North American porcupine
The North American porcupine known as the Canadian porcupine or common porcupine, is a large rodent in the New World porcupine family. The beaver is the only rodent in North America, larger than the North American porcupine; the porcupine is a caviomorph rodent whose ancestors rafted across the Atlantic from Africa to Brazil over 30 million years ago, migrated to North America during the Great American Interchange after the Isthmus of Panama rose 3 million years ago. The word "porcupine" comes from the old French word porcespin, which means thorn pig, its roots derive from pig and spina meaning thorns. Other colloquial names for the animal include quill pig, it is referred to as the Canadian porcupine or common porcupine. The porcupine's scientific name, Erethizon dorsatum, can be loosely translated as "the animal with the irritating back". Several Native American names exist, such as the Lakota name pahin meaning quill and the Chipewyan name ts'l; the North American porcupine migrated from South America, where all New World porcupines or hystricomorphs evolved.
Erethizon appeared in North America shortly after the two continents joined together in the Tertiary period. Other hystricomorphs migrated, but Erethizon was the only one to survive north of Mexico. No known fossils are attributed to hystricomorphs prior to the late Tertiary period; some fossils, such as species from the family Paramyidae, show resemblance to the porcupine, but they are so primitive and generalized that they could be ancestors to all rodents. South American hystricomorphs first appeared in the Lower Oligocene period, they are thought to have migrated from Africa, ancestors of the Old World porcupines or Hystricidae or they originated based on a migration of the North American Paramyidae. The earliest appearance of E. dorsatum is from the Pleistocene era found along the Arroyo del Cedazo near Aguascalientes, Mexico. Seven subspecies of E. dorsatum are recognized. They are subdivided by different ranges across North America. By far the most common is E. d. dorsatum, which ranges from Nova Scotia to Alberta and from Virginia to the Yukon.
E. d. picinum occupies a small range in northeastern Labrador. E. d. couesi is the most southern ranging from northern Mexico to Colorado. E. d. bruneri can be found in the midwest from Arkansas to Montana. The last three are found in the west. From south to north they are E.d. epixanthum, E. d. nigrescens, E. d. myops. Porcupines are dark brown or black in color, with white highlights, they have a stocky body, a small face, short legs, a short, thick tail. This species is the largest of the New World porcupines and is one of the largest North American rodents, second only to the American beaver in size; the head-and-body length is 60 to 90 cm. The hind foot length is 7.5 to 9.1 cm. Weight can range from 3.5 to 18 kg. Weight in adult females can average some 7 kg; the porcupine is the only native North American mammal with antibiotics in its skin. Those antibiotics prevent infection when a porcupine falls out of a tree and is stuck with its own quills upon hitting the ground. Porcupines fall out of trees often because they are tempted by the succulent buds and twigs at the ends of the branches.
The porcupine and the skunk are the only North American mammals that have black and white colors because they are the only mammals that benefit from letting other animals know where and what they are in the dark of the night. The most distinguishing feature of the porcupine is its coat of quills. An adult porcupine has about 30,000 quills that cover all of its body except its underbelly and feet. Quills are modified hairs formed into sharp, hollow spines, they are used for defense, but serve to insulate their bodies during winter. Porcupines do not throw their quills, but when threatened, they contract the muscles near the skin which causes the quills to stand up and out from their bodies; when the quills are in this position, they become easier to detach from the body when the porcupines swing their tails towards attackers. The barbs at the tip become lodged in the flesh of an attacker and are difficult and painful to remove; the quills are flattened against the body and in this position are less dislodged.
The North American porcupine has a strong odor to warn away predators, which it can increase when agitated. The smell has been described as similar to goats, or some cheeses; the odor is generated by a patch of skin called the rosette, on the lower back where modified quills serve as osmetrichia to broadcast the smell. The characteristic odor comes from the R-enantiomer of delta-decalactone. Not present is the S-enantiomer, used in flavorings and perfumes. North American porcupines range from Canada and into northern Mexico, they are found in coniferous and mixed forested areas, but have adapted to harsh environments such as shrublands and deserts. They make their dens in rocky areas. During the summer, they eat twigs, stems and other vegetation. In the winter, they eat conifer needles and tree bark. Porcupines are selective in their eating. Porcupines are slow-moving, they are active at night. They do not sleep in and stay close to their dens in winter; the strength
Forestry is the science and craft of creating, using and repairing forests and associated resources for human and environmental benefits. Forestry is practiced in natural stands; the science of forestry has elements that belong to the biological, social and managerial sciences. Modern forestry embraces a broad range of concerns, in what is known as multiple-use management, including the provision of timber, fuel wood, wildlife habitat, natural water quality management, recreation and community protection, aesthetically appealing landscapes, biodiversity management, watershed management, erosion control, preserving forests as "sinks" for atmospheric carbon dioxide. A practitioner of forestry is known as a forester. Other common terms are: a silviculturalist. Silviculture is narrower than forestry, being concerned only with forest plants, but is used synonymously with forestry. Forest ecosystems have come to be seen as the most important component of the biosphere, forestry has emerged as a vital applied science and technology.
