1.
Mount Lafayette
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Mount Lafayette is a 5, 249-foot mountain at the northern end of the Franconia Range in the White Mountains of New Hampshire, United States. It lies in the town of Franconia in Grafton County, the mountains upper reaches are located in the alpine zone, an area where only dwarf vegetation exists due to the harsh climate. Mount Lafayette is the highest point in the Franconia Range, a line of peaks along the east side of Franconia Notch and it is the sixth highest peak in New Hampshire and the highest outside of the Presidential Range. It is the second most prominent peak in the state, on the western side, its lower slopes lie inside Franconia Notch State Park. The remainder of the lies within the White Mountain National Forest. The summit marks the border of the Pemigewasset Wilderness Area within the WMNF. A variety of lead up over 3,000 vertical feet to its exposed summit. The Greenleaf Trail begins at the lot for the Cannon Mountain tramway and ascends to the Appalachian Mountain Clubs Greenleaf Hut. The peak is at the junction of the Garfield Ridge Trail, which follows the ridge northeast to Mount Garfield, and the Franconia Ridge Trail, which leads south to Mounts Lincoln, Liberty, and Flume. Both the Garfield Ridge Trail and the Franconia Ridge Trail form part of the Appalachian Trail, a very popular hike is to make a loop combining the three most notable summits of the Franconia Range. The loop starts with the Old Bridle Path to the AMC Greenleaf Hut, from there, one takes the Greenleaf Trail to the summit of Mt. Lafayette. This loop is 8.9 miles long, with an elevation gain of about 3,900 feet. The mountain is named to honor General Lafayette, a French military hero who fought with and significantly aided the Continental Army during the American Revolutionary War
2.
Mountain hut
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A mountain hut is a building located high in the mountains, generally accessible only by foot, intended to provide food and shelter to mountaineers, climbers and hikers. Mountain huts are usually operated by an Alpine Club or some organisation dedicated to hiking or mountain recreation, Mountain huts can provide a range of services, starting with shelter and simple sleeping berths. Mountain huts usually allow anybody to access their facilities, although some require reservations, the Swiss Alpine Club has built huts since 1863. In the United States, the Appalachian Mountain Club built its first hut at Madison Spring in New Hampshire in 1888-89, the construction of refuges and shelters in the Alps date back to ancient times, when Roman roads led across the mountain passes. In the High Middle Ages, hospitales were erected along the routes, cottages. The long history of mountaineering from the 19th century onwards has led to a number of Alpine club huts as well as private huts along the mountaineering paths. These huts are categorised according to their location and facilities and they may have beds or a mattress room for overnight stays. Many climbing clubs in the UK have such huts in Snowdonia or in the Lake District, a well-known example is the Charles Inglis Clark Memorial Hut under the northern crags of Ben Nevis in Scotland - this is a purpose-built hut, high up the mountain. In the Slovakia there is a network of mountain huts in most mountain and forest regions. In the past they were managed by the official tourist union, official mountain huts are similar to guest houses and are run by full-time managers. The Norwegian Trekking Association operates about 460 cabins mostly in the mountains and in forested areas, many cabins are unstaffed and open all year, while the staffed cabins often are just open during summer. In Poland most of mountains shelters and huts are run by PTTK - Polish Tourist Society, only few of shelters belong to private investors. Most of mountains shelters offer only common sleeping rooms and refreshments, Polish mountain huts are obliged by their own regulations to overnight each person who is not able to find any other place before sunset, though the conditions may be tough. The hut shall provide each tourist or hiker with free boiling water for hot drinks, there are many huts in the United States, in the Rocky Mountains, the Appalachian Mountains and other ranges. There are also many mountain huts throughout Maine, the Alpine Club of Canada operates what it calls the largest network of backcountry huts in North America. The New Zealand Department of Conservation manages a network of over 950 huts of all shapes and sizes, the mountains of Asia do not have a well-developed system of public mountain huts, although hiking, trekking and mountain climbing are common. In 2015, a competition was launched to design huts that could be located along trekking trails of Nepal
3.
