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9534_21 | Notable private schools in Mountain View include: Khan Lab School, a laboratory school associated with Khan Academy; Saint Francis High School, a Roman Catholic secondary school; German International School of Silicon Valley (GISSV), a PK-12 German-English bilingual international school; and Yew Chung International School of Silicon Valley, a PK-8 Chinese-English bilingual international school.
Library |
9534_22 | Mountain View has one central public library, the Mountain View Public Library, which has video, music, books, and access to the Internet. The library provides outreach services through the bookmobile and S.O.S. volunteer program to those in Mountain View who are unable to come to the main branch. The building was built in 1997. The second floor of the library has a special collection in a room devoted to the history of Mountain View, which features a portrait of Crisanto Castro, for whom the major downtown thoroughfare is named. Displayed outside the library is a piece of the Berlin Wall, installed in 2013.
Infrastructure
Transportation |
9534_23 | The Downtown Mountain View Station is the transit center for the city, connecting the public commuter rail, light rail, bus, and private shuttle systems. Mountain View is served by the Caltrain commuter rail system, which runs from San Francisco to Gilroy. The two Caltrain stations in the city are Downtown Mountain View Station and San Antonio Station. The city is also served by the Santa Clara Valley Transportation Authority (VTA), which operates various bus lines and the light rail system. There are a total of four stations in the city on the Orange Line VTA light rail line, with Downtown Mountain View Station serving as the northern terminus, while the other three stations are Whisman, Middlefield, and Bayshore/NASA. MVgo is a free shuttle service that runs three routes throughout Mountain View beginning and ending at Downtown Mountain View Station during morning and evening commute hours. Many large local employers (including Google, Microsoft, Apple Inc., and NASA Ames Research |
9534_24 | Center) operate employee shuttles that stop at the Downtown Mountain View Station. There is also a free community shuttle bus that serves 50 stops within Mountain View. |
9534_25 | The nearest major airports are San Jose International Airport (SJC), San Francisco International Airport (SFO), and Oakland International Airport (OAK), in that order. Moffett Federal Airfield is located just north of Mountain View, but it is restricted to government, military, and private use. The nearest general aviation airport is the Palo Alto Airport of Santa Clara County.
Utilities
Power in the city is operated by Pacific Gas and Electric Company.
On August 16, 2006, after over a year of test deployments, Google announced that its implementation of free IEEE 802.11g wireless service for all of the city was fully operational. |
9534_26 | On February 19, 2014, the City of Mountain View and Google announced a new connectivity plan for residents, to replace the existing system. Service will be available along the downtown corridor of Mountain View, primarily on Castro Street. Other areas to be covered include Rengstorff Park, the Mountain View Public Library, Senior, Community, and Teen Centers.
Points of interest
Downtown
Mountain View has a pedestrian-friendly downtown centered on Castro Street. The downtown area consists of the seven blocks of Castro Street from the Downtown Mountain View Station transit center in the north to the intersection with El Camino Real in the south. The transit center links the Caltrain commuter rail and Santa Clara Valley Transportation Authority (VTA) light rail and bus systems. |
9534_27 | Four blocks with a concentration of restaurants, cafes, and shops extend south from the downtown station. The Michelin Guide-starred restaurant Chez TJ is located a block from Castro Street on Villa Street. Tied House, located next door, was one of the first brewpubs in the Bay Area, and was a popular stop in downtown until it closed in 2019.
The core of downtown is the plaza shared by City Hall, the Mountain View Center for the Performing Arts (MVCPA) and the Mountain View Public Library. The plaza is used for many community gatherings and events, and features a collection of public art. Peninsula Youth Theatre and TheatreWorks are among the home companies of the MVCPA. The City Hall and MVCPA complex, designed by William Turnbull of San Francisco, opened in 1991. Behind those buildings is Pioneer Park, formerly the site of Mountain View's first cemetery.
The Mountain View Police Department is located two blocks away from Castro Street on Villa Street. |
9534_28 | Since 1971, the city has held the annual Mountain View Art & Wine Festival on Castro Street by closing down the street to traffic for two days. There is a farmers' market in the Caltrain parking lot every Sunday morning. Every summer, once a month, the city celebrates Thursday Night Live by closing off Castro street to cars and providing live music events and car shows on Castro Street.
The entire length of El Camino in Mountain View is a low-density commercial area.
Parks
The largest park in the city is Shoreline Park, which was built on a landfill and runs along the Bay north of U.S. Route 101. It includes Shoreline Amphitheatre, Shoreline Golf Course, as well as Rengstorff House, which is listed in the National Register of Historic Places. On the north side, facing the Bay, the park includes tidal ponds and mudflats, accessible via pedestrian and bicycle paths. The San Francisco Bay Trail runs along Shoreline Park. |
9534_29 | Stevens Creek runs through Mountain View from the south and empties into the Bay in Shoreline Park. A paved pedestrian and bicycle path, the Stevens Creek Trail, runs alongside the creek for nearly its entire distance in Mountain View. Stevens Creek is home to coyotes, gray foxes, black-tailed deer, butterflies, dragonflies, and 150 species of birds, as well as shorebirds that feed in the mudflat. The shorebirds can be seen at low tide.
Other parks include:
Eagle Park, which holds a public swimming pool, dog-friendly lawn, and World War II war memorial
Cuesta Park, a sprawling park with tennis courts, barbecue areas, and playgrounds, near El Camino Hospital and the YMCA
Rengstorff Park, home to a public swimming pool, community center, skate park, fenced dog park, and multiple playgrounds and picnic areas
Charleston Park, a five-acre park located near the Googleplex. The park was designed by SWA Group who received an ASLA Centennial Medallion in 1999 for their work.
Other |
9534_30 | The Computer History Museum is home to the largest and most significant collection of computing artifacts in the world.
The Shoreline Amphitheater is a large outdoor venue for large concerts and shows.
Moffett Field is a joint civil-military federal airfield located between northern Mountain View and northern Sunnyvale, California. It is home to the Air National Guard. Its hangars for blimps and rigid airships (now mostly vacant) make unique landmarks for motorists on Highway 101.
NASA Ames Research Center is a research facility adjacent to Moffett, and also houses a gift-shop NASA visitor center.
The Historic Adobe Building, a small events center on Moffett Boulevard, is listed in the National Register of Historic Places.
St. Joseph Parish was founded in 1905, and survived the 1906 San Francisco earthquake, only to burn down in 1928. St. Joseph's Seminary operated here between 1924 and 1991. The current St. Joseph church building was built in 1929. |
9534_31 | The Mountain View Voice is the local newspaper, which began publishing in 1993.