Forestry is an important economic segment in various industrial countries. For example, in Germany, forests cover nearly a third of the land area, wood is the most important renewable resource, forestry supports more than a million jobs and about €181 billion of value to the German economy each year; the preindustrial age has been dubbed by Werner Sombart and others as the'wooden age', as timber and firewood were the basic resources for energy and housing. The development of modern forestry is connected with the rise of capitalism, economy as a science and varying notions of land use and property. Roman Latifundiae, large agricultural estates, were quite successful in maintaining the large supply of wood, necessary for the Roman Empire. Large deforestations came with after the decline of the Romans; however in the 5th century, monks in the Byzantine Romagna on the Adriatic coast, were able to establish stone pine plantations to provide fuelwood and food. This was the beginning of the massive forest mentioned by Dante Alighieri in his 1308 poem Divine Comedy.
Similar sustainable formal forestry practices were developed by the Visigoths in the 7th century when, faced with the ever-increasing shortage of wood, they instituted a code concerned with the preservation of oak and pine forests. The use and management of many forest resources has a long history in China as well, dating back to the Han dynasty and taking place under the landowning gentry. A similar approach was used in Japan, it was later written about by the Ming dynasty Chinese scholar Xu Guangqi. In Europe, land usage rights in medieval and early modern times allowed different users to access forests and pastures. Plant litter and resin extraction were important, as pitch was essential for the caulking of ships and hunting rights and building, timber gathering in wood pastures, for grazing animals in forests; the notion of "commons" refers to the underlying traditional legal term of common land. The idea of enclosed private property came about during modern times. However, most hunting rights were retained by members of the nobility which preserved the right of the nobility to access and use common land for recreation, like fox hunting.
Systematic management of forests for a sustainable yield of timber began in Portugal in the 13th century when Afonso III of Portugal planted the Pinhal do Rei near Leiria to prevent coastal erosion and soil degradation, as a sustainable source for timber used in naval construction. His successor Dom Dinis continued the forest exists still today. Forest management flourished in the German states in the 14th century, e.g. in Nuremberg, in 16th-century Japan. A forest was divided into specific sections and mapped; as timber rafting allowed for connecting large continental forests, as in south western Germany, via Main, Neckar and Rhine with the coastal cities and states, early modern forestry and remote trading were connected. Large firs in the black forest were called "Holländer ``. Large timber rafts on the Rhine were 200 to 400m in length, 40m in width and consisted of several thousand logs; the crew consisted of 400 to 500 men, including shelter, bakeries and livestock stables. Timber rafting infrastructure allowed for large interconnected networks all over continental Europe and is still of importance in Finland.
Starting with the sixteenth century, enhanced world maritime trade, a boom in housing construction in Europe and the success and further Berggeschrey of the mining industry increased timber consumption sharply. The notion of'Nachhaltigkeit', sustainability in forestry, is connected to the work of Hans Carl von Carlowitz, a mining administrator in Saxony, his book Sylvicultura oeconomica, oder haußwirthliche Nachricht und Naturmäßige Anweisung zur wilden Baum-Zucht was the first comprehensive treatise about sustainable yield forestry. In the UK, and, to an extent, in continental Europe, the enclosure movement and the clearances favored enclosed private property; the Agrarian reformers, early economic writers and scientists tried to get rid of the traditional commons. At the time, an alleged tragedy of the commons together with fears of a Holznot, an imminent wood shortage played a watershed role in the controversies about cooperative land use patterns; the practice of establishing tree plantations in the British Isles was promoted by John Evelyn, though it had acquired some populari
Rocky Mountain elk
The Rocky Mountain elk is a subspecies of elk found in the Rocky Mountains and adjacent ranges of Western North America. The winter ranges are most common in open forests and floodplain marshes in the lower elevations. In the summer it migrates to alpine basins. Elk have a diverse habitat range that they can reside in but are most found in forest and forest edge habitat and in mountain regions they stay in higher elevations during warmer months and migrate down lower in the winter, they may come down the mountain and leave the forest into some grassland for part of the day but head back into the timber in the evening. The total wild population is about one million individuals; the Rocky Mountain elk was reintroduced in 1913 to Colorado from Wyoming after the near-extinction of the regional herds. While overhunting is a significant contributing factor, the elk’s near-extinction is attributed to human encroachment and destruction of their natural habitats and migratory corridors. A year twenty-one elk from Jackson Hole, Wyoming were reintroduced to South Dakota's Wind Cave National Park for population increase.
