The Alps are the highest and most extensive mountain range system that lies in Europe, separating Southern from Central and Western Europe and stretching 1,200 kilometres across eight Alpine countries: France, Italy, Liechtenstein, Austria and Slovenia. 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, at 4,810 m is the highest mountain in the Alps; the Alpine region area contains about a hundred peaks higher than 4,000 metres. The altitude and size of the range affects the climate in Europe. Wildlife such as ibex live in the higher peaks to elevations of 3,400 m, plants such as Edelweiss grow in rocky areas in lower elevations as well as in higher elevations. Evidence of human habitation in the Alps goes back to the Palaeolithic era.
A mummified man, determined to be 5,000 years old, was discovered on a glacier at the Austrian–Italian border in 1991. By the 6th century BC, the Celtic La Tène culture was well established. Hannibal famously crossed the Alps with a herd of elephants, the Romans had settlements in the region. In 1800, Napoleon crossed one of the mountain passes with an army of 40,000; the 18th and 19th centuries saw an influx of naturalists and artists, in particular, the Romantics, followed by the golden age of alpinism as mountaineers began to ascend the peaks. The Alpine region has a strong cultural identity; the traditional culture of farming and woodworking still exists in Alpine villages, although the tourist industry began to grow early in the 20th century and expanded after World War II to become the dominant industry by the end of the century. The Winter Olympic Games have been hosted in the Swiss, Italian and German Alps. At present, the region has 120 million annual visitors; the English word Alps derives from the Latin Alpes.
Maurus Servius Honoratus, an ancient commentator of Virgil, says in his commentary that all high mountains are called Alpes by Celts. The term may be common to Italo-Celtic, because the Celtic languages have terms for high mountains derived from alp; this may be consistent with the theory. According to the Oxford English Dictionary, the Latin Alpes might derive from a pre-Indo-European word *alb "hill". Albania, a name not native to the region known as the country of Albania, has been used as a name for a number of mountainous areas across Europe. In Roman times, "Albania" was a name for the eastern Caucasus, while in the English languages "Albania" was used as a name for Scotland, although it is more derived from the Latin albus, the color white; the Latin word Alpes could come from the adjective albus. In modern languages the term alp, albe or alpe refers to a grazing pastures in the alpine regions below the glaciers, not the peaks. An alp refers to a high mountain pasture where cows are taken to be grazed during the summer months and where hay barns can be found, the term "the Alps", referring to the mountains, is a misnomer.
The term for the mountain peaks varies by nation and language: words such as Horn, Kopf, Spitze and Berg are used in German speaking regions. The Alps are a crescent shaped geographic feature of central Europe that ranges in a 800 km arc from east to west and is 200 km in width; the mean height of the mountain peaks is 2.5 km. The range stretches from the Mediterranean Sea north above the Po basin, extending through France from Grenoble, stretching eastward through mid and southern Switzerland; the range continues onward toward Vienna and east to the Adriatic Sea and Slovenia. To the south it dips into northern Italy and to the north extends to the southern border of Bavaria in Germany. In areas like Chiasso and Allgäu, the demarcation between the mountain range and the flatlands are clear; the countries with the greatest alpine territory are Austria, Italy and Switzerland. The highest portion of the range is divided by the glacial trough of the Rhône valley, from Mont Blanc to the Matterhorn and Monte Rosa on the southern side, the Bernese Alps on the northern.
The peaks in the easterly portion of the range, in Austria and Slovenia, are smaller than those in the central and western portions. The variances in nomenclature in the region spanned by the Alps makes classification of the mountains and subregions difficult, but a general classification is that of the Eastern Alps and Western Alps with the divide between the two occurring in eastern Switzerland according to geologist Stefan Schmid, near the Splügen Pass; the highest peaks of the Western Alps and Eastern Alps are Mont Blanc, at 4,810 m and Piz Bernina at 4,049 metres. The second-highest major
Mass wasting known as slope movement or mass movement, is the geomorphic process by which soil, sand and rock move downslope as a solid, continuous or discontinuous mass under the force of gravity, but with characteristics of a flow as in debris flows and mudflows. Types of mass wasting include creep, flows and falls, each with its own characteristic features, taking place over timescales from seconds to hundreds of years. Mass wasting occurs on both terrestrial and submarine slopes, has been observed on Earth, Mars and Jupiter's moon Io; when the gravitational force acting on a slope exceeds its resisting force, slope failure occurs. The slope material's strength and cohesion and the amount of internal friction between material help maintain the slope's stability and are known collectively as the slope's shear strength; the steepest angle that a cohesionless slope can maintain without losing its stability is known as its angle of repose. When a slope made of loose material possesses this angle, its shear strength counterbalances the force of gravity acting upon it.