Sister cities
The Mountain View Sister City Affiliation was incorporated in 1974 as an independent non-profit governed by a Board of Directors. Mountain View is affiliated with the cities of
Iwata, Shizuoka, Japan
Hasselt, Belgium
The rock garden in Pioneer Park was a gift from the sister city of Iwata to celebrate the completion of Mountain View's City Hall building.
See also
Timeline of Mountain View, California
St. Joseph's Seminary (Mountain View, California)
Notable people |
9534_32 | Tully Banta-Cain, two-time Super Bowl champion
Carroll Clark, seven-time Academy Award for Best Art Direction nominee
Laura Chavez, blues, soul, and rhythm and blues guitarist, songwriter and record producer
Assaf Cohen, supporting actor, Heroes and Entourage
Brandon Crawford, professional baseball player in MLB, plays for the San Francisco Giants
Paula Creamer, professional golfer and formerly Women's World Golf Rankings number two player
Hugh Fate, dentist and Alaska state representative
Dave Finocchio, co-founder of Bleacher Report
Doris Gates, author and librarian
Dan Green, powerlifter, world record holder in 220 and 242 lbs weight classes
Steve Jobs, technology entrepreneur, co-founder and CEO of Apple, lived in Mountain View during his childhood
Edward Michael Keating (1925–2003), American publisher, journalist, lawyer; founder of Ramparts, member of the New Left movement.
Salman Khan, Khan Academy online educator, resides in Mountain View |
9534_33 | Mark Keil, five-time ATP tennis doubles champion
Jan Koum, CEO and co-founder of WhatsApp, grew up in Mountain View
Kurt Kuenne, filmmaker and composer best known for the documentary Dear Zachary: A Letter to a Son About His Father
Mark Leonard, former left fielder for the San Francisco Giants and Baltimore Orioles
Sally J. Lieber, former mayor of Mountain View and politician
Kenny Roberts Jr., 2000 500cc Road Racing World Champion
Bianca Sierra, player for Mexico women's national football team.
Jose Antonio Vargas, journalist, filmmaker, immigration rights activist, and namesake of new Mountain View elementary school
Andy Weir, wrote The Martian book and eventual film, while living in Mountain View |
9534_34 | References
Bibliography
External links
1902 establishments in California
Butterfield Overland Mail in California
Cities in Santa Clara County, California
Cities in the San Francisco Bay Area
Incorporated cities and towns in California
Populated places established in 1902
Silicon Valley
Populated coastal places in California |
9535_0 | Upnor Castle is an Elizabethan artillery fort located on the west bank of the River Medway in Kent. It is in the village of Upnor, opposite and a short distance downriver from the Chatham Dockyard, at one time a key naval facility. The fort was intended to protect both the dockyard and ships of the Royal Navy anchored in the Medway. It was constructed between 1559–67 on the orders of Elizabeth I, during a period of tension with Spain and other European powers. The castle consists of a two-storeyed main building protected by a curtain wall and towers, with a triangular gun platform projecting into the river. It was garrisoned by about 80 men with a peak armament of around 20 cannon of various calibres. |
9535_1 | Despite its strategic importance, the castle and the defences of the Thames and Medway were badly neglected during the 17th century. The Dutch Republic mounted an unexpected naval raid in June 1667, and the Dutch fleet was able to breach the defences, capturing two warships and burning others at anchor in the river at Chatham, in one of the worst defeats suffered by the Royal Navy. Upnor Castle acquitted itself better than many of the other defensive sites along the upper Medway, despite its lack of provisioning. Gun fire from the fort and from adjoining emplacements forced a Dutch retreat after a couple of days, before they were able to burn the dockyard itself. |
9535_2 | The raid exposed the weaknesses of the Medway defences and led to the castle losing its role as an artillery fortification. New and stronger forts were built further downriver over the following two centuries, culminating in the construction of massive casemated forts such as Garrison Point Fort, Hoo, and Darnet Forts. Upnor Castle became a naval ammunition depot, storing great quantities of gunpowder, ammunition, and cannon to replenish the warships that came to Chatham for repair and resupply. It remained in military use until as late as 1945. The castle was subsequently opened to the public and is now an English Heritage property.
History
Strategic context |
9535_3 | The River Medway is a major tributary of the Thames, merging at an estuary about east of London. Its upper reaches from Rochester to the confluence with the Thames at Sheerness meander between sand and mud banks for about . The water flows slowly without strong currents and is free of rocks, while the surrounding hills provide shelter from the south-west wind. These characteristics made the section of the river below Rochester Bridge a desirable anchorage for large ships, as they could be anchored safely and grounded for repairs. The complexity of the channel's navigation also provided it with defensive advantages. |
9535_4 | During Henry VIII's reign, the upper Medway gradually became the principal anchorage for ships of the Royal Navy while they were "in ordinary," or out of commission. They were usually stripped of their sails and rigging while in this state and the opportunity was taken to refit and repair them. Storehouses and servicing facilities were built in the Medway towns of Gillingham and Chatham which eventually became the nucleus of the Chatham Dockyard. By the time Elizabeth I came to the throne in 1558, most of the royal fleet used this section of the Medway, known as Chatham and Gillingham Reaches, as an anchorage. |
9535_5 | Although the Thames had been defended from naval attack since Henry VIII's time, when five blockhouses were built as part of the Device Forts chain of coastal defences, there were no equivalents on the Medway. Two medieval castles – Rochester Castle and Queenborough Castle – existed along the river's south bank, but both were intended to defend landward approaches and were of little use for defence. There was thus a pressing need for proper defences to protect the vulnerable ships and shore facilities on the upper Medway. |
9535_6 | Construction
Upnor Castle was commissioned in 1559 by order of Queen Elizabeth and her Privy Council. Six "indifferent persons" chose a site opposite St Mary's Creek in Chatham, on of land belonging to a Thomas Devinisshe of Frindsbury. It was acquired by the Crown – possibly compulsorily purchased – for the sum of £25. Military engineer Sir Richard Lee was given the task of designing the new fortification, but he appears to have been fully occupied with working on the defences of Berwick-upon-Tweed, and the project was carried out by others to his designs. His deputy Humphrey Locke took the role of overseer, surveyor, and chief carpenter, while Richard Watts, the former Rochester mayor and victualler to the navy, managed the project on a day-to-day basis and handled the accounting. |
9535_7 | The castle's original appearance differed significantly from that of today. The arrow-shaped Water Bastion facing into the Medway and the main block behind it were part of the original design. There were also towers at either end of the water frontage, though these were subsequently replaced by towers of a different design. The gatehouse and moat were later additions. A number of derelict buildings in Rochester Castle, Aylesford, and Bopley were pulled down to provide stone for the castle. The main structure had been completed by 1564, but it took another three years and an infusion of extra funds to finish the project. The total cost came to £4,349.
