Snow removal or snow clearing is the job of removing snow after a snowfall to make travel easier and safer. This is done by governments and institutions. De-icing is defined as removal of existing snow, ice or frost from a roadway, airport runway, or other surface, it includes both mechanical means, such as plowing or scraping, chemical means, such as application of salt or other ice-melting chemicals. Anti-icing is treatment with ice-melting chemicals before or during the onset of a storm in order to prevent or delay the formation and adhesion of ice and snow to the surface. Brine, or wetted salt, is applied shortly before the beginning of a snowstorm; when properly performed, anti-icing can reduce the amount of salt required and allow easier removal by mechanical methods, including plowing. The de-icing of roads has been accomplished by snowplows or specially-designed dump trucks that spread salt mixed with sand and gravel, onto slick roads. Rock salt is used because it is inexpensive and available in large quantities.
However, brine freezes at −18 °C, so it is ineffective at these low temperatures. It has a strong tendency to cause corrosion, rusting the steel used in most vehicles and the rebar in concrete bridges. More recent snowmelters use other salts, such as calcium chloride and magnesium chloride, which not only decrease the freezing point of water to a much lower temperature but produce an exothermic reaction, whose dissipated heat further aids in melting. In addition, they are somewhat safer for concrete sidewalks. Organic compounds have been developed that reduce the environmental impact associated with salts and that have longer residual effects when spread on roadways in conjunction with salt brines or solids; these compounds are generated as byproducts of agricultural operations, such as sugar beet refining or ethanol distillation. A mixture of some selection of these organic compounds with a combination of salts results in a substance, both more spread and more effective at lower temperatures.
Since the 1990s, use of liquid chemical melters has been increasing, sprayed on roads by nozzles instead of a spinning spreader used with salts. Liquid melters are more effective at preventing the ice from bonding to the surface than melting through existing ice. Several proprietary products incorporate anti-icing chemicals into the pavement. Verglimit incorporates calcium chloride granules into asphalt pavement; the granules are continually exposed by traffic wear, release calcium chloride onto the surface. This prevents snow and ice from sticking to the pavement Cargill SafeLane is a proprietary pavement surface treatment that absorbs anti-icing brines, to be released during a storm or other icing event, it provides a high-friction surface, increasing traction. In Niigata, Japan inexpensive hot water bubbles up through holes in the pavement to melt snow, though this solution is only practical within a city or town; some individual buildings may melt snow and ice with electric heating elements buried in the pavement, or on a roof to prevent ice dams on the shingles, or to keep massive chunks of snow and dangerous icicles from collapsing on anyone below.
Small areas of pavement can be kept ice-free by circulating heated liquids in embedded piping systems. Most snow removal by individuals is clearance of walkways. After heavy snowfalls, snow may be removed from roofs to reduce the risk of structural damage due to the weight. In places with light snow, brooms or other light instruments can be used to brush off snow from walks and other surfaces. In regions with more precipitation, snow is removed with snow shovels, a large lightweight shovel used to push snow and lift it, snow scoops or sleigh shovels, a large and deep hopper-like implement fitted with a wide handle and designed to scoop up a load of snow and slide it on any slippery surface to another location without lifting. Other tools include snow shovels with one or more wheels. Shovelling can strain the back and the heart; each year middle aged persons die from heart attacks while shovelling snow. Snow blowers are used by people unwilling or unable to perform this labour, people with large driveways or other substantial surfaces and people who live in areas with long lasting winters with large amounts of snowfall.
Others may hire a contractor with a shovel. After a large snowfall, businessmen with plow trucks drive through cities offering to plow for money. Removing ice is more difficult. Snow blowers are ineffective at clearing ice. Picks are sometimes used. There is always the risk of damaging the pavement with these instruments. Icy areas can be covered with salt or some other substance, bags of which are available. A recent technological advance is the snowmelt system that heats the pavement from below and melts snow and ice after a period of time; such systems are expensive to install and operate and they are not cost effective in areas with low winter temperatures and large snowfalls. Some governments offer free snow clearing for the elderly and others in need. In some cities, snow clearing for elder and handicapped residents counts towards community service hours assigned as a punishment for minor offences. In some places, laws require homeowners to clear snow from the public sidewalk in front of their house, as well as a pathway on their own property to their mailbox.