White Mountains (New Hampshire)
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The White Mountains are a mountain range covering about a quarter of the state of New Hampshire and a small portion of western Maine in the United States. They are part of the northern Appalachian Mountains and the most rugged mountains in New England, the range is heavily visited due to its proximity to Boston and, to a lesser extent, New York City and Montreal. Most of the area is land, including the White Mountain National Forest. Its most famous mountain is 6, 288-foot Mount Washington, which is the highest peak in the Northeastern U. S. Mount Washington is part of a line of summits, the Presidential Range, that are named after U. S. presidents and other prominent Americans. The White Mountains also include the Franconia Range, Sandwich Range, Carter-Moriah Range and Kinsman Range in New Hampshire, in all, there are 48 peaks within New Hampshire as well as one in Maine over 4,000 feet, known as the Four-thousand footers. The Whites are known for a system of alpine huts for hikers operated by the Appalachian Mountain Club, the Appalachian Trail crosses the area from southwest to northeast. It is not clear where the name White Mountains came from, there is no record of what Native Americans called the range, although pre-Colonial names for many individual peaks are known. The name and similar such as White Hills or Wine Hills are found in literature from Colonial times. According to tradition, the mountains were first sighted from shipboard off the coast near the Piscataqua estuary, the highest peaks would often be snow-capped, appearing white. An alternate theory is that the granite of the summits looked white to observers. The White Mountains are a section of the larger New England province. The magma intrusions forming the White Mountains today were created 124 to 100 million years ago as the North American Plate moved westward over the New England hotspot, widespread evidence of glaciation may be seen in the U-shaped form of various notches, or mountain passes. Glacial cirques form the heads of Tuckerman Ravine on Mt. Washington, glacial striations are visible at numerous locations, including on the exposed rocks at the summit of Pine Mountain in Gorham. The Mount Washington Auto Road and the historic Mount Washington Cog Railway ascend the ranges highest peak, heavily visited Arethusa Falls, the second tallest waterfall in New Hampshire, lies on a southwest flank of Crawford Notch. The Old Man of the Mountain, a formation on Cannon Mountain that resembled the craggy profile of a mans face, was a White Mountain landmark until it fell in May 2003. It remains the symbol of New Hampshire. The range also includes a feature dubbed The Basin, consisting of a granite bowl,20 feet in diameter, fed by a waterfall. The areas around The Basin are popular spots for swimming in the ice-cold mountain-fed water, some of the earliest maps of the White Mountains were produced as tourist maps and not topographical maps
4.
New Hampshire
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New Hampshire is a state in the New England region of the northeastern United States. It is bordered by Massachusetts to the south, Vermont to the west, Maine and the Atlantic Ocean to the east, New Hampshire is the 5th smallest by land area and the 9th least populous of the 50 United States. Concord is the capital, while Manchester is the largest city in the state and in northern New England, including Vermont. It has no sales tax, nor is personal income taxed at either the state or local level. The New Hampshire primary is the first primary in the U. S. presidential election cycle and its license plates carry the state motto, Live Free or Die. The states nickname, The Granite State, refers to its extensive granite formations, the state was named after the southern English county of Hampshire by Captain John Mason. New Hampshire is part of the New England region and it is bounded by Quebec, Canada, to the north and northwest, Maine and the Atlantic Ocean to the east, Massachusetts to the south, and Vermont to the west. New Hampshires major regions are the Great North Woods, the White Mountains, the Lakes Region, the Seacoast, the Merrimack Valley, the Monadnock Region, and the Dartmouth-Lake Sunapee area. New Hampshire has the shortest ocean coastline of any U. S. coastal state, New Hampshire was home to the rock formation called the Old Man of the Mountain, a face-like profile in Franconia Notch, until the formation disintegrated in May 2003. Major rivers include the 110-mile Merrimack River, which bisects the lower half of the state north–south and ends up in Newburyport and its tributaries include the Contoocook River, Pemigewasset River, and Winnipesaukee River. The 410-mile Connecticut River, which starts at New Hampshires Connecticut Lakes and flows south to Connecticut, only one town – Pittsburg – shares a land border with the state of Vermont. The northwesternmost headwaters of the Connecticut also define the Canada–U. S, the Piscataqua River and its several tributaries form the states only significant ocean port where they flow into the Atlantic at Portsmouth. The Salmon Falls River and the Piscataqua define the southern portion of the border with Maine, the U. S. Supreme Court dismissed the case in 2002, leaving ownership of the island with Maine. New Hampshire still claims sovereignty of the base, however, the largest of New Hampshires lakes is Lake Winnipesaukee, which covers 71 square miles in the east-central part of New Hampshire. Umbagog Lake along the Maine border, approximately 12.3 square miles, is a distant second, Squam Lake is the second largest lake entirely in New Hampshire. New Hampshire has the shortest ocean coastline of any state in the United States, Hampton Beach is a popular local summer destination. It is the state with the highest percentage of area in the country. New Hampshire is in the temperate broadleaf and mixed forests biome, much of the state, in particular the White Mountains, is covered by the conifers and northern hardwoods of the New England-Acadian forests
5.