Improvements and repairs |
9535_8 | During the late 16th century, tensions grew between Protestant England and Catholic Spain, leading ultimately to the undeclared Anglo-Spanish War of 1585–1604. Spain was in a strong position to attack the south of England from its possessions in the Spanish Netherlands. New fortifications were erected along the Medway, including a chain stretched across the width of the river below Upnor Castle. The castle itself was poorly manned until Lord High Admiral Charles Howard, 1st Earl of Nottingham highlighted this and recommended that the garrison should be increased. By 1596, it was garrisoned by eighty men who were each paid eight pence per day (equivalent to £6 today). |
9535_9 | Continued fears of a Spanish incursion led to the castle's defences being strengthened between 1599–1601 at the instigation of Sir John Leveson. An arrowhead-shaped timber palisade was erected in front of the Water Bastion to block any attempted landings there. An enclosing ditch some deep and wide was dug around the castle. Flanking turrets were constructed to protect the bastion on the site of the present north and south towers. The bastion itself was raised and a high parapet was added to its edge. A gatehouse and drawbridge were also built to protect the castle's landward side. |
9535_10 | A survey conducted in 1603 recorded that Upnor Castle had 20 guns of various calibres, plus another 11 guns split between two sconces or outworks, known as Bay and Warham Sconces. The castle's armament consisted of a demi-cannon, 7 culverin, 5 demi-culverin, a minion, a falconet, a saker, and four fowlers with two chambers each. Bay Sconce was armed with 4 demi-culverin, while Warham Sconce had 2 culverin and 5 demi-culverin. Eighteen guns were recorded as being mounted in the castle twenty years later. The garrison's armament included 34 longbows, an indication that archery was still of military value even at this late date. By this time, however, the castle was in a state of disrepair. The drawbridge and its raising mechanism were broken, the gun platforms needed repairs, and the courtyard wall had collapsed. A new curtain wall had to be built to protect the landward side of the castle. The foundations of Warham Sconce were reported to have been washed away by the tide, and it |
9535_11 | appears that both sconces were allowed to fall into ruin. |
9535_12 | In August 1606 King James, Anne of Denmark, her brother Christian IV of Denmark, and Prince Henry came to Upnor Castle by barge from Rochester. They had dinner aboard the Elizabeth Jonas. The ship was connected by a timber bridge to the Bear and a third boat or hulk served as a kitchen. The floating venue was devised by the naval engineer Phineas Pett. After dinner they took coaches from Upnor towards Gravesend, and stopped to watch cannon salutes from Windmill Hill. |
9535_13 | Upnor Castle fell into Parliamentary hands without a fight when the English Civil War broke out in 1642, and was subsequently used to intern Royalist officers. In May 1648, a Royalist uprising took place in Kent and Essex, with the royalists seizing a number of towns, including Gravesend, Rochester, Dover, and Maidstone. The Royalists were defeated in the Battle of Maidstone on 1 June, and the castle was restored to Parliamentary hands. Parliamentary commander-in-chief Sir Thomas Fairfax inspected the castle and ordered further repairs and strengthening of the gun platforms. It appears that the height of the gatehouse was also increased at this time, and the north and south towers were built up. They appear to have been left open at the back (on the landward side), but this was remedied in 1653 in the course of further repairs, making them suitable for use as troop accommodation.
Raid on the Medway |
9535_14 | The castle only saw action once in its history, during the Dutch Raid on the Medway in June 1667, part of the Second Anglo-Dutch War. The Dutch, under the nominal command of Lieutenant-Admiral Michiel de Ruyter, bombarded and captured the town of Sheerness, sailed up the Thames to Gravesend, then up the Medway to Chatham. They made their way past the chain that was supposed to block the river, sailed past the castle, and towed away HMS Royal Charles and Unity, as well as burning other ships at anchor. The Dutch anchored in the Medway overnight on 12 June, while the Duke of Albemarle took charge of the defences and ordered the hasty construction of an eight-gun battery next to Upnor Castle, using guns taken from Chatham. The castle's guns, the garrison's muskets, and the new battery were all used to bombard the Dutch ships when they attempted a second time to sail past Upnor to Chatham. The Dutch were able to burn some more ships in the anchorage, but they were unable to make further |
9535_15 | progress and had to withdraw. The outcome of the raid has been described as "the worst naval defeat England has ever sustained." |
9535_16 | The castle had acquitted itself well in the eyes of contemporary observers, despite its inability to prevent the raid, and the dedication of its garrison was praised. The pro-government London Gazette reported that "they were so warmly entertained by Major Scot, who commanded there [at Upnor], and on the other side by Sir Edward Spragg, from the Battery at the Shoare, that after very much Dammage received by them in the shattering of their ships, in sinking severall of their Long Boats manned out by them, in the great number of their Men kill'd, and some Prisoners taken, they were at the last forced to retire." Military historian Norman Longmate observes tartly, "in presenting damning facts in the most favourable light Charles [II's] ministers were unsurpassed." Samuel Pepys, secretary of the Navy Board, got closer to the truth when he noted in his diary that the castle's garrison were poorly provisioned: "I do not see that Upnor Castle hath received any hurt by them though they |
9535_17 | played long against it; and they themselves shot till they had hardly a gun left upon the carriages, so badly provided they were." |
9535_18 | Usage as a magazine and naval facility |
9535_19 | Upnor Castle had been neglected previously, but the Dutch attack prompted the government to order that it be maintained "as a fort and place of strength". In the end, the raid marked the end of the castle's career as a fortress. New and more powerful forts were built farther down the Medway and on the Isle of Grain with the aim of preventing enemies reaching Chatham, thus making the castle redundant. It was converted into "a Place of Stores and Magazines" in 1668 with a new purpose of supplying munitions to naval warships anchored in the Medway or the Swale. Guns, gun carriages, shot, and gunpowder were stored in great quantities within the main building of the castle, which had to be increased in height and its floors reinforced to accommodate the weight. By 1691, it was England's leading magazine, with 164 iron guns, 62 standing carriages, 100 ships' carriages, 7,125 pieces of iron shot, over 200 muskets of various types, 77 pikes, and 5,206 barrels of powder. This was considerably |
9535_20 | more than was held at the next largest magazine, the Tower of London. |
9535_21 | In 1811 a new magazine building was erected a little way downstream from the castle, relieving pressure on the castle. Upnor Castle ceased to be used as a storage magazine after 1827 and was converted into an Ordnance Laboratory (i.e. a workshop for filling explosive shells with gunpowder). Further storage space was required, and six hulks were moored alongside to serve as floating magazines; they remained even after a further magazine had been built ashore (1857). These storage problems were only alleviated when a further five large magazines, guarded by a barracks, were built inland at Chattenden (these were linked to Upnor via a 2 ft 6in (76 cm) narrow-gauge line built for steam locomotives). In 1891, the castle and its associated depot came under the full control of the Admiralty, ending an arrangement in which the War Office had managed the site with the Admiralty providing the funding. In 1899 it was noted that the castle was being used to store dry guncotton (a |
9535_22 | highly-flammable and dangerous explosive), while the less dangerous 'wet guncotton' form was kept on board the ever-present hulks moored nearby. This practice ceased soon afterwards, specialist storage magazines having been built alongside Chattenden at Lodge Hill. |
9535_23 | After the First World War, Upnor became a Royal Naval Armaments Depot (RNAD), one of a group of such facilities around the country. The castle and magazine were used for a time as a proofyard for testing firearms and explosives.
