribution of thicknesses is heterogeneous especially on parts of the northern terminal lobe. Miage Lake

6250-593: The 5th century AD, they had left completely. The areas left behind were occupied in the western part by the Burgundian tribes from what is today France, whilst the Alemanni tribes from Germany moved into eastern parts, resulting in the linguistic divide found today across the Alps. For many centuries thereafter, the settlements around the Mont Blanc massif comprised a rural population of peasant mountain farmers, living off animal husbandry , supplemented with

6375-571: The A-Q-P half of the diagram. True granite (according to modern petrologic convention) contains between 20% and 60% quartz by volume, with 35% to 90% of the total feldspar consisting of alkali feldspar . Granitic rocks poorer in quartz are classified as syenites or monzonites , while granitic rocks dominated by plagioclase are classified as granodiorites or tonalites . Granitic rocks with over 90% alkali feldspar are classified as alkali feldspar granites . Granitic rock with more than 60% quartz, which

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6500-433: 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. 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

6625-615: The European Union safety standards (section 4.1.1.1 of the National Health and Engineering study) and radon emission levels well below the average outdoor radon concentrations in the US. Granite and related marble industries are considered one of the oldest industries in the world, existing as far back as Ancient Egypt . Major modern exporters of granite include China, India, Italy, Brazil, Canada, Germany, Sweden, Spain and

6750-455: 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

6875-486: 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

7000-657: The Miage Glacier is Italy's longest glacier and also the largest debris-covered glacier in Europe. Other large glaciers include the Argentière Glacier (9 km (5.6 mi)), the Saleina Glacier (6 km (3.7 mi)), Trient Glacier (4 km (2.5 mi)), the Bossons Glacier ( c. 4 km (2.5 mi)) and the Brenva Glacier. Whilst these glaciers appear to show similar fluctuations in length, research shows that each glacier of

7125-639: The Mohs hardness scale) , and tough. These properties have made granite a widespread construction stone throughout human history. The word "granite" comes from the Latin granum , a grain, in reference to the coarse-grained structure of such a completely crystalline rock. Granitic rocks mainly consist of feldspar , quartz , mica , and amphibole minerals , which form an interlocking, somewhat equigranular matrix of feldspar and quartz with scattered darker biotite mica and amphibole (often hornblende ) peppering

7250-599: 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

7375-496: The Mont Blanc massif, all of which can be easily reached or viewed. Glaciers cover 170 square kilometres (66 sq mi) of the massif, of which 110 km (42 sq mi) 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 12 km (7.5 mi) from highest snowfield to terminus and an area of 35–40 km (14–15 sq mi). At around 10 km (6 mi) in length,

7500-471: The Mont Blanc massif: Seven of the massif's largest indigenous mammal species are housed in the Merlet Animal Park near Les Houches, including ibex, chamois, marmot, fallow and roe deer . Located 600 metres (2,000 ft) above the village, the park was founded in 1968 and contains eighty animal species from mountain habitats around the world. The region in which the Mont Blanc massif

7625-533: The Rocher Rouges, high up on Mont Blanc, during an expedition organised by Joseph Hamel  [ de ] . Forty years later the remains of two of them were discovered, re-exposed within fissures in the Bossons glacier. They were 3,000 metres (9,800 ft) 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

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7750-642: The Tour of Mont Blanc. When Savoy was eventually annexed to France in 1860, Napoleon III and Empress Eugénie visited the region to mark the event and undertook to enhance road access leading to the end of the Arve valley. The 19th century saw considerable economic development which turned the small agricultural town of Chamonix into a base for tourists, with luxurious hotels and mountain lodges being built to accommodate them. A trade in selling local items to visiting foreigners soon developed. Crystals collected from across

7875-511: The United States. The Red Pyramid of Egypt ( c.  2590 BC ), named for the light crimson hue of its exposed limestone surfaces, is the third largest of Egyptian pyramids . Pyramid of Menkaure , likely dating 2510 BC, was constructed of limestone and granite blocks. The Great Pyramid of Giza (c. 2580 BC ) contains a huge granite sarcophagus fashioned of "Red Aswan Granite". The mostly ruined Black Pyramid dating from