Mass wasting may occur at a slow rate in areas that are dry or those areas that receive sufficient rainfall such that vegetation has stabilized the surface. It may occur at high speed, such as in rockslides or landslides, with disastrous consequences, both immediate and delayed, e.g. resulting from the formation of landslide dams. Factors that change the potential of mass wasting include: change in slope angle, weakening of material by weathering, increased water content. Volcano flanks can become over-steep resulting in mass wasting; this is now a recognised part of the growth of all active volcanoes. It is seen on submarine as well as surface volcanoes: Loihi in the Hawaiian volcanic chain and Kick'em Jenny in the Caribbean volcanic arc are two submarine volcanoes that are known to undergo mass wasting; the failure of the northern flank of Mount St Helens in 1980 showed how volcanic flanks can deform and fail. Water can decrease the stability of a slope depending on the amount present. Small amounts of water can strengthen soils because the surface tension of water increases soil cohesion.
This allows the soil to resist erosion better than. If too much water is present the water may act to increase the pore pressure, reducing friction, accelerating the erosion process and resulting in different types of mass wasting. A good example of this is to think of a sand castle. Water must be mixed with sand in order for the castle to keep its shape. If too much water is added the sand washes away, if not enough water is added the sand falls and cannot keep its shape. Water increases the mass of the soil, this is important because an increase in mass means that there will be an increase in velocity if mass wasting is triggered. Saturated water, eases the process of mass wasting in that the rock and soil debris are washed down-slope. Based on how the soil, regolith or rock moves downslope as a whole, mass movements can be broadly classified as creeps and landslides. Soil creep is a long term mass movement; the combination of small movements of soil or rock in different directions over time are directed by gravity downslope.
The steeper the slope, the faster the creep. The creep makes trees and shrubs curve to maintain their perpendicularity, they can trigger landslides if they lose their root footing; the surface soil can migrate under the influence of cycles of freezing and thawing, or hot and cold temperatures, inching its way towards the bottom of the slope forming terracettes. Landslides are preceded by soil creep accompanied with soil sloughing — loose soil that falls and accumulates at the base of the steepest creep sections. A landslide called a landslip, is a slow or rapid movement of a large mass of earth and rocks down a hill or a mountainside. Little or no flowage of the materials occurs on a given slope until heavy rain and resultant lubrication by the same rainwater facilitate the movement of the materials, causing a landslide to occur. In particular, if the main feature of the movement is a slide along a planar or curved surface, the landslide is termed slump, earth slide, debris slide or rock slide, depending on the prevailing material.
Movement of soil and regolith that more resembles fluid behavior is called a flow. These include avalanches, debris flows, earth flow and sturzstroms. Water and ice are involved in enabling fluid-like motion of the material. A fall, including rockfall and debris fall, occurs where regolith cascades down a slope, but is not of sufficient volume or viscosity to behave as a flow. Falls are promoted in rocks. Falls can result from undercutting by running water as well as by waves, they occur at steep slopes such as a cliff face. The rock material may be loosened by earthquakes, plant-root wedging, expanding ice, among other things; the accumulation of rock material that has fallen and resides at the base of the structure is known as talus. Soil and regolith remain on a hillslope only while the gravitational forces are unable to overcome the frictional forces keeping the material in place; some factors that reduce the frictional resistance relative to the downslope forces, thus can trigger slope movement, can include: earthquakes increased overburden from structures increased soil moisture reduction of roots holding the soil to bedrock undercutting of the slope by excavation or erosion weathering by frost heave or chem
A river is a natural flowing watercourse freshwater, flowing towards an ocean, lake or another river. In some cases a river flows into the ground and becomes dry at the end of its course without reaching another body of water. Small rivers can be referred to using names such as stream, brook and rill. There are no official definitions for the generic term river as applied to geographic features, although in some countries or communities a stream is defined by its size. Many names for small rivers are specific to geographic location. Sometimes a river is defined as being larger than a creek, but not always: the language is vague. Rivers are part of the hydrological cycle. Potamology is the scientific study of rivers, while limnology is the study of inland waters in general. Most of the major cities of the world are situated on the banks of rivers, as they are, or were, used as a source of water, for obtaining food, for transport, as borders, as a defensive measure, as a source of hydropower to drive machinery, for bathing, as a means of disposing of waste.