The castle remained in military ownership, but it became more of a museum from the 1920s onwards. During the Second World War, the castle was still in service as part of the Magazine Establishment and was damaged by two enemy bombs which fell in 1941. The bombing dislodged pieces of plaster in the castle's south tower and gatehouse, under which were discovered old graffiti, including a drawing of a ship dated to around 1700.
The castle today |
9535_24 | Following the end of the war in 1945, the Admiralty gave approval for Upnor Castle to be used as a Departmental Museum and to be opened to the public. It subsequently underwent a degree of restoration. The castle was scheduled as an Ancient Monument in January 1960 and is currently managed by English Heritage. It remains part of the Crown Estate.
Description |
9535_25 | Upnor Castle's buildings were constructed from a combination of Kentish ragstone and ashlar blocks, plus red bricks and timber. Its main building is a two-storeyed rectangular block that measures by , aligned in a north-east/south-west direction on the west bank of the Medway. Later known as the Magazine, it has been changed considerably since its original construction. It would have included limited barrack accommodation, possibly in a small second storey placed behind gun platforms on the roof. After the building was converted into a magazine in 1668 many changes were made which have obscured the earlier design. The second storey appears to have been extended across the full length of the building, covering over the earlier rooftop gun platforms. This gave more room for storage in the interior. The ground floor was divided into three compartments with a woodblock floor and copper-sheeted doors to reduce the risk of sparks. Further stores were housed on the first floor, with a |
9535_26 | windlass to raise stores from the waterside. |
9535_27 | A circular staircase within the building gives access to the castle's main gun platform or water bastion, a low triangular structure projecting into the river. The castle's main armament was mounted here in the open air; this is now represented by six mid-19th century guns that are still on their original carriages. There are nine embrasures in the bastion, six facing downstream and three upstream, with a rounded parapet designed to deflect shot. The water bastion was additionally protected by a wooden palisade that follows its triangular course a few metres further out in the river. The present palisade is a modern recreation of the original structure. |
9535_28 | A pair of towers stand on the river's edge a short distance on either side from the main building. They were originally two-storeyed open-backed structures with gun platforms situated on their first floors, providing flanking fire down the line of the ditch around the castle's perimeter. They were later adapted for use as accommodation, with their backs closed with bricks and the towers increased in height to provide a third storey. Traces of the gun embrasures can still be seen at the point where the original roofline was. The South Tower was said to have been for the use of the castle's governor, though their lack of comfort meant that successive governors declined to live there. The two towers are linked to the main building by a crenellated curtain wall where additional cannon were emplaced in two embrasures on the north parapet and one on the south. |
9535_29 | The castle's principal buildings are situated on the east side of a rectangular courtyard within which stand two large Turkey oaks, said to have been grown from acorns brought from Crimea after the Crimean War. A stone curtain wall topped with brick surrounds the courtyard, standing about thick and high. The courtyard is entered on the north-western side through a four-storeyed gatehouse with gun embrasures for additional defensive strength. It was substantially rebuilt in the 1650s after being badly damaged in a 1653 fire, traces of which can still be seen in the form of scorched stones on the first-floor walls. A central gateway with a round arch leads into a passage that gives access to the courtyard. Above the gateway is a late 18th-century clock that was inserted into the existing structure. A wooden bellcote was added in the early 19th century, and a modern flagpole surmounts the building. |
9535_30 | The curtain wall is surrounded by a dry ditch which was originally nearly wide by deep, though it has since been partially infilled. Visitors to the castle crossed a drawbridge, which is no longer extant, to reach the gatehouse. A secondary entrance to the castle is provided by a sally port in the north wall. On the inside of the curtain wall the brick foundations of buildings can still be seen. These were originally lean-to structures, constructed in the 17th century to provide storage facilities for the garrison.