Conservation efforts brought the elk populations in New Mexico from near zero numbers in the late 1800s and early 1900s, to healthy populations in the 1930s in Northern New Mexico. Population numbers of elk in Nebraska continued to increase through the 1970s and 1980s, to a level in which complaints from landowners in the Pine Ridge region led to the implementation of liberal hunting seasons in the late 1980s. Elk numbers continued to increase through the 1990s to the present. All Rocky Mountain elk in Washington are the result of reintroductions conducted in the early 1900s from Yellowstone elk herds; these initial reintroductions have expanded their range and have been translocated within the State. Not all of these elk have all the habitat to be successful in large numbers. In 1990, feasibility studies were conducted to determine if wild, free-ranging elk still had a place in some of their former eastern haunts. Once this was complete, healthy source herds of Rocky Mountain elk from Arizona, New Mexico, North Dakota and Utah were used to introduce this elk subspecies to the former eastern elk range.
In recent years, elk from Utah have been used to reestablish a population in Kentucky. As of 2010, the Rocky Mountain elk herd has been diagnosed with a serious disorder called Chronic Wasting Disease. CWD affects the brain tissue of infected elk and is similar in symptoms to bovine spongiform encephalopathy known as mad-cow disease. There is no evidence to conclude that elk CWD is transmittable to humans, research concerning CWD and its effect on the eco-system continues. Environmental and CWD problems in Estes Park, Colorado and, on a greater scale, throughout the Western U. S. and North America have local and federal policy makers searching for solutions. The Rocky Mountain National Park and the Estes Park environments are physically disrupted by the migration of the elk, ranging in size from calves to full-grown 700-pound adults. Several indigenous butterfly and plant species are harmed the aspen groves that the elk herd of 3,000 animals decimates in its search for food; the elk population, while taxing the common food resources adversely affects native species that share the same food supply, such as the indigenous beavers.
Fish and Wildlife Habitat Management Leaflet. 1999. American Elk: Cervus elaphus. United States Department of Agriculture. Habitat Management Institute. Tule elk Manitoban elk Roosevelt elk Chronic Wasting Disease Alliance Rocky Mountain Elk Foundation
United States Forest Service
The United States Forest Service is an agency of the U. S. Department of Agriculture that administers the nation's 154 national forests and 20 national grasslands, which encompass 193 million acres. Major divisions of the agency include the National Forest System and Private Forestry, Business Operations, the Research and Development branch. Managing 25% of federal lands, it is the only major national land agency, outside the U. S. Department of the Interior; the concept of the National Forests was born from Theodore Roosevelt’s conservation group and Crockett Club, due to concerns regarding Yellowstone National Park beginning as early as 1875. In 1876, Congress formed the office of Special Agent in the Department of Agriculture to assess the quality and conditions of forests in the United States. Franklin B. Hough was appointed the head of the office. In 1881, the office was expanded into the newly formed Division of Forestry; the Forest Reserve Act of 1891 authorized withdrawing land from the public domain as "forest reserves," managed by the Department of the Interior.
In 1901, the Division of Forestry was renamed the Bureau of Forestry. The Transfer Act of 1905 transferred the management of forest reserves from the General Land Office of the Interior Department to the Bureau of Forestry, henceforth known as the United States Forest Service. Gifford Pinchot was the first United States Chief Forester in the Presidency of Theodore Roosevelt. Significant federal legislation affecting the Forest Service includes the Weeks Act of 1911, the Multiple Use – Sustained Yield Act of 1960, P. L. 86-517. L. 88-577. L. 94-588. L. 91-190. L. 95-313. L. 95-307. In February 2009, the Government Accountability Office evaluated whether the Forest Service should be moved from the Department of Agriculture to the Department of the Interior, which includes the National Park Service, the Fish and Wildlife Service, the Bureau of Land Management, managing some 438,000,000 acres of public land; as of 2009, the Forest Service has a total budget authority of $5.5 billion, of which 42% is spent fighting fires.