A river begins at a source, follows a path called a course, ends at a mouth or mouths. The water in a river is confined to a channel, made up of a stream bed between banks. In larger rivers there is also a wider floodplain shaped by flood-waters over-topping the channel. Floodplains may be wide in relation to the size of the river channel; this distinction between river channel and floodplain can be blurred in urban areas where the floodplain of a river channel can become developed by housing and industry. Rivers can flow down mountains, through valleys or along plains, can create canyons or gorges; the term upriver refers to the direction towards the source of the river, i.e. against the direction of flow. The term downriver describes the direction towards the mouth of the river, in which the current flows; the term left bank refers to the left bank in the direction of right bank to the right. The river channel contains a single stream of water, but some rivers flow as several interconnecting streams of water, producing a braided river.
Extensive braided rivers are now found in only a few regions worldwide, such as the South Island of New Zealand. They occur on peneplains and some of the larger river deltas. Anastamosing rivers are quite rare, they have multiple sinuous channels carrying large volumes of sediment. There are rare cases of river bifurcation in which a river divides and the resultant flows ending in different seas. An example is the bifurcation of Nerodime River in Kosovo. A river flowing in its channel is a source of energy which acts on the river channel to change its shape and form. In 1757, the German hydrologist Albert Brahms empirically observed that the submerged weight of objects that may be carried away by a river is proportional to the sixth power of the river flow speed; this formulation is sometimes called Airy's law. Thus, if the speed of flow is doubled, the flow would dislodge objects with 64 times as much submerged weight. In mountainous torrential zones this can be seen as erosion channels through hard rocks and the creation of sands and gravels from the destruction of larger rocks.
A river valley, created from a U-shaped glaciated valley, can easily be identified by the V-shaped channel that it has carved. In the middle reaches where a river flows over flatter land, meanders may form through erosion of the river banks and deposition on the inside of bends. Sometimes the river will cut off a loop, shortening the channel and forming an oxbow lake or billabong. Rivers that carry large amounts of sediment may develop conspicuous deltas at their mouths. Rivers whose mouths are in saline tidal waters may form estuaries. Throughout the course of the river, the total volume of water transported downstream will be a combination of the free water flow together with a substantial volume flowing through sub-surface rocks and gravels that underlie the river and its floodplain. For many rivers in large valleys, this unseen component of flow may exceed the visible flow. Most but not all rivers flow on the surface. Subterranean rivers flow underground in caverns; such rivers are found in regions with limestone geologic formations.
Subglacial streams are the braided rivers that flow at the beds of glaciers and ice sheets, permitting meltwater to be discharged at the front of the glacier. Because of the gradient in pressure due to the overlying weight of the glacier, such streams can flow uphill. An intermittent river only flows and can be dry for several years at a time; these rivers are found in regions with limited or variable rainfall, or can occur because of geologic conditions such as a permeable river bed. Some ephemeral rivers flow during the summer months but not in the winter; such rivers are fed from chalk aquifers which recharge from winter rainfall. In England these rivers are called bournes and give their name to places such as Bournemouth and Eastbourne. In humid regions, the location where flow begins in the smallest tributary streams moves upstream in response to precipitation and downstream in its absence or when active summer vegetation diverts water for evapotrans
Helvellyn is a mountain in the English Lake District, the highest point of the Helvellyn range, a north-south line of mountains to the north of Ambleside, between the lakes of Thirlmere and Ullswater. Helvellyn is the third-highest point both in England and in the Lake District, access to Helvellyn is easier than to the two higher peaks of Scafell Pike and Sca Fell; the scenery includes two sharp-topped ridges on the eastern side. The volcanic rocks of which the mountain is made were formed in the caldera of an ancient volcano, many of them in violently explosive eruptions, about 450 million years ago during the Ordovician period. During the last ice age these rocks were carved by glaciers to create the landforms seen today. Since the end of the last ice age, small populations of arctic-alpine plants have survived in favourable spots on rock ledges high in the eastern coves. Rare to Britain species of alpine butterfly, the mountain ringlet live on and around Helvellyn. Mineral veins, some with deposits of the lead ore galena, do exist within Helvellyn's rocks, but attempts to find sufficient quantities of lead to be worth mining have not been successful.