8000-436: The accumulated steeps; Amongst many other notable visitors were: Goethe (1779); Chateaubriand (1805); Madame de Staël ; Victor Hugo ; Louis Pasteur and Franz Liszt (1836), plus two successive wives of Napoleon Bonaparte : Joséphine de Beauharnais (1810) and Marie Louise of Austria (1814). In 1849, John Ruskin spent a month in Chamonix, from where he painted some of the massif's mountains before undertaking

8125-419: The base of the chamber are the same ones that would crystallize anyway, but crustal assimilation is detectable in isotope ratios. Heat loss to the country rock means that ascent by assimilation is limited to distance similar to the height of the magma chamber. Physical weathering occurs on a large scale in the form of exfoliation joints , which are the result of granite's expanding and fracturing as pressure

8250-418: The big difference in rheology between mafic and felsic magmas makes this process problematic in nature. Granitization is an old, and largely discounted, hypothesis that granite is formed in place through extreme metasomatism . The idea behind granitization was that fluids would supposedly bring in elements such as potassium, and remove others, such as calcium, to transform a metamorphic rock into granite. This

8375-404: The division between S-type (produced by underplating) and I-type (produced by injection and differentiation) granites, discussed below. The composition and origin of any magma that differentiates into granite leave certain petrological evidence as to what the granite's parental rock was. The final texture and composition of a granite are generally distinctive as to its parental rock. For instance,

8500-473: The early 16th century became known as spolia . Through the process of case-hardening , granite becomes harder with age. The technology required to make tempered metal chisels was largely forgotten during the Middle Ages. As a result, Medieval stoneworkers were forced to use saws or emery to shorten ancient columns or hack them into discs. Giorgio Vasari noted in the 16th century that granite in quarries

8625-448: 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 300   million 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

8750-579: The first magma to enter solidifies and provides a form of insulation for later magma. These mechanisms can operate in tandem. For example, diapirs may continue to rise through the brittle upper crust through stoping , where the granite cracks the roof rocks, removing blocks of the overlying crust which then sink to the bottom of the diapir while the magma rises to take their place. This can occur as piecemeal stopping (stoping of small blocks of chamber roof), as cauldron subsidence (collapse of large blocks of chamber roof), or as roof foundering (complete collapse of

8875-409: The following species of flowering plants amongst rocky debris around permanent snow fields and the highest alpine glaciers: Achillea nana  [ fr ] ; Achillea atrata ; Gentiana nivalis ; Juncus trifidus ; Ranunculus glacialis ; Saxifraga biflora  [ de ] and Saxifraga oppositifolia . In the mid-1800s, Venance Payot , a Chamonix naturalist , published

9000-510: The glacier and fall into the lake, providing another major tourist attraction despite the low chance of such an event occurring. On August 7, 1996, a particularly large block, estimated to have had a volume of 7000-16000m, fell into the lake causing an abnormally large wave that seriously injured several people. The incident was caught on camera by at least one tourist. Mont Blanc massif The Mont Blanc massif ( French : Massif du Mont-Blanc ; Italian : Massiccio del Monte Bianco )

9125-407: The glacier is also being exposed at increased rates due to accelerating thinning of the glacier tongue. The number of sources of supraglacial debris as well as the unusual, mica schist -dominated lithology of the rock walls surrounding the glacier, makes for a varied debris lithology; debris cover becomes continuous at ~2,400 m (7,900 ft) above mean sea level (asl) and remains unbroken to

9250-423: 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

9375-519: 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 six   million 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

9500-713: The grotto is a highly regarded piece of Buddhist art , and along with the temple complex to which it belongs, Seokguram was added to the UNESCO World Heritage List in 1995. Rajaraja Chola I of the Chola Dynasty in South India built the world's first temple entirely of granite in the 11th century AD in Tanjore , India . The Brihadeeswarar Temple dedicated to Lord Shiva was built in 1010. The massive Gopuram (ornate, upper section of shrine)

9625-600: 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 (1854–65) and

9750-414: The highest mountain in the Alps and in western Europe. From the summit of Mont Blanc to the Arve near Chamonix there is a 3,800 metres (12,500 ft) drop in altitude over a distance of just 8 kilometres (5.0 mi). 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

9875-432: The highest point at 4,808 metres (15,774 ft). 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

10000-911: The landscape ground down and shaped the mountains and the valleys as seen 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 aiguilles ). Known locally as protogine , these rocks are lower in