Alps
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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, Mont Blanc spans the French–Italian border, and at 4,810 m is the highest mountain in the Alps. The Alpine region area contains about a hundred peaks higher than 4000 metres, the altitude and size of the range affects the climate in Europe, in the mountains precipitation levels vary greatly and climatic conditions consist of distinct zones. Wildlife such as live in the higher peaks to elevations of 3,400 m. 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, and the Romans had settlements in the region. In 1800 Napoleon crossed one of the passes with an army of 40,000. The 18th and 19th centuries saw an influx of naturalists, writers, in World War II, Adolf Hitler kept a base of operation in the Bavarian Alps throughout the war. The Alpine region has a cultural identity. The Winter Olympic Games have been hosted in the Swiss, French, at present, the region is home to 14 million people and 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 and this may be consistent with the theory that in Greek Alpes is a name of non-Indo-European origin. According to the Old English Dictionary, the Latin Alpes might possibly 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, in modern languages the term alp, alm, albe or alpe refers to a grazing pastures in the alpine regions below the glaciers, not the peaks. An alp refers to a mountain pasture where cows are taken to be grazed during the summer months and where hay barns can be found. 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, the range continues onward toward Vienna, Austria, and east to the Adriatic Sea and Slovenia. To the south it dips into northern Italy and to the north extends to the border of Bavaria in Germany
6.
Appalachian Trail
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The trail is about 2,200 miles long, though the exact length changes over time as parts are modified or rerouted. More than 2 million people are said to do at least one day-hike on the each year. The idea of the Appalachian Trail came about in 1921, the trail itself was completed in 1937 after more than a decade of work, although improvements and changes continue. It is maintained by 31 trail clubs and multiple partnerships, and managed by the National Park Service, United States Forest Service, the majority of the trail is in forest or wild lands, although some portions traverse towns, roads and farms. The trail conservancy claims that the Appalachian Trail is the longest hiking-only trail in the world. It passes through 14 states, Georgia, North Carolina, Tennessee, Virginia, West Virginia, Maryland, Pennsylvania, New Jersey, New York, Connecticut, Massachusetts, Vermont, New Hampshire, and Maine. Many books, memoirs, websites, and fan organizations are dedicated to these pursuits, other separate extensions continue the southern end of the Appalachian range in Alabama and continue south into Florida, creating what is known as the Eastern Continental Trail. The Appalachian Trail, the Continental Divide Trail, and the Pacific Crest Trail form what is known as the Triple Crown of Hiking in the United States. The trail was conceived by Benton MacKaye, a forester who wrote his original plan—called An Appalachian Trail, macKayes idea detailed a grand trail that would connect a series of farms and wilderness work/study camps for city-dwellers. The idea was adopted by the new Palisades Interstate Park Trail Conference as their main project. On October 7,1923, the first section of the trail, from Bear Mountain west through Harriman State Park to Arden, MacKaye then called for a two-day Appalachian Trail conference to be held in March 1925 in Washington, D. C. This meeting inspired the formation of the Appalachian Trail Conference, a retired judge named Arthur Perkins and his younger associate Myron Avery took up the cause. Andersons efforts helped spark renewed interest in the trail, and Avery was able to bring other states on board, upon taking over the ATC, Avery adopted the more practical goal of building a simple hiking trail. He and MacKaye clashed over the ATCs response to a commercial development along the trails path, MacKaye left the organization. Avery reigned as Chairman of the ATC from 1932 to 1952, Avery became the first to walk the trail end-to-end, though not as a thru-hike, in 1936. In August 1937, the trail was completed to Sugarloaf Mountain in Maine, the ATCs trail crews and volunteer trail-maintaining clubs have relocated or rehabilitated miles of trail since that time. The completed thru-hike was much later recorded and accepted by the Appalachian Long Distance Hikers Association, in 1948, Earl Shaffer of York, Pennsylvania, brought a great deal of attention to the project by publicizing the first claimed thru-hike. The claim was criticized for the hikes omission of significant portions due to short-cuts
7.