Tourism has been a more successful industry in the area. For over two hundred years visitors have been drawn by the lake and mountain scenery of the Lake District, many have made their way to the top of Helvellyn. Among the early visitors to Helvellyn were the poets Samuel Taylor Coleridge and William Wordsworth, both of whom lived nearby at one period. Many routes up the mountain are possible so; the view from the top is one of the most extensive over the Lake District, on a clear day the view can stretch from Scotland to Wales. However, traversing the mountain is not without dangers; the artist Charles Gough is more famous for his death on Striding Edge in 1805 than for what he achieved in his life. Among many human feats upon the mountain, one of the strangest was the landing and take-off of a small aeroplane on the summit in 1926. In January 2018 Helvellyn was named'Britain's Best Walk'in an ITV show presented by Julia Bradbury. Since early 2018 the summit of Helvellyn including both Striding and Swirral Edges and the wider Glenridding Common are now managed by the John Muir Trust, a wild places conservation charity under a three year lease with the Lake District Park Authority.
The top of Helvellyn is a broad plateau, trending from north-west to south-east for about a kilometre between Lower Man and the start of Striding Edge. Throughout this distance it remains more than 900 m high. To the west the ground drops at first but more steeply down to Thirlmere, while on the eastern side three deep glacial coves, each backed by high cliffs, are separated by two spectacular sharp ridges or arêtes; the middle of these coves contains Red Tarn. Like much of the main ridge of the range, Helvellyn stands on the watershed between Thirlmere and the Derwent river system to the west, Ullswater and the Eden river system to the east. Streams on the west side drain directly into Thirlmere, apart from Helvellyn Gill which flows into a parallel valley to the east of Great How and empties into St John's Beck. However, when Thirlmere reservoir was built, a leat was constructed to capture the water of Helvellyn Gill, so that it is now directed into the reservoir. A never-failing spring called Brownrigg Well exists 90 m below the summit of Helvellyn, about 500 m due west of the highest point, at the head of Whelpside Gill.
In the nineteenth century a leat was constructed to direct the water of this spring into the gill to its north to serve the needs of the Helvellyn Mine further down. This leat has now fallen into disuse; the gill it led to is not named on any map. Whelp Side, between Whelpside Gill and Mines Gill, appears as a distinct shoulder of the mountain when seen from the west grassy though with a few crags and boulders in places, with coniferous plantations on its lower slopes which were planted to stabilise the land around the reservoir. North of Mines Gill are the Helvellyn Screes, a more craggy stretch of hillside, beneath the north-west ridge, with a loose scree covering in places; the deep coves on the rocky eastern side of Helvellyn drain into Ullswater. Water from Brown Cove and Red Tarn unite below Catstye Cam to form Glenridding Beck, which flows through Glenridding village to the lake, while Nethermost Cove drains into the same lake via Grisedale Beck and Patterdale village. Red Tarn, enclosed between Striding Edge and Swirral Edge, is about 25 m deep, but in the mid-nineteenth century a dam was built to increase its capacity and supply the needs of the Greenside Mine near Glenridding.