10125-570: The lighter color minerals. Occasionally some individual crystals ( phenocrysts ) are larger than the groundmass , in which case the texture is known as porphyritic . A granitic rock with a porphyritic texture is known as a granite porphyry . Granitoid is a general, descriptive field term for lighter-colored, coarse-grained igneous rocks. Petrographic examination is required for identification of specific types of granitoids. Granites can be predominantly white, pink, or gray in color, depending on their mineralogy . The alkali feldspar in granites

10250-478: 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 170 kilometres (110 mi). It usually takes around 11 days to complete, but

10375-474: The lower crust , rather than by decompression of mantle rock, as is the case with basaltic magmas. It has also been suggested that some granites found at convergent boundaries between tectonic plates , where oceanic crust subducts below continental crust, were formed from sediments subducted with the oceanic plate. The melted sediments would have produced magma intermediate in its silica content, which became further enriched in silica as it rose through

10500-729: The lower continental crust at high thermal gradients. This leads to significant extraction of hydrous felsic melts from granulite-facies resitites. A-type granites occur in the Koettlitz Glacier Alkaline Province in the Royal Society Range, Antarctica. The rhyolites of the Yellowstone Caldera are examples of volcanic equivalents of A-type granite. M-type granite was later proposed to cover those granites that were clearly sourced from crystallized mafic magmas, generally sourced from

10625-435: The magma is inevitable once enough magma has accumulated. However, the question of precisely how such large quantities of magma are able to shove aside country rock to make room for themselves (the room problem ) is still a matter of research. Two main mechanisms are thought to be important: Of these two mechanisms, Stokes diapirism has been favoured for many years in the absence of a reasonable alternative. The basic idea

10750-426: The magma. Other processes must produce these great volumes of felsic magma. One such process is injection of basaltic magma into the lower crust, followed by differentiation, which leaves any cumulates in the mantle. Another is heating of the lower crust by underplating basaltic magma, which produces felsic magma directly from crustal rock. The two processes produce different kinds of granites, which may be reflected in

10875-408: The magmatic parent of granitic rock. The residue of the source rock becomes a granulite . The partial melting of solid rocks requires high temperatures and the addition of water or other volatiles which lower the solidus temperature (temperature at which partial melting commences) of these rocks. It was long debated whether crustal thickening in orogens (mountain belts along convergent boundaries )

11000-405: The mantle. Although the fractional crystallisation of basaltic melts can yield small amounts of granites, which are sometimes found in island arcs, such granites must occur together with large amounts of basaltic rocks. H-type granites were suggested for hybrid granites, which were hypothesized to form by mixing between mafic and felsic from different sources, such as M-type and S-type. However,

11125-562: The massif lies mostly within France, and is bounded by the valley of the Arve , containing the towns of Argentière , Chamonix 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 . The southern side of

11250-430: The massif were much in demand, as were locally produced goods such as horn trinkets and honey. Granite Granite ( / ˈ ɡ r æ n ɪ t / GRAN -it ) is a coarse-grained ( phaneritic ) intrusive igneous rock composed mostly of quartz , alkali feldspar , and plagioclase . It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies underground. It

11375-418: 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 2,000 to 2,500 m (6,600 to 8,200 ft), summer temperatures can be between 5 and 15 °C (41 and 59 °F), but feeling much colder because of wind chill in windy or wet conditions. Precipitation

11500-403: The massif, from the valley bottoms right up to 3,800 m (12,500 ft) where the alpine chrysanthemum ( Leucanthemopsis alpina  [ fr ] ) 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 3,100 metres (10,200 feet). This was well above

11625-621: The mid-way station of the Skyway Monte Bianco , or on foot from La Palud within two hours and an ascent of 800 m (2,600 ft). The botanical garden derives its name from the genus of mountain flowers, Saussurea (Saw-worts) which itself was named after Horace-Bénédict de Saussure , whose enthusiasm for scientific research in the mountains led to the first ascent of Mont Blanc in 1786. The mountains around Mont Blanc are home to many mammal species, including ibex, chamois , deer, mountain hare and alpine marmot (including

11750-400: 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

11875-425: The modern Tour du Mont Blanc walking trail still follow the route of a Roman road along the Col du Bonhomme and the Col de la Seigne. The Romans occupied Martigny to the north of the massif, and their influence spread out well beyond the Alps into much of northern Europe. As a result of aggressive pressure from tribes in the north, the imperial forces of Rome were gradually withdrawn from the alpine regions until, by