Those who fail to do so, depending on the jurisdiction's laws, may experience fines and may be civilly liable fo
British Columbia is the westernmost province of Canada, located between the Pacific Ocean and the Rocky Mountains. With an estimated population of 5.016 million as of 2018, it is Canada's third-most populous province. The first British settlement in the area was Fort Victoria, established in 1843, which gave rise to the City of Victoria, at first the capital of the separate Colony of Vancouver Island. Subsequently, on the mainland, the Colony of British Columbia was founded by Richard Clement Moody and the Royal Engineers, Columbia Detachment, in response to the Fraser Canyon Gold Rush. Moody was Chief Commissioner of Lands and Works for the Colony and the first Lieutenant Governor of British Columbia: he was hand-picked by the Colonial Office in London to transform British Columbia into the British Empire's "bulwark in the farthest west", "to found a second England on the shores of the Pacific". Moody selected the site for and founded the original capital of British Columbia, New Westminster, established the Cariboo Road and Stanley Park, designed the first version of the Coat of arms of British Columbia.
Port Moody is named after him. In 1866, Vancouver Island became part of the colony of British Columbia, Victoria became the united colony's capital. In 1871, British Columbia became the sixth province of Canada, its Latin motto is Splendor sine occasu. The capital of British Columbia remains Victoria, the fifteenth-largest metropolitan region in Canada, named for Queen Victoria, who ruled during the creation of the original colonies; the largest city is Vancouver, the third-largest metropolitan area in Canada, the largest in Western Canada, the second-largest in the Pacific Northwest. In October 2013, British Columbia had an estimated population of 4,606,371; the province is governed by the British Columbia New Democratic Party, led by John Horgan, in a minority government with the confidence and supply of the Green Party of British Columbia. Horgan became premier as a result of a no-confidence motion on June 29, 2017. British Columbia evolved from British possessions that were established in what is now British Columbia by 1871.
First Nations, the original inhabitants of the land, have a history of at least 10,000 years in the area. Today there are few treaties, the question of Aboriginal Title, long ignored, has become a legal and political question of frequent debate as a result of recent court actions. Notably, the Tsilhqot'in Nation has established Aboriginal title to a portion of their territory, as a result of the 2014 Supreme Court of Canada decision in Tsilhqot'in Nation v British Columbia; the province's name was chosen by Queen Victoria, when the Colony of British Columbia, i.e. "the Mainland", became a British colony in 1858. It refers to the Columbia District, the British name for the territory drained by the Columbia River, in southeastern British Columbia, the namesake of the pre-Oregon Treaty Columbia Department of the Hudson's Bay Company. Queen Victoria chose British Columbia to distinguish what was the British sector of the Columbia District from the United States, which became the Oregon Territory on August 8, 1848, as a result of the treaty.
The Columbia in the name British Columbia is derived from the name of the Columbia Rediviva, an American ship which lent its name to the Columbia River and the wider region. British Columbia is bordered to the west by the Pacific Ocean and the American state of Alaska, to the north by Yukon Territory and the Northwest Territories, to the east by the province of Alberta, to the south by the American states of Washington and Montana; the southern border of British Columbia was established by the 1846 Oregon Treaty, although its history is tied with lands as far south as California. British Columbia's land area is 944,735 square kilometres. British Columbia's rugged coastline stretches for more than 27,000 kilometres, includes deep, mountainous fjords and about 6,000 islands, most of which are uninhabited, it is the only province in Canada. British Columbia's capital is Victoria, located at the southeastern tip of Vancouver Island. Only a narrow strip of Vancouver Island, from Campbell River to Victoria, is populated.