That dam has now gone and the tarn has returned to its natural size. It contains brown trout and schelly, a species of whitefish found in only four bodies of water in the Lake District. A second reservoir was built around 1860 in Brown Cove, between Swirral Edge and Lower Man, along with one further down the valley in Keppel Cove; these provided water to generate hydroelectric power for the lead mine. The dam in Keppel Cove is still in place; the remains of the dam in Brown Cove can be seen, but again water leaks through it. It is unclear whether there was a natural tarn in Brown Cove. Guidebook writers before 1860 refer only to Keppel Cove Tarn to the north of Swirral Edge. A total of five ridges diverge from the summit ridge of Helvellyn at different points; the north-west ridge continues from Lower Man over Browncove Crags, becoming almost
A pyramidal peak, sometimes called a glacial horn in extreme cases, is an angular pointed mountain peak which results from the cirque erosion due to multiple glaciers diverging from a central point. Pyramidal peaks are examples of nunataks. Glaciers forming in drainages on the sides of a mountain, develop bowl-shaped basins called cirques. Cirque glaciers have rotational sliding that abrades the floor of the basin more than walls and that causes the bowl shape to form; as cirques are formed by glaciation in an alpine environment, the headwall and ridges between parallel glaciers called arêtes become more steep and defined. This occurs due to mass wasting beneath the ice surface, it is held that a common cause for headwall steepening and extension headward is the crevasses known as bergschrund that occur between the moving ice and the headwall. Plucking and shattering can be seen here by those exploring the crevasses. A cirque is exposed; when three or more of these cirques converge on a central point, they create a pyramid-shaped peak with steep walls.
These horns are a common shape for mountain tops in glaciated areas. The number of faces of a horn depends on the number of cirques involved in the formation of the peak: three to four is most common. Horns with more than four faces include the Mönch. A peak with four symmetrical faces is called a Matterhorn; the peak of a glacial horn will outlast the arêtes on its flanks. As the rock around it erodes, the horn gains in prominence. A glacial horn will have near vertical faces on all sides. In the Alps, "horn" is the name of exposed peaks with slope inclinations of 45-60°. Artesonraju in Áncash, Peru Cradle Mountain in Tasmania, Australia Crowsnest Mountain in Alberta, Canada Fitz Roy in Patagonia, South America Grand Teton in Grand Teton National Park, United States K2 in China and Pakistan Kamenitsa, Pirin Mountain, Bulgaria Ketil in Greenland Kinnerly Peak in Glacier National Park, United States The Kitzsteinhorn in Salzburg, Austria The Matterhorn in Italy and Switzerland Momin Dvor, Pirin Mountain, Bulgaria Mount Aspiring/Tititea in Otago, New Zealand Mount Assiniboine in British Columbia, Canada Mount Thielsen in Oregon, United States Mount Wilbur in Glacier National Park, United States Nevado Las Agujas in Los Ríos, Chile Pilot Peak in Wyoming, United States Puy Mary in Cantal, France The Pyramid in Antarctica Pyramiden in Greenland Reynolds Mountain in Glacier National Park, United States Shivling in Uttarakhand, India Stob Dearg in Glen Coe, Scotland Store Skagastølstind in Sogn og Fjordane, Norway Vihren, Pirin Mountain, Bulgaria Glacial landforms Easterbrook, Don J..
Surface Landforms. Upper Saddle River, NJ: Prentice Hall. Pp. 334–336. ISBN 978-0138609580. Lemke, Karen A.. "Illustrated Glossary of Alpine Glacial Landforms". Archived from the original on August 13, 2012. Retrieved October 12, 2012
Ice is water frozen into a solid state. Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaque bluish-white color. In the Solar System, ice is abundant and occurs from as close to the Sun as Mercury to as far away as the Oort cloud objects. Beyond the Solar System, it occurs as interstellar ice, it is abundant on Earth's surface – in the polar regions and above the snow line – and, as a common form of precipitation and deposition, plays a key role in Earth's water cycle and climate. It occurs as frost, icicles or ice spikes. Ice molecules can exhibit more different phases that depend on temperature and pressure; when water is cooled up to three different types of amorphous ice can form depending on the history of its pressure and temperature. When cooled correlated proton tunneling occurs below −253.15 °C giving rise to macroscopic quantum phenomena. All the ice on Earth's surface and in its atmosphere is of a hexagonal crystalline structure denoted as ice Ih with minute traces of cubic ice denoted as ice Ic.