Other associated buildings
Standing to the west of the castle, Upnor Castle House was built in the mid-17th century as accommodation for the Storekeeper, the officer in charge of the magazine. Expanded in the 18th century, it is now a private residence. |
9535_31 | A short distance to the south-west of the castle is a barracks block and associated storage buildings, constructed soon after 1718. Built to replace the original barrack accommodation within the castle when it was redeveloped to convert it into a magazine, it has changed little externally in the last 300 years. It is a rare surviving example of an 18th-century building of this type and was one of the first distinct barracks to be built in England. |
9535_32 | Depot buildings formerly associated with the castle still survive in the area immediately to the north-east. The earliest is a gunpowder magazine of 1857 (built to the same design as the 1810 magazine, which formerly stood alongside to the south but was demolished in the 1960s; these buildings had space for 33,000 barrels of powder between them). Between the magazines and the castle a Shifting House (for examining powder) had been built in 1811; both it and an adjacent shell store of 1857 were likewise demolished in 1964. They were constructed on top of earlier gun emplacements, of which earthwork traces can still be seen in the form of a broad bank running north-east from the castle towards the depot. A further four shell stores were built further to the north, together with other munitions stores, several of which remain. The Depot compound continued in Ministry of Defence hands until 2014, after which the area was due to be redeveloped as housing (with the surviving military |
9535_33 | buildings refurbished for light industrial use). |
9535_34 | References
External links
Upnor Castle – page at English Heritage
Information about the castle
History of Upnor Castle
Chatham's World Heritage Site application – including Upnor Castle
Castles in Kent
English Heritage sites in Kent
Forts in Medway
Grade I listed buildings in Kent
Military and war museums in England
Museums in Medway |
9536_0 | In a broad sense, a welder is anyone, amateur or professional, who uses welding equipment, perhaps especially one who uses such equipment fairly often. In a narrower sense, a welder is a tradesperson who specializes in fusing materials together. The term welder refers to the operator, the machine is referred to as the welding power supply. The materials to be joined can be metals (such as steel, aluminum, brass, stainless steel etc.) or varieties of plastic or polymer. Welders typically have to have good dexterity and attention to detail, as well as technical knowledge about the materials being joined and best practices in the field. |
9536_1 | Safety issues |
9536_2 | Welding, without the proper precautions appropriate for the process, can be a dangerous and unhealthy practice. However, with the use of new technology and proper protection, the risks of injury and death associated with welding can be greatly reduced. Because many common welding procedures involve an open electric arc or a flame, the risk of burns is significant. To prevent them, welders wear personal protective equipment in the form of heavy leather gloves and protective long sleeve jackets to avoid exposure to extreme heat and flames. Additionally, the brightness of the weld area leads to a condition called arc eye in which ultraviolet light causes the inflammation of the cornea and can burn the retinas of the eyes. Full face welding helmets with dark face plates are worn to prevent this exposure, and in recent years, new helmet models have been produced that feature a faceplate that self-darkens upon exposure to high amounts of UV light. To protect bystanders, opaque welding |
9536_3 | curtains often surround the welding area. These curtains, made of a polyvinyl chloride plastic film, shield nearby workers from exposure to the UV light from the electric arc, but should not be used to replace the filter glass used in helmets.<ref name="Cary">Cary, Howard B. and Scott C. Helzer (2005). Modern Welding Technology. Upper Saddle River, New Jersey: Pearson Education. .</ref> |
9536_4 | Welders are also often exposed to dangerous gases and particulate matter. Processes like flux-cored arc welding and shielded metal arc welding produce smoke containing particles of various types of oxides, which in some cases can lead to medical conditions like metal fume fever. The size of the particles in question tends to influence the toxicity of the fumes, with smaller particles presenting a greater danger. Additionally, many processes produce fumes and various gases, most commonly carbon dioxide and ozone, that can prove dangerous if ventilation is inadequate. Furthermore, because the use of compressed gases and flames in many welding processes pose an explosion and fire risk, some common precautions include limiting the amount of oxygen in the air and keeping combustible materials away from the workplace. Welders with expertise in welding pressurized vessels, including submarine hulls, industrial boilers, and power plant heat exchangers and boilers, are generally referred to |
9536_5 | as boilermakers. |
9536_6 | A lot of welders relate to getting small electrical shocks from their equipment. Occasionally, welders might work in damp crowded environments and they consider it to be a "part of the job." Welders can be shocked by faulty conditions in the welding circuit, or, from the work lead clamp, a grounded power tool that is on the bench (the workpiece or the electrode). All of these types of shocks come from the welding electrode terminal. Often these shocks are minor and are misdiagnosed as being an issue with a power tool or the power supply to the welder’s area. However, the more likely cause is from stray welding current which occurs when current from the welding cables leaks into the welder’s work area. Often this is not a serious problem, however, under the right circumstances, this can be fatal to the welder or anyone else inside the work area. When a welder feels a shock, they should take a minute to inspect the welding cables and ensure that they are clean and dry, and, that there |
9536_7 | are no cracks or gouges out of the rubber casing around the wire. These precautions may be life-saving to the welders. |
9536_8 | Notable welders |
9536_9 | Notable people who have worked as welders include:
İshak Alaton, Turkish businessman and investor
Steve Baer, passive-solar-energy designer/manufacturer, and author
Lucian Boz, Romanian literary critic, essayist, novelist, poet and translator
Bevan Braithwaite, chief executive of The Welding Institute
Hardcore Holly, American semi-retired professional wrestler
Mark Honadel, American businessman, former professional metal fabricator, welding instructor, industrial manager and politician
William A. Schmidt, American welder, shop foreman and politician
Stefan Löfven, Prime Minister of Sweden
Werner Herzog, German film director
Honoré Sharrer, American painter
Mohammad Abbas (cricketer), Pakistani cricketer
Jesse James (entrepreneur) West Coast Choppers custom vehicle maker and American television personality
Jessi Combs Host of Overhaulin', American professional racer, television personality, and metal fabricator. |
9536_10 | Paul Teutul Sr. Founder of Orange County Choppers, Custom Motorcycle Manufacturing
Paul Teutul Jr. Co-Owner of Orange County Choppers, Custom Motorcycle Manufacturing
Billy Connolly Scottish Stand-up Comedian, Actor, Welded at a Shipyard in his youth.
Nyu Kok Meng, a Malaysian who formerly worked as a welder in Singapore prior to becoming an armed robber in the high-profile 1983 Andrew Road triple murders. He was currently released since 2005 after serving a life sentence and receiving 6 strokes of the cane for armed robbery. |
9536_11 | See also
References
Further reading
ASM International (2003). Trends in Welding Research. Materials Park, Ohio: ASM International.
Hicks, John (1999). Welded Joint Design. New York: Industrial Press. .
Kalpakjian, Serope and Steven R. Schmid (2001). Manufacturing Engineering and Technology''. Prentice Hall. .
Construction trades workers
Metalworking occupations
Production occupations |
9537_0 | An avalanche (also called a snow slide) is a rapid flow of snow down a slope, such as a hill or mountain.
Avalanches can be set off spontaneously, by such factors as increased precipitation or snow pack weakening, or by external means such as humans, animals, and earthquakes. Primarily composed of flowing snow and air, large avalanches have the capability to capture and move ice, rocks, and trees.
Avalanches occur in two general forms, or combinations thereof: slab avalanches made of tightly packed snow, triggered by a collapse of an underlying weak snow layer, and loose snow avalanches made of looser snow. After being set off, avalanches usually accelerate rapidly and grow in mass and volume as they capture more snow. If an avalanche moves fast enough, some of the snow may mix with the air, forming a powder snow avalanche. |
9537_1 | Though they appear to share similarities, avalanches are distinct from slush flows, mudslides, rock slides, and serac collapses. They are also different from large scale movements of ice.
Avalanches can happen in any mountain range that has an enduring snowpack. They are most frequent in winter or spring, but may occur at any time of year. In mountainous areas, avalanches are among the most serious natural hazards to life and property, so great efforts are made in avalanche control.
There are many classification systems for the different forms of avalanches, which vary according to their users' needs. Avalanches can be described by their size, destructive potential, initiation mechanism, composition, and dynamics.
Formation |
9537_2 | Most avalanches occur spontaneously during storms under increased load due to snowfall and/or erosion. The second largest cause of natural avalanches is metamorphic changes in the snowpack such as melting due to solar radiation. Other natural causes include rain, earthquakes, rockfall and icefall. Artificial triggers of avalanches include skiers, snowmobiles, and controlled explosive work. Contrary to popular belief, avalanches are not triggered by loud sound; the pressure from sound is orders of magnitude too small to trigger an avalanche.