The Forest Service employs 34,250 employees in 750 locations, including 10,050 firefighters, 737 law enforcement personnel, 500 scientists. The mission of the Forest Service is "To sustain the health and productivity of the Nation's forests and grasslands to meet the needs of present and future generations." Its motto is "Caring for the land and serving people." As the lead federal agency in natural resource conservation, the US Forest Service provides leadership in the protection and use of the nation's forest and aquatic ecosystems. The agency's ecosystem approach to management integrates ecological and social factors to maintain and enhance the quality of the environment to meet current and future needs. Through implementation of land and resource management plans, the agency ensures sustainable ecosystems by restoring and maintaining species diversity and ecological productivity that helps provide recreation, timber, fish, wildlife and aesthetic values for current and future generations of people.
The everyday work of the Forest Service balances resource extraction, resource protection, providing recreation. The work includes managing 193,000,000 acres of national forest and grasslands, including 59,000,000 acres of roadless areas. Further, the Forest Service fought fires on 2,996,000 acres of land in 2007; the Forest Service organization includes ranger districts, national forests, research stations and research work units and the Northeastern Area Office for State and Private Forestry. Each level has responsibility for a variety of functions; the Chief of the Forest Service is a career federal employee. The Chief reports to the Under Secretary for Natural Resources and Environment in the U. S. Department of Agriculture, an appointee of the President confirmed by the Senate; the Chief's staff provides broad policy and direction for the agency, works with the Administration to develop a budget to submit to Congress, provides information to Congress on accomplishments, monitors activities of the agency.
There are five deputy chiefs for the following areas: National Forest System and Private Forestry and Development, Business Operations, Finance. The Forest Service Research and Development deputy area includes five research stations, the Forest Products Laboratory, the International Institute of Tropical Forestry, in Puerto Rico. Station directors, like regional foresters, report to the Chief. Research stations include Northern, Pacific Northwest, Pacific Southwest, Rocky Mountain, Southern. There are 92 research work units located at 67 sites throughout the United States. There are 80 Experimental Forests and Ranges that have been established progressively since 1908; the system provides places for long-term science and management studies in major vegetation types of the 195 million acres of public land administered by the Forest Service. Individual sites range from 47 to 22,500 ha in size. Operations of Experimental Forests and Ranges are directed by local research teams for the individual sites, by Research Stations for the regions in which they are located, at the level of the Forest Service.
Major themes in
The elevation of a geographic location is its height above or below a fixed reference point, most a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface. The term elevation is used when referring to points on the Earth's surface, while altitude or geopotential height is used for points above the surface, such as an aircraft in flight or a spacecraft in orbit, depth is used for points below the surface. Elevation is not to be confused with the distance from the center of the Earth. Due to the equatorial bulge, the summits of Mount Everest and Chimborazo have the largest elevation and the largest geocentric distance. GIS or geographic information system is a computer system that allows for visualizing, manipulating and storage of data with associated attributes. GIS offers better understanding of relationships of the landscape at different scales. Tools inside the GIS allow for manipulation of data for spatial cartography. A topographical map is the main type of map used to depict elevation through use of contour lines.
In a Geographic Information System, digital elevation models are used to represent the surface of a place, through a raster dataset of elevations. Digital terrain models are another way to represent terrain in GIS. USGS is developing a 3D Elevation Program to keep up with growing needs for high quality topographic data. 3DEP is a collection of enhanced elevation data in the form of high quality LiDAR data over the conterminous United States and the U. S. territories. There are three bare earth DEM layers in 3DEP which are nationally seamless at the resolution of 1/3, 1, 2 arcseconds; this map is derived from GTOPO30 data that describes the elevation of Earth's terrain at intervals of 30 arcseconds. It uses shading instead of contour lines to indicate elevation. Height Orthometric height Hypsography Geodesy Geodesy of North America Sea Level Datum of 1929 National Geodetic Vertical Datum of 1929 North American Vertical Datum of 1988 List of European cities by elevation List of highest mountains List of highest towns by country Normaal Amsterdams Peil Normalhöhennull Physical geography Table of the highest major summits of North America Temperature lapse rate Topographic isolation Topographic prominence Topography Vertical pressure variation U.