The most common phase transition to ice Ih occurs when liquid water is cooled below 0 °C at standard atmospheric pressure. It may be deposited directly by water vapor, as happens in the formation of frost; the transition from ice to water is melting and from ice directly to water vapor is sublimation. Ice is used in a variety including cooling, winter sports and ice sculpture; as a occurring crystalline inorganic solid with an ordered structure, ice is considered to be a mineral. It possesses a regular crystalline structure based on the molecule of water, which consists of a single oxygen atom covalently bonded to two hydrogen atoms, or H–O–H. However, many of the physical properties of water and ice are controlled by the formation of hydrogen bonds between adjacent oxygen and hydrogen atoms. An unusual property of ice frozen at atmospheric pressure is that the solid is 8.3% less dense than liquid water. The density of ice is 0.9167–0.9168 g/cm3 at 0 °C and standard atmospheric pressure, whereas water has a density of 0.9998–0.999863 g/cm3 at the same temperature and pressure.
Liquid water is densest 1.00 g/cm3, at 4 °C and becomes less dense as the water molecules begin to form the hexagonal crystals of ice as the freezing point is reached. This is due to hydrogen bonding dominating the intermolecular forces, which results in a packing of molecules less compact in the solid. Density of ice increases with decreasing temperature and has a value of 0.9340 g/cm3 at −180 °C. When water freezes, it increases in volume; the effect of expansion during freezing can be dramatic, ice expansion is a basic cause of freeze-thaw weathering of rock in nature and damage to building foundations and roadways from frost heaving. It is a common cause of the flooding of houses when water pipes burst due to the pressure of expanding water when it freezes; the result of this process is that ice floats on liquid water, an important feature in Earth's biosphere. It has been argued that without this property, natural bodies of water would freeze, in some cases permanently, from the bottom up, resulting in a loss of bottom-dependent animal and plant life in fresh and sea water.
Sufficiently thin ice sheets allow light to pass through while protecting the underside from short-term weather extremes such as wind chill. This creates a sheltered environment for algal colonies; when sea water freezes, the ice is riddled with brine-filled channels which sustain sympagic organisms such as bacteria, algae and annelids, which in turn provide food for animals such as krill and specialised fish like the bald notothen, fed upon in turn by larger animals such as emperor penguins and minke whales. When ice melts, it absorbs as much energy as it would take to heat an equivalent mass of water by 80 °C. During the melting process, the temperature remains constant at 0 °C. While melting, any energy added breaks the hydrogen bonds between ice molecules. Energy becomes available to increase the thermal energy only after enough hydrogen bonds are broken that the ice can be considered liquid water; the amount of energy consumed in breaking hydrogen bonds in the transition from ice to water is known as the heat of fusion.
As with water, ice absorbs light at the red end of the spectrum preferentially as the result of an overtone of an oxygen–hydrogen bond stretch. Compared with water, this absorption is shifted toward lower energies. Thus, ice appears blue, with a greener tint than liquid water. Since absorption is cumulative, the color effect intensifies with increasing thickness or if internal reflections cause the light to take a longer path through the ice. Other colors can appear in the presence of light absorbing impurities, where the impurity is dictating the color rather than the ice itself. For instance, icebergs containing impurities can appear grey or green. Ice may be any one of the 18 known solid crystalline phases of water, or in an amorphous solid state at various densities. Most liquids under increased pressure freeze at higher temperatures because the pressure helps to hold the molecules together. However, the strong hydrogen bonds in water make it different: For some pressures higher than 1 atm, water freezes at a temperature below
Half Dome is a granite dome at the eastern end of Yosemite Valley in Yosemite National Park, California. It is a well-known rock formation in the park, named for its distinct shape. One side is a sheer face while the other three sides are smooth and round, making it appear like a dome cut in half; the granite crest rises more than 4,737 ft above the valley floor. The impression from the valley floor that this is a round dome that has lost its northwest half is an illusion. From Washburn Point, Half Dome can be seen as a thin ridge of rock, an arête, oriented northeast-southwest, with its southeast side as steep as its northwest side except for the top. Although the trend of this ridge, as well as that of Tenaya Canyon, is controlled by master joints, 80 percent of the northwest "half" of the original dome may well still be there; as late as the 1870s, Half Dome was described as "perfectly inaccessible" by Josiah Whitney of the California Geological Survey. The summit was reached by George G. Anderson in October 1875, via a route constructed by drilling and placing iron eyebolts into the smooth granite.