Avalanche initiation can start at a point with only a small amount of snow moving initially; this is typical of wet snow avalanches or avalanches in dry unconsolidated snow. However, if the snow has sintered into a stiff slab overlying a weak layer then fractures can propagate very rapidly, so that a large volume of snow, that may be thousands of cubic meters, can start moving almost simultaneously. |
9537_3 | A snowpack will fail when the load exceeds the strength. The load is straightforward; it is the weight of the snow. However, the strength of the snowpack is much more difficult to determine and is extremely heterogeneous. It varies in detail with properties of the snow grains, size, density, morphology, temperature, water content; and the properties of the bonds between the grains. These properties may all metamorphose in time according to the local humidity, water vapour flux, temperature and heat flux. The top of the snowpack is also extensively influenced by incoming radiation and the local air flow. One of the aims of avalanche research is to develop and validate computer models that can describe the evolution of the seasonal snowpack over time. A complicating factor is the complex interaction of terrain and weather, which causes significant spatial and temporal variability of the depths, crystal forms, and layering of the seasonal snowpack. |
9537_4 | Slab avalanches
Slab avalanches form frequently in snow that has been deposited, or redeposited by wind. They have the characteristic appearance of a block (slab) of snow cut out from its surroundings by fractures. Elements of slab avalanches include the following: a crown fracture at the top of the start zone, flank fractures on the sides of the start zones, and a fracture at the bottom called the stauchwall. The crown and flank fractures are vertical walls in the snow delineating the snow that was entrained in the avalanche from the snow that remained on the slope. Slabs can vary in thickness from a few centimetres to three metres. Slab avalanches account for around 90% of avalanche-related fatalities in backcountry users.
Powder snow avalanches |
9537_5 | The largest avalanches form turbulent suspension currents known as powder snow avalanches or mixed avalanches, a kind of gravity current. These consist of a powder cloud, which overlies a dense avalanche. They can form from any type of snow or initiation mechanism, but usually occur with fresh dry powder. They can exceed speeds of , and masses of 10,000,000 tonnes; their flows can travel long distances along flat valley bottoms and even uphill for short distances.
Wet snow avalanches |
9537_6 | In contrast to powder snow avalanches, wet snow avalanches are a low velocity suspension of snow and water, with the flow confined to the track surface (McClung, first edition 1999, page 108). The low speed of travel is due to the friction between the sliding surface of the track and the water saturated flow. Despite the low speed of travel (~10–40 km/h), wet snow avalanches are capable of generating powerful destructive forces, due to the large mass and density. The body of the flow of a wet snow avalanche can plough through soft snow, and can scour boulders, earth, trees, and other vegetation; leaving exposed and often scored ground in the avalanche track. Wet snow avalanches can be initiated from either loose snow releases, or slab releases, and only occur in snow packs that are water saturated and isothermally equilibrated to the melting point of water. The isothermal characteristic of wet snow avalanches has led to the secondary term of isothermal slides found in the literature |
9537_7 | (for example in Daffern, 1999, page 93). At temperate latitudes wet snow avalanches are frequently associated with climatic avalanche cycles at the end of the winter season, when there is significant daytime warming. |
9537_8 | Ice avalanche
An ice avalanche occurs when a large piece of ice, such as from a serac or calving glacier, falls onto ice (such as the Khumbu Icefall), triggering a movement of broken ice chunks. The resulting movement is more analogous to a rockfall or a landslide than a snow avalanche. They are typically very difficult to predict and almost impossible to mitigate. |
9537_9 | Avalanche pathway
As an avalanche moves down a slope it follows a certain pathway that is dependent on the slope's degree of steepness and the volume of snow/ice involved in the mass movement. The origin of an avalanche is called the Starting Point and typically occurs on a 30–45 degree slope. The body of the pathway is called the Track of the avalanche and usually occurs on a 20–30 degree slope. When the avalanche loses its momentum and eventually stops it reaches the Runout Zone. This usually occurs when the slope has reached a steepness that is less than 20 degrees. These degrees are not consistently true due to the fact that each avalanche is unique depending on the stability of the snowpack that it was derived from as well as the environmental or human influences that triggered the mass movement. |
9537_10 | Death caused by avalanche
People caught in avalanches can die from suffocation, trauma, or hypothermia. On average, 28 people die in avalanches every winter in the United States. Globally, an average of over 150 people die each year from avalanches. Three of the deadliest recorded avalanches have killed over a thousand people each.
Terrain, snowpack, weather
Doug Fesler and Jill Fredston developed a conceptual model of the three primary elements of avalanches: terrain, weather, and snowpack. Terrain describes the places where avalanches occur, weather describes the meteorological conditions that create the snowpack, and snowpack describes the structural characteristics of snow that make avalanche formation possible. |
9537_11 | Terrain
Avalanche formation requires a slope shallow enough for snow to accumulate but steep enough for the snow to accelerate once set in motion by the combination of mechanical failure (of the snowpack) and gravity. The angle of the slope that can hold snow, called the angle of repose, depends on a variety of factors such as crystal form and moisture content. Some forms of drier and colder snow will only stick to shallower slopes, while wet and warm snow can bond to very steep surfaces. In particular, in coastal mountains, such as the Cordillera del Paine region of Patagonia, deep snow packs collect on vertical and even overhanging rock faces. The slope angle that can allow moving snow to accelerate depends on a variety of factors such as the snow's shear strength (which is itself dependent upon crystal form) and the configuration of layers and inter-layer interfaces. |
9537_12 | The snowpack on slopes with sunny exposures is strongly influenced by sunshine. Diurnal cycles of thawing and refreezing can stabilize the snowpack by promoting settlement. Strong freeze-thaw cycles result in the formation of surface crusts during the night and of unstable surface snow during the day. Slopes in the lee of a ridge or of another wind obstacle accumulate more snow and are more likely to include pockets of deep snow, wind slabs, and cornices, all of which, when disturbed, may result in avalanche formation. Conversely, the snowpack on a windward slope is often much shallower than on a lee slope. |
9537_13 | Avalanches and avalanche paths share common elements: a start zone where the avalanche originates, a track along which the avalanche flows, and a runout zone where the avalanche comes to rest. The debris deposit is the accumulated mass of the avalanched snow once it has come to rest in the run-out zone. For the image at left, many small avalanches form in this avalanche path every year, but most of these avalanches do not run the full vertical or horizontal length of the path. The frequency with which avalanches form in a given area is known as the return period. |
9537_14 | The start zone of an avalanche must be steep enough to allow snow to accelerate once set in motion, additionally convex slopes are less stable than concave slopes, because of the disparity between the tensile strength of snow layers and their compressive strength. The composition and structure of the ground surface beneath the snowpack influences the stability of the snowpack, either being a source of strength or weakness. Avalanches are unlikely to form in very thick forests, but boulders and sparsely distributed vegetation can create weak areas deep within the snowpack through the formation of strong temperature gradients. Full-depth avalanches (avalanches that sweep a slope virtually clean of snow cover) are more common on slopes with smooth ground, such as grass or rock slabs. |
9537_15 | Generally speaking, avalanches follow drainages down-slope, frequently sharing drainage features with summertime watersheds. At and below tree line, avalanche paths through drainages are well defined by vegetation boundaries called trim lines, which occur where avalanches have removed trees and prevented regrowth of large vegetation. Engineered drainages, such as the avalanche dam on Mount Stephen in Kicking Horse Pass, have been constructed to protect people and property by redirecting the flow of avalanches. Deep debris deposits from avalanches will collect in catchments at the terminus of a run out, such as gullies and river beds. |
9537_16 | Slopes flatter than 25 degrees or steeper than 60 degrees typically have a lower incidence of avalanches. Human-triggered avalanches have the greatest incidence when the snow's angle of repose is between 35 and 45 degrees; the critical angle, the angle at which human-triggered avalanches are most frequent, is 38 degrees. When the incidence of human triggered avalanches is normalized by the rates of recreational use, however, hazard increases uniformly with slope angle, and no significant difference in hazard for a given exposure direction can be found. The rule of thumb is: A slope that is flat enough to hold snow but steep enough to ski has the potential to generate an avalanche, regardless of the angle.