S. National Geodetic Survey website Geodetic Glossary @ NGS NGVD 29 to NAVD 88 online elevation converter @ NGS United States Geological Survey website Geographical Survey Institute Downloadable ETOPO2 Raw Data Database Downloadable ETOPO5 Raw Data Database Find the elevation of any place
Salmon River (Idaho)
The Salmon River is located in Idaho in the northwestern United States. The Salmon is known as "The River of No Return", it flows for 425 miles through central Idaho, draining a rugged, thinly populated watershed of 14,000 square miles and dropping more than 7,000 feet between its headwaters, near Galena Summit above the Sawtooth Valley in the Sawtooth National Recreation Area, its confluence with the Snake River. Measured at White Bird, its average discharge is 11,060 cubic feet per second, it is one of the largest rivers in the continental United States without a single dam on its mainstem. Cities located along the Salmon River include Stanley, Challis, Salmon and White Bird. Redfish Lake and Little Redfish Lake near Stanley, which flow into the river via Redfish Lake Creek, are the terminus of the longest Pacific sockeye salmon migration in North America; the lower half of the river provides the time zone boundary for the state, with northern Idaho on Pacific time and the rest of the state on Mountain time.
The Salmon River flows through the mountains of central and eastern Idaho. The main stem rises in the Sawtooth Range at over 9,200 feet in elevation, several miles northwest of Norton Peak. For the first 30 miles, it flows north through the Sawtooth Valley turns east at Stanley, receiving the Yankee Fork shortly below that point and the East Fork further downstream; the river flows northeast, receiving the Pahsimeroi River at Ellis and the Lemhi River at Salmon, Idaho east of the Lemhi Range. North of Salmon, the river is joined by the North Fork, before turning west into over 200 miles of continuous canyons through the Salmon River and Clearwater Mountains – some of the most rugged and isolated terrain in the contiguous United States. Exhibiting upwards of 7,000 feet of vertical relief, the Salmon River canyons are some of the deepest in the U. S. surpassing the Grand Canyon and second only to the Snake River's Hells Canyon on the Idaho–Oregon border. Here, the river is joined by the Middle Fork and South Fork.
Ten miles downstream of its confluence with the Middle Fork, the Salmon River becomes the dividing line for the two time zones in Idaho: Mountain time to the south, Pacific time to the north, bisecting the state at 45½ degrees north latitude. The river turns abruptly north at the confluence with the Little Salmon River at Riggins, about 87 miles above its mouth. From there the river flows due north, with U. S. Route 95 on its east bank until a few miles before White Bird; the Salmon River is the longest river system contained within a single U. S. state. The Salmon River area has been home to people for at least the last 8,000 years. Much of the area was inhabited including the Nez Perce; the river was considered sacred ground and a rich source of food for the indigenous people of the area, who relied on the abundant salmon species and other wildlife. In August 1805, just after crossing the Continental Divide of the Americas and Clark ventured down the Salmon River, but found it to be too rough to be navigable.
Clark wrote:... I shall in justice to Capt. Lewis, the first white man on this fork of the Columbia Call this Louis's river.... The Westerly fork of the Columbia River is double the size of the Easterley fork & below those forks the river is... 100 yards wide, it is rapid & Sholey water Clear but little timber. The honor didn't last long. Clark had thought that the Salmon River was the Snake River, thus he called it the "Westerly fork of the Columbia"; the Snake River retained the variant name. In the 1860s, placer deposits of gold were found along the river, a gold rush began. Miners came to the area. Many historic and present day mines can be seen while traveling along the river. Several national forests and Sawtooth National Recreation Area provide for numerous recreation opportunities within the river's watershed. Two segments are protected as Scenic Rivers; the Middle Fork was one of the original eight rivers designated Wild and Scenic in 1968, is considered the "crown jewel" of the Wild and Scenic system.