12000-462: 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 −20 °C (−4 °F). The summit is also prone to strong winds and sudden weather changes. Because of

12125-416: The mountains of the Mont Blanc range to the attention of a wide audience for the first time. In 1760, Horace-Bénédict de Saussure offered a large financial prize to the first people who successfully ascended Mont Blanc. The summit was finally attained on 8 August 1786 by two Chamonix men, the guide Jacques Balmat and Dr. Michel Paccard . The decades that followed saw the gradual opening up of Chamonix to

12250-730: The name Alpes Penninae , or Poeninae , to the highest parts of the Alps—which extended from Mont Blanc to Monte Rosa . They took over Aosta from the Salassi Celtic tribe in 25 AD and engineered roads which extended northwards into Europe via the Great St Bernard Pass and the Little St Bernard Pass . Courmayeur, on the southern side of the massif, began to develop as a stop-off along their trans-alpine trading routes between Italy and France. Parts of

12375-419: The need for better environmental protection, including a call for World Heritage Site status. The Mont Blanc massif is 46 kilometres (29 mi) 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 20 km (12 mi) across. The northwestern side of

12500-549: 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

12625-547: 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 3,820 metres (12,533 ft). 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 4,000 metres (13,123 ft) in height, including

12750-609: 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 600 and 1,200 metres (2,000 and 3,900 ft). Daytime valley temperatures in July and August may range up to 25 °C (77 °F), sometimes reaching 30 °C (86 °F). The greatest snowfall occurs between

12875-441: The overlying crust. Early fractional crystallisation serves to reduce a melt in magnesium and chromium, and enrich the melt in iron, sodium, potassium, aluminum, and silicon. Further fractionation reduces the content of iron, calcium, and titanium. This is reflected in the high content of alkali feldspar and quartz in granite. The presence of granitic rock in island arcs shows that fractional crystallization alone can convert

13000-497: The permanent snow line, but on rocks that were so steep that little snow could rest. These arctic-alpine species included: Androsace carnea  [ es ] ; Androsace chamaejasme  [ de ] ; Arabis caerulea  [ de ] ; Cardamine bellidifolia ; Draba hirta ; Saxifraga androsacea  [ es ] and Silene acaulis (occurring down to 1,500 m (4,900 ft)). Between 2,500 and 3,100 m (8,200 and 10,200 ft), Humboldt noted

13125-488: The public in 2006 and tells the story of the early crystal-hunters (known as cristalliers ). Many specimens collected from across the massif are displayed there. 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

13250-736: The reign of Amenemhat III once had a polished granite pyramidion or capstone, which is now on display in the main hall of the Egyptian Museum in Cairo (see Dahshur ). Other uses in Ancient Egypt include columns , door lintels , sills , jambs , and wall and floor veneer. How the Egyptians worked the solid granite is still a matter of debate. Tool marks described by the Egyptologist Anna Serotta indicate

13375-420: The relative percentages of quartz, alkali feldspar, and plagioclase (the QAPF classification ), with true granite representing granitic rocks rich in quartz and alkali feldspar. Most granitic rocks also contain mica or amphibole minerals, though a few (known as leucogranites ) contain almost no dark minerals. Granite is nearly always massive (lacking any internal structures), hard (falling between 6 and 7 on

13500-564: The risk factors in granite country and design rules relating, in particular, to preventing accumulation of radon gas in enclosed basements and dwellings. A study of granite countertops was done (initiated and paid for by the Marble Institute of America) in November 2008 by National Health and Engineering Inc. of USA. In this test, all of the 39 full-size granite slabs that were measured for the study showed radiation levels well below

13625-418: The rock's high quartz content and dearth of available bases, with the base-poor status predisposing the soil to acidification and podzolization in cool humid climates as the weather-resistant quartz yields much sand. Feldspars also weather slowly in cool climes, allowing sand to dominate the fine-earth fraction. In warm humid regions, the weathering of feldspar as described above is accelerated so as to allow

13750-414: The rocks often bear a close resemblance. Under these conditions, granitic melts can be produced in place through the partial melting of metamorphic rocks by extracting melt-mobile elements such as potassium and silicon into the melts but leaving others such as calcium and iron in granulite residues. This may be the origin of migmatites . A migmatite consists of dark, refractory rock (the melanosome ) that