Much of the western part of Vancouver Island and the rest of the coast is covered by temperate rainforest. The province's most populous city is Vancouver, at the confluence of the Fraser River and Georgia Strait, in the mainland's southwest corner. By land area, Abbotsford is the largest city. Vanderhoof is near the geographic centre of the province; the Coast Mountains and the Inside Passage's many inlets provide some of British Columbia's renowned and spectacular scenery, which forms the backdrop and context for a growing outdoor adventure and ecotourism industry. 75% of the province is mountainous. The province's mainland away from the coastal regions is somewhat moderated by the Pacific Ocean. Terrain ranges from dry inland forests and semi-arid valleys, to the range and canyon districts of the Central and Southern Interior, to boreal forest and subarctic prairie in the Northern Interior. High mountain regions both north and south subalpine climate; the Okanagan area, extending from Vernon to Osoyoos at the United States border, is one of several wine and cider-produci
Erythronium is a genus of Eurasian and North American plants in the lily family, most related to tulips. The name Erythronium derives from Ancient Greek ἐρυθρός "red" in Greek, referring to the red flowers of E. dens-canis. Erythronium includes about 20–30 species of hardy spring-flowering perennial plants with long, tooth-like bulbs. Slender stems carry pendent flowers with recurved tepals in shades of cream, yellow and mauve. Species are native to meadows in temperate regions of the Northern Hemisphere. Photos Two species names were coined using the name Erythronium but have since been reclassified to other taxa. Erythronium carolinianum, now called Uvularia perfoliata Erythronium hyacinthoides, now called Drimia indica The bulb is edible as a root vegetable, cooked or dried, can be ground into flour; the leaves can be cooked as a leaf vegetable. In Japan, Erythronium japonicum is called katakuri, the bulb is processed to produce starch, used for food and other purposes, they are widely grown as ornamental plants, with numerous hybrids and cultivars having been selected for garden use.
Popular cultivars include Erythronium'Pagoda', E.'Sundisc', E.'Joanna', E.'Kondo', E.'Citronella', E. californicum'White Beauty', E.'Rosalind'. Propagation is best by division of bulbs, depending on species; some species propagate vegetatively. The plant is great as a ground cover, as it will spread over several years
San Juan Mountains
The San Juan Mountains are a high and rugged mountain range in the Rocky Mountains in southwestern Colorado and northwestern New Mexico. The area is mineralized and figured in the gold and silver mining industry of early Colorado. Major towns, all old mining camps, include Creede, Lake City, Silverton and Telluride. Large scale mining has ended in the region, although independent prospectors still work claims throughout the range; the last large scale mines were the Sunnyside Mine near Silverton, which operated until late in the 20th century and the Idarado Mine on Red Mountain Pass that closed down in the 1970s. Famous old San Juan mines include the Camp Bird and Smuggler Union mines, both located between Telluride and Ouray; the Summitville mine was the scene of a major environmental disaster in the 1990s when the liner of a cyanide-laced tailing pond began leaking heavily. Summitville is in the Summitville caldera, one of many extinct volcanoes making up the San Juan volcanic field. One, La Garita Caldera, is 35 miles in diameter.
Large beds of lava, some extending under the floor of the San Luis Valley, are characteristic of the eastern slope of the San Juans. Tourism is now a major part of the regional economy, with the narrow gauge railway between Durango and Silverton being an attraction in the summer. Jeeping is popular on the old trails which linked the historic mining camps, including the notorious Black Bear Road. Visiting old ghost towns is popular, as is wilderness trekking and mountain climbing. Many of the old mining camps are now popular sites of summer homes. Though the San Juans are steep and receive a lot of snow, so far only Telluride has made the transition to a major ski resort. Purgatory Resort, once known as Durango Mountain Resort, is a small ski area 26 miles north of Durango. There is skiing on Wolf Creek Pass at the Wolf Creek ski area. Silverton Mountain ski area has begun operation near Silverton; the Rio Grande drains the east side of the range. The other side of the San Juans, the western slope of the continental divide, is drained by tributaries of the San Juan and Gunnison rivers, which all flow into the Colorado River.
The San Juan and Uncompahgre National Forests cover a large portion of the San Juan Mountains. The San Juan Mountains are distinctive for their high altitude plateaus and peaks; as a result, facilities in the towns and cities of the region are among the highest in the nation. Telluride Airport, at an elevation of 9,070 feet, is the highest in the United States with scheduled commercial service. Note: This is only a partial list of important peaks in the San Juans, listing peaks by prominence only. There are dozens more summits over 12,000 feet. Mining operators in the San Juan mountain area formed the San Juan District Mining Association in 1903, as a direct result of a Western Federation of Miners proposal to the Telluride Mining Association for the eight-hour day, approved in a referendum by 72 percent of Colorado voters; the new association consolidated the power of thirty-six mining properties in San Miguel and San Juan counties. The SJDMA refused to consider any reduction in hours or increase in wages, helping to provoke a bitter strike.