Tree line
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The tree line is the edge of the habitat at which trees are capable of growing. It is found at high elevations and in frigid environments, beyond the tree line, trees cannot tolerate the environmental conditions. The tree line should not be confused with a lower timberline or forest line, at the tree line, tree growth is often sparse and stunted, with the last trees forming densely matted bushes, known as krummholz. The tree line, like other natural lines, appears well-defined from a distance. Trees grow shorter towards the inhospitable climate until they stop growing. The climate above the line of mountains is called an alpine climate. In the northern hemisphere treelines on north-facing slopes are lower than on south-facing slopes because the increased shade on north-facing slopes means the snowpack takes longer to melt and this shortens the growing season for trees. In the southern hemisphere, the slopes have the shorter growing season. The alpine tree line boundary is seldom abrupt, it forms a transition zone between closed forest below and treeless alpine tundra above. Environmentally dwarfed shrubs commonly forms the upper limit, the decrease in air temperature due to increasing elevation causes the alpine climate. Skin effects and topography can create microclimates that alter the general cooling trend, however, the number of degree days calculated from leaf temperatures may be very similar in the two kinds of timberlines. A series of warm summers in the 1940s seems to have permitted the establishment of “significant numbers” of spruce seedlings above the treeline in the hills near Fairbanks. Survival depends on a sufficiency of new growth to support the tree, the windiness of high-elevation sites is also a potent determinant of the distribution of tree growth. However, snow accumulation in sheltered gullies in the Selkirk Mountains of southeastern British Columbia causes timberline to be 400 metres lower than on exposed intervening shoulders. In a desert, the line marks the driest places where trees can grow. These tend to be called the tree line and occur below about 5,000 ft elevation in the Desert Southwestern United States. In some mountainous areas, higher elevations above the line or on equator-facing and leeward slopes can result in low rainfall. This dries out the soil, resulting in an arid environment unsuitable for trees
8.
Donkey
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The donkey or ass is a domesticated member of the horse family, Equidae. The wild ancestor of the donkey is the African wild ass, the donkey has been used as a working animal for at least 5000 years. There are more than 40 million donkeys in the world, mostly in underdeveloped countries, working donkeys are often associated with those living at or below subsistence levels. Small numbers of donkeys are kept for breeding or as pets in developed countries, a male donkey or ass is called a jack, a female a jenny or jennet, a young donkey is a foal. Jack donkeys are used to mate with female horses to produce mules. Asses were first domesticated around 3000 BC, probably in Egypt or Mesopotamia and they continue to fill important roles in many places today. While domesticated species are increasing in numbers, the African wild ass is an endangered species, as beasts of burden and companions, asses and donkeys have worked together with humans for millennia. Traditionally, the name for the donkey is Equus asinus asinus based on the principle of priority used for scientific names of animals. This means that the scientific name for the donkey is Equus africanus asinus when it is considered a subspecies. At one time, the ass was the more common term for the donkey. The first recorded use of donkey was in either 1784 or 1785, while the word ass has cognates in most other Indo-European languages, donkey is an etymologically obscure word for which no credible cognate has been identified. From the 18th century, donkey gradually replaced ass, and jenny replaced she-ass, by the end of the 17th century, changes in pronunciation of both ass and arse had caused them to become homophones. Donkeys vary considerably in size, depending on breed and management, the height at the withers ranges from 7.3 to 15.3 hands, and the weight from 80 to 480 kg. Working donkeys in the poorest countries have an expectancy of 12 to 15 years, in more prosperous countries. Donkeys are adapted to desert lands. Unlike wild and feral horses, wild donkeys in dry areas are solitary, each adult donkey establishes a home range, breeding over a large area may be dominated by one jack. Donkeys have large ears, which may pick up more distant sounds, donkeys can defend themselves by biting, striking with the front hooves or kicking with the hind legs. A jenny is normally pregnant for about 12 months, though the period varies from 11 to 14 months
9.