13875-492: The roof of a shallow magma chamber accompanied by a caldera eruption.) There is evidence for cauldron subsidence at the Mt. Ascutney intrusion in eastern Vermont. Evidence for piecemeal stoping is found in intrusions that are rimmed with igneous breccia containing fragments of country rock. Assimilation is another mechanism of ascent, where the granite melts its way up into the crust and removes overlying material in this way. This

14000-616: 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, 15   million years ago. Finally, came the Quaternary era, when successive ice ages saw vast glaciers advance, retreat, and then advance again. Their movement across

14125-436: 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. The Mont Blanc massif consists predominantly of ancient granite rocks. The Alps have their origins 770   million years ago when upheaval of

14250-512: The slopes below les Courtes had yielded many large specimens. He recounted that in 1745 a guide had stated he had collected over 300 pounds (136 kg) 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

14375-589: The summit of Mont Blanc) precipitation is considerably less, with only around 1,100 mm (43 in) recorded, despite the latter measurements being taken at a height of 4,300 metres (14,100 ft). 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 1,000 metres (3,300 ft) receive only around 600 to 700 mm (24 to 28 in) of precipitation per year, which

14500-421: 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. A wide range of glaciers and glacial structures can be found across

14625-435: The surface than magmas of I-type granites, which are thus more common as volcanic rock (rhyolite). They are also orogenic but range from metaluminous to strongly peraluminous. Although both I- and S-type granites are orogenic, I-type granites are more common close to the convergent boundary than S-type. This is attributed to thicker crust further from the boundary, which results in more crustal melting. A-type granites show

14750-502: The uranium washes into the sediments from the granite uplands and associated, often highly radioactive pegmatites. Cellars and basements built into soils over granite can become a trap for radon gas, which is formed by the decay of uranium. Radon gas poses significant health concerns and is the number two cause of lung cancer in the US behind smoking. Thorium occurs in all granites. Conway granite has been noted for its relatively high thorium concentration of 56±6 ppm. There

14875-617: The use of flint tools on finer work with harder stones, e.g. when producing the hieroglyphic inscriptions. Patrick Hunt has postulated that the Egyptians used emery , which has greater hardness. The Seokguram Grotto in Korea is a Buddhist shrine and part of the Bulguksa temple complex. Completed in 774 AD, it is an artificial grotto constructed entirely of granite. The main Buddha of

15000-476: 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

15125-464: The world, as well as the rest of the Mont Blanc massif. The many published accounts of climbs and impressive sights amongst or around the mountain range attracted numerous wealthy and notable visitors, for whom a visit to marvel at the Sea of Ice (the Mer de Glace) became a fashionable thing to experience. In July 1816, Mary Shelley and Percy Bysshe Shelley toured the Alps and visited Chamouni (as it

15250-428: Was inspired by the river Arve, the snow-covered summits, the chaotic glaciers and the forests that he experienced during their visit. Far, far above, piercing the infinite sky, Mont Blanc appears—still, snowy, and serene— Its subject mountains their unearthly forms Pile around it, ice and rock; broad vales between Of frozen floods, unfathomable deeps, Blue as the overhanging heaven, that spread And wind among

15375-405: Was sufficient to produce granite melts by radiogenic heating , but recent work suggests that this is not a viable mechanism. In-situ granitization requires heating by the asthenospheric mantle or by underplating with mantle-derived magmas. Granite magmas have a density of 2.4 Mg/m , much less than the 2.8 Mg/m of high-grade metamorphic rock. This gives them tremendous buoyancy, so that ascent of

15500-564: Was supposed to occur across a migrating front. However, experimental work had established by the 1960s that granites were of igneous origin. The mineralogical and chemical features of granite can be explained only by crystal-liquid phase relations, showing that there must have been at least enough melting to mobilize the magma. However, at sufficiently deep crustal levels, the distinction between metamorphism and crustal melting itself becomes vague. Conditions for crystallization of liquid magma are close enough to those of high-grade metamorphism that

15625-544: Was then known), as well as the Mer de Glace and the Bossons Glacier. They jointly published their accounts and letters in a work entitled: History of a Six Weeks' Tour through a part of France, Switzerland, Germany, and Holland; with Letters Descriptive of a Sail Round the Lake of Geneva and of the Glaciers of Chamouni . The book concludes with Mont Blanc , a 144-line poem by Percy Shelley, written whilst in Chamonix and which

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