The Salmon is a popular destination for whitewater kayaking and rafting. The canyons of the Salmon allow for magnificent views of the complex geology of the region; the Frank Church-River of No Return Wilderness Area includes one of the deepest canyons in the continental United States, which at 7,000 feet of vertical relief, is deeper than the Grand Canyon. Both the Middle Fork and Main Fork travel through the Frank Church-River of No Return Wilderness Area; the Middle Fork is about 110 miles long. The Middle Fork raft trip run ends 7 miles prior to the beginning of the Main Fork run; the South Fork of the Salmon flows through Payette National Forest and enters the Wild and Scenic Main Fork at Mackay Bar. The Main Fork raft trip ends ab
Gold is a chemical element with symbol Au and atomic number 79, making it one of the higher atomic number elements that occur naturally. In its purest form, it is a bright reddish yellow, soft and ductile metal. Chemically, gold is a group 11 element, it is solid under standard conditions. Gold occurs in free elemental form, as nuggets or grains, in rocks, in veins, in alluvial deposits, it occurs in a solid solution series with the native element silver and naturally alloyed with copper and palladium. Less it occurs in minerals as gold compounds with tellurium. Gold is resistant to most acids, though it does dissolve in aqua regia, a mixture of nitric acid and hydrochloric acid, which forms a soluble tetrachloroaurate anion. Gold is insoluble in nitric acid, which dissolves silver and base metals, a property that has long been used to refine gold and to confirm the presence of gold in metallic objects, giving rise to the term acid test. Gold dissolves in alkaline solutions of cyanide, which are used in mining and electroplating.
Gold dissolves in mercury, forming amalgam alloys. A rare element, gold is a precious metal, used for coinage and other arts throughout recorded history. In the past, a gold standard was implemented as a monetary policy, but gold coins ceased to be minted as a circulating currency in the 1930s, the world gold standard was abandoned for a fiat currency system after 1971. A total of 186,700 tonnes of gold exists above ground, as of 2015; the world consumption of new gold produced is about 50% in jewelry, 40% in investments, 10% in industry. Gold's high malleability, resistance to corrosion and most other chemical reactions, conductivity of electricity have led to its continued use in corrosion resistant electrical connectors in all types of computerized devices. Gold is used in infrared shielding, colored-glass production, gold leafing, tooth restoration. Certain gold salts are still used as anti-inflammatories in medicine; as of 2017, the world's largest gold producer by far was China with 440 tonnes per year.
Gold is the most malleable of all metals. It can be drawn into a monoatomic wire, stretched about twice before it breaks; such nanowires distort via formation and migration of dislocations and crystal twins without noticeable hardening. A single gram of gold can be beaten into a sheet of 1 square meter, an avoirdupois ounce into 300 square feet. Gold leaf can be beaten thin enough to become semi-transparent; the transmitted light appears greenish blue, because gold reflects yellow and red. Such semi-transparent sheets strongly reflect infrared light, making them useful as infrared shields in visors of heat-resistant suits, in sun-visors for spacesuits. Gold is a good conductor of electricity. Gold has a density of 19.3 g/cm3 identical to that of tungsten at 19.25 g/cm3. By comparison, the density of lead is 11.34 g/cm3, that of the densest element, osmium, is 22.588±0.015 g/cm3. Whereas most metals are gray or silvery white, gold is reddish-yellow; this color is determined by the frequency of plasma oscillations among the metal's valence electrons, in the ultraviolet range for most metals but in the visible range for gold due to relativistic effects affecting the orbitals around gold atoms.
Similar effects impart a golden hue to metallic caesium. Common colored gold alloys include the distinctive eighteen-karat rose gold created by the addition of copper. Alloys containing palladium or nickel are important in commercial jewelry as these produce white gold alloys. Fourteen-karat gold-copper alloy is nearly identical in color to certain bronze alloys, both may be used to produce police and other badges. White gold alloys can be made with nickel. Fourteen- and eighteen-karat gold alloys with silver alone appear greenish-yellow and are referred to as green gold. Blue gold can be made by alloying with iron, purple gold can be made by alloying with aluminium. Less addition of manganese, aluminium and other elements can produce more unusual colors of gold for various applications. Colloidal gold, used by electron-microscopists, is red. Gold has only one stable isotope, 197Au, its only occurring isotope, so gold is both a mononuclidic and monoisotopic element. Thirty-six radioisotopes have been synthesized, ranging in atomic mass from 169 to 205.
The most stable of these is 195Au with a half-life of 186.1 days. The least stable is 171Au. Most of gold's radioisotopes with atomic masses below 197 decay by some combination of proton emission, α decay, β+ decay; the exceptions are 195Au, which decays by electron capture, 196Au, which decays most by electron capture with a minor β− decay path. All of gold's radioisotopes with atomic masses above 197 decay by β− decay. At least 32 nuclear isomers have been characterized, ranging in atomic mass from 170 to 200. Within that range, only 178Au, 180Au, 181Au, 182Au, 188Au do not have isomers. Gold's most stable isomer is 198m2Au with a half-life of 2.27 days. Gold's least stable isomer is 177m2Au with a half-life of only 7 ns. 184m1Au has three decay paths: β+ decay, isomeric