Snowpack structure and characteristics |
9537_17 | The snowpack is composed of ground-parallel layers that accumulate over the winter. Each layer contains ice grains that are representative of the distinct meteorological conditions during which the snow formed and was deposited. Once deposited, a snow layer continues to evolve under the influence of the meteorological conditions that prevail after deposition. |
9537_18 | For an avalanche to occur, it is necessary that a snowpack have a weak layer (or instability) below a slab of cohesive snow. In practice the formal mechanical and structural factors related to snowpack instability are not directly observable outside of laboratories, thus the more easily observed properties of the snow layers (e.g. penetration resistance, grain size, grain type, temperature) are used as index measurements of the mechanical properties of the snow (e.g. tensile strength, friction coefficients, shear strength, and ductile strength). This results in two principal sources of uncertainty in determining snowpack stability based on snow structure: First, both the factors influencing snow stability and the specific characteristics of the snowpack vary widely within small areas and time scales, resulting in significant difficulty extrapolating point observations of snow layers across different scales of space and time. Second, the relationship between readily observable snowpack |
9537_19 | characteristics and the snowpack's critical mechanical properties has not been completely developed. |
9537_20 | While the deterministic relationship between snowpack characteristics and snowpack stability is still a matter of ongoing scientific study, there is a growing empirical understanding of the snow composition and deposition characteristics that influence the likelihood of an avalanche. Observation and experience has shown that newly fallen snow requires time to bond with the snow layers beneath it, especially if the new snow falls during very cold and dry conditions. If ambient air temperatures are cold enough, shallow snow above or around boulders, plants, and other discontinuities in the slope, weakens from rapid crystal growth that occurs in the presence of a critical temperature gradient. Large, angular snow crystals are indicators of weak snow, because such crystals have fewer bonds per unit volume than small, rounded crystals that pack tightly together. Consolidated snow is less likely to slough than loose powdery layers or wet isothermal snow; however, consolidated snow is a |
9537_21 | necessary condition for the occurrence of slab avalanches, and persistent instabilities within the snowpack can hide below well-consolidated surface layers. Uncertainty associated with the empirical understanding of the factors influencing snow stability leads most professional avalanche workers to recommend conservative use of avalanche terrain relative to current snowpack instability. |
9537_22 | Weather |
9537_23 | Avalanches only occur in a standing snowpack. Typically winter seasons at high latitudes, high altitudes, or both have weather that is sufficiently unsettled and cold enough for precipitated snow to accumulate into a seasonal snowpack. Continentality, through its potentiating influence on the meteorological extremes experienced by snow packs, is an important factor in the evolution of instabilities, and consequential occurrence of avalanches faster stabilization of the snowpack after storm cycles. The evolution of the snowpack is critically sensitive to small variations within the narrow range of meteorological conditions that allow for the accumulation of snow into a snowpack. Among the critical factors controlling snowpack evolution are: heating by the sun, radiational cooling, vertical temperature gradients in standing snow, snowfall amounts, and snow types. Generally, mild winter weather will promote the settlement and stabilization of the snowpack; conversely, very cold, windy, |
9537_24 | or hot weather will weaken the snowpack. |
9537_25 | At temperatures close to the freezing point of water, or during times of moderate solar radiation, a gentle freeze-thaw cycle will take place. The melting and refreezing of water in the snow strengthens the snowpack during the freezing phase and weakens it during the thawing phase. A rapid rise in temperature, to a point significantly above the freezing point of water, may cause avalanche formation at any time of year. |
9537_26 | Persistent cold temperatures can either prevent new snow from stabilizing or destabilize the existing snowpack. Cold air temperatures on the snow surface produce a temperature gradient in the snow, because the ground temperature at the base of the snowpack is usually around 0 °C, and the ambient air temperature can be much colder. When a temperature gradient greater than 10 °C change per vertical meter of snow is sustained for more than a day, angular crystals called depth hoar or facets begin forming in the snowpack because of rapid moisture transport along the temperature gradient. These angular crystals, which bond poorly to one another and the surrounding snow, often become a persistent weakness in the snowpack. When a slab lying on top of a persistent weakness is loaded by a force greater than the strength of the slab and persistent weak layer, the persistent weak layer can fail and generate an avalanche. |
9537_27 | Any wind stronger than a light breeze can contribute to a rapid accumulation of snow on sheltered slopes downwind. Wind slabs form quickly and, if present, weaker snow below the slab may not have time to adjust to the new load. Even on a clear day, wind can quickly load a slope with snow by blowing snow from one place to another. Top-loading occurs when wind deposits snow from the top of a slope; cross-loading occurs when wind deposits snow parallel to the slope. When a wind blows over the top of a mountain, the leeward, or downwind, side of the mountain experiences top-loading, from the top to the bottom of that lee slope. When the wind blows across a ridge that leads up the mountain, the leeward side of the ridge is subject to cross-loading. Cross-loaded wind-slabs are usually difficult to identify visually. |
9537_28 | Snowstorms and rainstorms are important contributors to avalanche danger. Heavy snowfall will cause instability in the existing snowpack, both because of the additional weight and because the new snow has insufficient time to bond to underlying snow layers. Rain has a similar effect. In the short-term, rain causes instability because, like a heavy snowfall, it imposes an additional load on the snowpack; and, once rainwater seeps down through the snow, it acts as a lubricant, reducing the natural friction between snow layers that holds the snowpack together. Most avalanches happen during or soon after a storm. |
9537_29 | Daytime exposure to sunlight will rapidly destabilize the upper layers of the snowpack if the sunlight is strong enough to melt the snow, thereby reducing its hardness. During clear nights, the snowpack can re-freeze when ambient air temperatures fall below freezing, through the process of long-wave radiative cooling, or both. Radiative heat loss occurs when the night air is significantly cooler than the snowpack, and the heat stored in the snow is re-radiated into the atmosphere. |