Southern Rocky Mountains Sneffels Range Cimmaron Range Needle Mountains La Garita Mountains Cochetopa Hills La Plata Mountains Mountain ranges of Colorado Bove, D. et al.. Geochronology and geology of Late Oligocene through Miocene volcanism and mineralization in the western San Juan Mountains, Colorado. Washington, D. C.: U. S. Department of the Interior, U. S. Geological Survey. Lippman, P. W.. Geologic map of southwestern Colorado. Reston, VA: U. S. Department of the Interior, U. S. Geological Survey. Widerange.org: Photos of the San Juan Mountains San Juan Mountains @ Peakbagger Southern Rocky Mountains @ Peakbagger Rocky Mountains @ Peakbagger
Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared and ultraviolet light. On Earth, sunlight is filtered through Earth's atmosphere, is obvious as daylight when the Sun is above the horizon; when the direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat. When it is blocked by clouds or reflects off other objects, it is experienced as diffused light; the World Meteorological Organization uses the term "sunshine duration" to mean the cumulative time during which an area receives direct irradiance from the Sun of at least 120 watts per square meter. Other sources indicate an "Average over the entire earth" of "164 Watts per square meter over a 24 hour day"; the ultraviolet radiation in sunlight has both positive and negative health effects, as it is both a requisite for vitamin D3 synthesis and a mutagen. Sunlight takes about 8.3 minutes to reach Earth from the surface of the Sun.
A photon starting at the center of the Sun and changing direction every time it encounters a charged particle would take between 10,000 and 170,000 years to get to the surface. Sunlight is a key factor in photosynthesis, the process used by plants and other autotrophic organisms to convert light energy from the Sun, into chemical energy that can be used to synthesize carbohydrates and to fuel the organisms' activities. Researchers can measure the intensity of sunlight using a sunshine recorder, pyranometer, or pyrheliometer. To calculate the amount of sunlight reaching the ground, both the eccentricity of Earth's elliptic orbit and the attenuation by Earth's atmosphere have to be taken into account; the extraterrestrial solar illuminance, corrected for the elliptic orbit by using the day number of the year, is given to a good approximation by E e x t = E s c ⋅, where dn=1 on January 1st. In this formula dn–3 is used, because in modern times Earth's perihelion, the closest approach to the Sun and, the maximum Eext occurs around January 3 each year.
The value of 0.033412 is determined knowing that the ratio between the perihelion squared and the aphelion squared should be 0.935338. The solar illuminance constant, is equal to 128×103 lux; the direct normal illuminance, corrected for the attenuating effects of the atmosphere is given by: E d n = E e x t e − c m, where c is the atmospheric extinction and m is the relative optical airmass. The atmospheric extinction brings the number of lux down to around 100 000 lux; the total amount of energy received at ground level from the Sun at the zenith depends on the distance to the Sun and thus on the time of year. It is 3.3 % lower in July. If the extraterrestrial solar radiation is 1367 watts per square meter the direct sunlight at Earth's surface when the Sun is at the zenith is about 1050 W/m2, but the total amount hitting the ground is around 1120 W/m2. In terms of energy, sunlight at Earth's surface is around 52 to 55 percent infrared, 42 to 43 percent visible, 3 to 5 percent ultraviolet. At the top of the atmosphere, sunlight is about 30% more intense, having about 8% ultraviolet, with most of the extra UV consisting of biologically damaging short-wave ultraviolet.
Direct sunlight has a luminous efficacy of about 93 lumens per watt of radiant flux. Multiplying the figure of 1050 watts per square metre by 93 lumens per watt indicates that bright sunlight provides an illuminance of 98 000 lux on a perpendicular surface at sea level; the illumination of a horizontal surface will be less than this if the Sun is not high in the sky. Averaged over a day, the highest amount of sunlight on a horizontal surface occurs in January at the South Pole. Dividing the irradiance of 1050 W/m2 by the size of the Sun's disk in steradians gives an average radiance of 15.4 MW per square metre per steradian. Multiplying this by π gives an upper limit to the irradiance which can be focused on a surface using mirrors: 48.5 MW/m2. The spectrum of the Sun's solar radiation is close to that of a black body with a temperature of about 5,800 K; the Sun emits EM radiation across most of the electromagnetic spectrum. Although the Sun produces gamma rays as a result of the nuclear-fusion process, internal absorption and thermalization convert these super-high-energy photons to lower-energy photons before they reach the Sun's surface and are emitted out into space.