1938 New England hurricane
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The 1938 New England Hurricane was one of the deadliest and most destructive tropical cyclones to impact New England. The hurricane was estimated to have killed 682 people, damaged or destroyed over 57,000 homes, even as late as 1951, damaged trees and buildings were still seen in the affected areas. It remains the most powerful and deadliest hurricane in recent New England history and it was only the third hurricane to strike New England since 1635. The storm was first analyzed by ship south of the Cape Verde Islands on September 9. Over the next ten days, it gathered strength and slowly tracked to the west-northwest. By September 20, while centered east of the Bahamas, the hurricane is estimated to have reached Category 5 intensity, in response to a deep trough over Appalachia, the hurricane veered northward, sparing the Bahamas, Florida, the Carolinas, and the Mid-Atlantic. At the same time, a pressure system was centered north of Bermuda. Thus, the hurricane was effectively squeezed to the north between the two weather systems, late on September 20, this set-up caused the storms forward speed to increase substantially, ultimately reaching 70 mph, the highest forward velocity ever recorded in the annals of hurricanes. During the early hours of September 21, the storm, centered several hundred miles to the southeast of Cape Hatteras, weakened slightly. By 8,30 am EDT, the hurricane was centered approximately 100 miles due east of Cape Hatteras and this rapid movement did not give the hurricane a sufficient amount of time to weaken over the cooler waters before it reached Long Island. During the 9,00 am EDT hour, the hurricane sped through the Virginia tidewater, between 12,00 pm and 2,00 pm EDT, the New Jersey coastline and New York City caught the western edge of the hurricane. At the same time, weather conditions began to deteriorate rapidly on Long Island as well as along the southern New England coast. The hurricane made landfall at Bellport on Long Islands Suffolk County sometime between 2,10 pm and 2,40 pm EDT as a category 3 hurricane with sustained winds of 120 mph. The storm made a second landfall still as a category 3 hurricane somewhere between Bridgeport and New Haven, Connecticut, around 4,00 pm with sustained winds of 115 mph. By 5,00 pm EDT, the eye moved into western Massachusetts, and by 6,00 pm EDT, the hurricane reached Vermont. Both Westfield, Massachusetts, and Dorset, Vermont, reported calm conditions and partial clearing during passage of the eye, as the hurricane continued into northern Vermont, it began to lose tropical characteristics. Still carrying hurricane-force winds, the crossed into Quebec at approximately 10,00 pm EDT. The post-tropical remnants dissipated over northern Ontario a few days later, in 1938 United States forecasting lagged behind forecasting in Europe, where new techniques of analyzing air masses and taking into account the influence of fronts were being used
10.
Americans with Disabilities Act of 1990
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The Americans with Disabilities Act of 1990 is a US labor law that prohibits unjustified discrimination based on disability. The final version of the bill was signed into law on July 26,1990 and it was later amended in 2008 and signed by President George W. Bush with changes effective as of January 1,2009. ADA disabilities include both mental and physical medical conditions, a condition does not need to be severe or permanent to be a disability. Additionally, other conditions, such as gender identity disorders, are also excluded under the definition of disability. The ADA states that an entity shall not discriminate against a qualified individual with a disability. This applies to job application procedures, hiring, advancement and discharge of employees, job training, and other terms, conditions, covered entities include employers with 15 or more employees, as well as employment agencies, labor organizations, and joint labor-management committees. Prohibited discrimination may include, among other things, firing or refusing to hire someone based on a real or perceived disability, segregation, covered entities are also required to provide reasonable accommodations to job applicants and employees with disabilities. An employee or applicant who currently engages in the use of drugs is not considered qualified when a covered entity takes adverse action based on such use. There are many ways to discriminate against people based on disabilities, anyone known to have a history of mental disorders can be considered disabled. Employers with more than 15 employees must take care to all employees fairly. Even when an employee is doing a job well, she or he is not necessarily no longer disabled. The Court determined that state employees cannot sue their employer for violating ADA rules, state employees can, however, file complaints at the Department of Justice or the Equal Employment Opportunity Commission, who can sue on their behalf. Title II prohibits disability discrimination by all entities at the local level, e. g. school district, municipal, city, or county. Public entities must comply with Title II regulations by the U. S. Department of Justice and these regulations cover access to all programs and services offered by the entity. Access includes physical access described in the ADA Standards for Accessible Design, Title II applies to public transportation provided by public entities through regulations by the U. S. Department of Transportation. It includes the National Railroad Passenger Corporation, along all other commuter authorities. This section requires the provision of services by public entities that provide fixed route services. ADA also sets minimum requirements for space layout in order to facilitate wheelchair securement on public transport, Title II also applies to all state and local public housing, housing assistance, and housing referrals
11.