Today, Half Dome may now be ascended in several different ways. Thousands of hikers reach the top each year by following an 8.5 mi trail from the valley floor. After a rigorous 2 mi approach, including several hundred feet of granite stairs, the final pitch up the peak's steep but somewhat rounded east face is ascended with the aid of a pair of post-mounted braided steel cables constructed close to the Anderson route in 1919. Alternatively, over a dozen rock climbing routes lead from the valley up Half Dome's vertical northwest face; the first technical ascent was in 1957 via a route pioneered by Royal Robbins, Mike Sherrick, Jerry Gallwas, today known as the Regular Northwest Face. Their five-day epic was the first Grade VI climb in the United States, their route has now been free. Other technical routes ascend the west shoulder; the Half Dome Cable Route hike runs from the valley floor to the top of the dome in 8.2 mi, with 4,800 ft of elevation gain. The length and difficulty of the trail used to keep it less crowded than other park trails, but in recent years the trail traffic has grown to as many as 800 people a day.
The hike can be done from the valley floor in a single long day, but many people break it up by camping overnight in Little Yosemite Valley. The trail climbs past Vernal and Nevada Falls continues into Little Yosemite Valley north to the base of the northeast ridge of Half Dome itself; the final 400 ft ascent is steeply up the rock between two steel cables used as handholds. The cables are raised onto a series of metal poles in late May; the cables are taken down from the poles for the winter in early October, but they are still fixed to the rock surface and can be used. The National Park Service recommends against climbing the route when the cables are down and when the surface of the rock is wet and slippery; the Cable Route is rated class 3, while the same face away from the cables is rated class 5. The Cable Route can be crowded. In past years, as many as 1,000 hikers per day have sometimes climbed the dome on a summer weekend, about 50,000 hikers climb it every year. Since 2011, all hikers who intend to ascend the Cable Route must now obtain permits before entering the park.
Permits are checked by a ranger on the trail, no hikers without permits are allowed to hike beyond the base of the sub-dome or to the bottom of the cables. Hikers caught bypassing the rangers to visit either the sub-dome or main dome without a permit face fines of up to $5,000 and/or 6 months in jail. Backpackers with an appropriate wilderness permit can receive a Half Dome permit when they pick up their wilderness permit with no additional reservation required. Rock climbers who reach the top of Half Dome without entering the subdome area can descend on the Half Dome Trail without a permit; the top of Half Dome is a flat area where climbers can relax and enjoy their accomplishment. The summit offers views of the surrounding areas, including Little Yosemite Valley and the Valley Floor. A notable location to one side of Half Dome is the "Diving Board", where Ansel Adams took his photograph "Monolith, The Face of Half Dome" on April 10, 1927. Confused with "the Visor," a small overhanging ledge at the summit, the Diving Board is on the shoulder of Half Dome.
From 1919 when the cables were erected through 2011, there have been six fatal falls from the cables. The latest fatality occurred on May 21, 2018. Lightning strikes can be a risk while near the summit. On July 27, 1985, five hikers were struck by lightning; the Cable Route was added to the National Register of Historic Places in 2012. 1875 George G. Anderson via drilled spikes on the east slope. 1946 Salathe Route on southwest face, FA by John Salathe and Anton Nelson 1957 Northwest Face, FA by Royal Robbins, Jerry Gallwas and Mike Sherrick. First Grade VI in North America. 1963 Direct Northwest Face, FA by Royal Robbins and Dick McCracken 1969 Tis-sa-ack, FA by Royal Robbins and Don Peterson. 1973 First "clean ascent" of NW face by Dennis Hennek, Doug Robinson, Galen Rowell, Hennek is on the cover of June 1974 National Geographic leading a nut protected traverse see Super Topo too 1987 The Big Chill, FA by Jim Bridwell, Peter Mayfield, Sean Plunkett and Steve Bosque 1989 Shadows, FA by Jim Bridwell, Charles Row, Cito Kirkpatrick, William Westbay 1997 Blue Shift FA by Jay Smith and Karl McConachie.
1964 Salathe Route, FFA by Fran