As a result, the Sun does not emit gamma rays from this process, but it does emit gamma rays from solar flares. The Sun emits X-rays, vis
Atmosphere of Earth
The atmosphere of Earth is the layer of gases known as air, that surrounds the planet Earth and is retained by Earth's gravity. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention, reducing temperature extremes between day and night. By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, small amounts of other gases. Air contains a variable amount of water vapor, on average around 1% at sea level, 0.4% over the entire atmosphere. Air content and atmospheric pressure vary at different layers, air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in Earth's troposphere and in artificial atmospheres; the atmosphere has a mass of about 5.15×1018 kg, three quarters of, within about 11 km of the surface. The atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space.
The Kármán line, at 100 km, or 1.57% of Earth's radius, is used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km. Several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition; the study of Earth's atmosphere and its processes is called atmospheric science. Early pioneers in the field include Richard Assmann; the three major constituents of Earth's atmosphere are nitrogen and argon. Water vapor accounts for 0.25% of the atmosphere by mass. The concentration of water vapor varies from around 10 ppm by volume in the coldest portions of the atmosphere to as much as 5% by volume in hot, humid air masses, concentrations of other atmospheric gases are quoted in terms of dry air; the remaining gases are referred to as trace gases, among which are the greenhouse gases, principally carbon dioxide, nitrous oxide, ozone. Filtered air includes trace amounts of many other chemical compounds.
Many substances of natural origin may be present in locally and seasonally variable small amounts as aerosols in an unfiltered air sample, including dust of mineral and organic composition and spores, sea spray, volcanic ash. Various industrial pollutants may be present as gases or aerosols, such as chlorine, fluorine compounds and elemental mercury vapor. Sulfur compounds such as hydrogen sulfide and sulfur dioxide may be derived from natural sources or from industrial air pollution; the relative concentration of gases remains constant until about 10,000 m. In general, air pressure and density decrease with altitude in the atmosphere. However, temperature has a more complicated profile with altitude, may remain constant or increase with altitude in some regions; because the general pattern of the temperature/altitude profile is constant and measurable by means of instrumented balloon soundings, the temperature behavior provides a useful metric to distinguish atmospheric layers. In this way, Earth's atmosphere can be divided into five main layers.
Excluding the exosphere, the atmosphere has four primary layers, which are the troposphere, stratosphere and thermosphere. From highest to lowest, the five main layers are: Exosphere: 700 to 10,000 km Thermosphere: 80 to 700 km Mesosphere: 50 to 80 km Stratosphere: 12 to 50 km Troposphere: 0 to 12 km The exosphere is the outermost layer of Earth's atmosphere, it extends from the exobase, located at the top of the thermosphere at an altitude of about 700 km above sea level, to about 10,000 km where it merges into the solar wind. This layer is composed of low densities of hydrogen and several heavier molecules including nitrogen and carbon dioxide closer to the exobase; the atoms and molecules are so far apart that they can travel hundreds of kilometers without colliding with one another. Thus, the exosphere no longer behaves like a gas, the particles escape into space; these free-moving particles follow ballistic trajectories and may migrate in and out of the magnetosphere or the solar wind. The exosphere is located too far above Earth for any meteorological phenomena to be possible.
However, the aurora borealis and aurora australis sometimes occur in the lower part of the exosphere, where they overlap into the thermosphere. The exosphere contains most of the satellites orbiting Earth; the thermosphere is the second-highest layer of Earth's atmosphere. It extends from the mesopause at an altitude of about 80 km up to the thermopause at an altitude range of 500–1000 km; the height of the thermopause varies due to changes in solar activity. Because the thermopause lies at the lower boundary of the exosphere, it is referred to as the exobase; the lower part of the thermosphere, from 80 to 550 kilometres above Earth's surface, contains the ionosphere. The temperature of the thermosphere increases with height. Unlike the stratosphere beneath it, wherein a temperature inversion is due to the absorption of radiation by ozone, the inversion in the t