Composting toilet
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A composting toilet is a type of dry toilet or micro-flush toilet system that uses a predominantly aerobic process to treat human excreta by composting or managed aerobic decomposition. These toilets generally use little to no water and may be used as an alternative to flush toilets that are coupled with septic systems or city sewer systems and they have found use in situations where no suitable water supply or sewer system and sewage treatment plant is available. They are in use in many facilities and national parks in Sweden, Canada, US, UK. They are used in holiday homes in Sweden and Finland. The human excreta is usually mixed with sawdust, coconut coir or peat moss to facilitate processing, liquid absorption. Most composting toilets use slow, cold composting conditions, sometimes connected to a secondary external composting step, Composting toilets produce a compost that may be used for horticultural or agricultural soil enrichment if the local regulations allow this. A secondary stage is often needed to allow mesophilic composting to further reduce potential pathogens, the term composting toilet is used quite loosely, and its meaning may vary by country. For example, in English-speaking countries, the term composting is used. In Germany and Scandinavian countries, composting always refers to an aerobic process. This aerobic composting may take place with an increase in temperature due to microbial action, if earth worms are used then there is also no increase in temperature. They also differ from urine-diverting dry toilets where pathogen reduction is achieved through dehydration, Composting toilets target a certain degree of moisture in the composting chamber. Composting toilets usually do not divert urine, offering a waterless urinal in addition to the toilet can help keep excess amounts of urine out of the composting chamber. Composting toilets can be used to implement an ecological sanitation approach for resource recovery, however, this is not recommended as the two terms are not identical. Composting toilets have also been called sawdust toilets, which can be if the amount of aerobic composting taking place in the toilets container is very limited. The Clivus multrum is a type of composting toilet which has a large composting chamber below the toilet seat, Composting toilets can be suitable in areas such as a rural area or a park that lacks a suitable water supply, sewers and sewage treatment. They can also increase the resilience of existing sanitation systems in the face of possible natural disasters such as climate change. Composting toilets can reduce or perhaps eliminate the need for a tank system to reduce environmental footprint. These types of toilets can be used for recovery by reusing sanitized feces and urine as fertilizer
12.
Rebar
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Rebars surface is often patterned to form a better bond with the concrete. Rebar has been used in construction since at least the 15th century, more recently, during the 18th century, rebar was used to form the carcass of the Leaning Tower of Nevyansk in Russia, built on the orders of the industrialist Akinfiy Demidov. The cast iron used for the rebar was of high quality, the carcass of the tower was connected to its cast iron tented roof, crowned with one of the first known lightning rods. More recently these techniques have been refined by embedding the steel bars in the concrete, concrete is a material that is very strong in compression, but relatively weak in tension. To compensate for this imbalance in concretes behavior, rebar is cast into it to carry the tensile loads, rebar is also employed to confer resistance to concentrated loads by providing enough localized resistance and stiffness for a load to spread through a wider area. Rebar may also be used to other steel bars in the correct position to accommodate their loads. External steel tie bars can constrain and reinforce masonry structures, as illustrated by the Nevyansk Tower or ancient structures in Rome, masonry structures and the mortar holding them together have similar properties to concrete and also have a limited ability to carry tensile loads. Some standard masonry units like blocks and bricks are made with voids to accommodate rebar and this combination is known as reinforced masonry. Steel has a thermal expansion coefficient nearly equal to that of modern concrete, if this were not so, it would cause problems through additional longitudinal and perpendicular stresses at temperatures different from the temperature of the setting. To prevent such a failure, rebar is either deeply embedded into adjacent structural members, or bent and hooked at the ends to lock it around the concrete and other rebar. This first approach increases the friction locking the bar into place, common rebar is made of unfinished tempered steel, making it susceptible to rusting. Normally the concrete cover is able to provide a pH value higher than 12 avoiding the corrosion reaction, too little concrete cover can compromise this guard through carbonation from the surface, and salt penetration. Too much concrete cover can cause bigger crack widths which also compromises the local guard and this phenomenon is known as oxide jacking. This is a problem where the concrete is exposed to salt water, as in bridges where salt is applied to roadways in winter. Even damaged bars have shown better performance than uncoated reinforcing bars, though issues from debonding of the coating from the bars. These bars are used in over 70,000 bridge decks in the USA, fiber-reinforced polymer rebar is also used in high-corrosion environments. It is available in forms, such as spirals for reinforcing columns, common rods. Most commercially available rebar is made from glass fibre reinforced thermoset resins