9537_30 | Dynamics
When a slab avalanche forms, the slab disintegrates into increasingly smaller fragments as the snow travels downhill. If the fragments become small enough the outer layer of the avalanche, called a saltation layer, takes on the characteristics of a fluid. When sufficiently fine particles are present they can become airborne and, given a sufficient quantity of airborne snow, this portion of the avalanche can become separated from the bulk of the avalanche and travel a greater distance as a powder snow avalanche. Scientific studies using radar, following the 1999 Galtür avalanche disaster, confirmed the hypothesis that a saltation layer forms between the surface and the airborne components of an avalanche, which can also separate from the bulk of the avalanche.<ref>Horizon: Anatomy of an Avalanche, BBC', 1999-11-25</ref> |
9537_31 | Driving an avalanche is the component of the avalanche's weight parallel to the slope; as the avalanche progresses any unstable snow in its path will tend to become incorporated, so increasing the overall weight. This force will increase as the steepness of the slope increases, and diminish as the slope flattens. Resisting this are a number of components that are thought to interact with each other: the friction between the avalanche and the surface beneath; friction between the air and snow within the fluid; fluid-dynamic drag at the leading edge of the avalanche; shear resistance between the avalanche and the air through which it is passing, and shear resistance between the fragments within the avalanche itself. An avalanche will continue to accelerate until the resistance exceeds the forward force. |
9537_32 | Modelling
Attempts to model avalanche behaviour date from the early 20th century, notably the work of Professor Lagotala in preparation for the 1924 Winter Olympics in Chamonix. His method was developed by A. Voellmy and popularised following the publication in 1955 of his Ueber die Zerstoerungskraft von Lawinen (On the Destructive Force of Avalanches).
Voellmy used a simple empirical formula, treating an avalanche as a sliding block of snow moving with a drag force that was proportional to the square of the speed of its flow:
He and others subsequently derived other formulae that take other factors into account, with the Voellmy-Salm-Gubler and the Perla-Cheng-McClung models becoming most widely used as simple tools to model flowing (as opposed to powder snow) avalanches. |
9537_33 | Since the 1990s many more sophisticated models have been developed. In Europe much of the recent work was carried out as part of the SATSIE (Avalanche Studies and Model Validation in Europe) research project supported by the European Commission which produced the leading-edge MN2L model, now in use with the Service Restauration des Terrains en Montagne (Mountain Rescue Service) in France, and D2FRAM (Dynamical Two-Flow-Regime Avalanche Model), which was still undergoing validation as of 2007. Other known models are the SAMOS-AT avalanche simulation software and the RAMMS software.
Human involvement
Prevention |
9537_34 | Preventative measures are employed in areas where avalanches pose a significant threat to people, such as ski resorts, mountain towns, roads, and railways. There are several ways to prevent avalanches and lessen their power and develop preventative measures to reduce the likelihood and size of avalanches by disrupting the structure of the snowpack, while passive measures reinforce and stabilize the snowpack in situ. The simplest active measure is repeatedly traveling on a snowpack as snow accumulates; this can be by means of boot-packing, ski-cutting, or machine grooming. Explosives are used extensively to prevent avalanches, by triggering smaller avalanches that break down instabilities in the snowpack, and removing overburden that can result in larger avalanches. Explosive charges are delivered by a number of methods including hand-tossed charges, helicopter-dropped bombs, Gazex concussion lines, and ballistic projectiles launched by air cannons and artillery. Passive preventive |
9537_35 | systems such as snow fences and light walls can be used to direct the placement of snow. Snow builds up around the fence, especially the side that faces the prevailing winds. Downwind of the fence, snow build-up is lessened. This is caused by the loss of snow at the fence that would have been deposited and the pickup of the snow that is already there by the wind, which was depleted of snow at the fence. When there is a sufficient density of trees, they can greatly reduce the strength of avalanches. They hold snow in place and when there is an avalanche, the impact of the snow against the trees slows it down. Trees can either be planted or they can be conserved, such as in the building of a ski resort, to reduce the strength of avalanches. |
9537_36 | In turn, socio-environmental changes can influence the occurrence of damaging avalanches: some studies linking changes in land-use/land-cover patterns and the evolution of snow avalanche damage in mid latitude mountains show the importance of the role played by vegetation cover, that is at the root of the increase of damage when the protective forest is deforested (because of demographic growth, intensive grazing and industrial or legal causes), and at the root of the decrease of damage because of the transformation of a traditional land-management system based on overexploitation into a system based on land marginalization and reforestation, something that has happened mainly since the mid-20th century in mountain environments of developed countries
Mitigation |
9537_37 | In many areas, regular avalanche tracks can be identified and precautions can be taken to minimize damage, such as the prevention of development in these areas. To mitigate the effect of avalanches the construction of artificial barriers can be very effective in reducing avalanche damage. There are several types: One kind of barrier (snow net) uses a net strung between poles that are anchored by guy wires in addition to their foundations. These barriers are similar to those used for rockslides. Another type of barrier is a rigid fence-like structure (snow fence) and may be constructed of steel, wood or pre-stressed concrete. They usually have gaps between the beams and are built perpendicular to the slope, with reinforcing beams on the downhill side. Rigid barriers are often considered unsightly, especially when many rows must be built. They are also expensive and vulnerable to damage from falling rocks in the warmer months. In addition to industrially manufactured barriers, |
9537_38 | landscaped barriers, called avalanche dams stop or deflect avalanches with their weight and strength. These barriers are made out of concrete, rocks, or earth. They are usually placed right above the structure, road, or railway that they are trying to protect, although they can also be used to channel avalanches into other barriers. Occasionally, earth mounds are placed in the avalanche's path to slow it down. Finally, along transportation corridors, large shelters, called snow sheds, can be built directly in the slide path of an avalanche to protect traffic from avalanches. |
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