Iron is a chemical element with symbol Fe and atomic number 26. It is a metal, that belongs to group 8 of the periodic table, it is by mass the most common element on Earth, forming much of Earth's inner core. It is the fourth most common element in the Earth's crust. Pure iron is rare on the Earth's crust being limited to meteorites. Iron ores are quite abundant, but extracting usable metal from them requires kilns or furnaces capable of reaching 1500 °C or higher, about 500 °C higher than what is enough to smelt copper. Humans started to dominate that process in Eurasia only about 2000 BCE, iron began to displace copper alloys for tools and weapons, in some regions, only around 1200 BCE; that event is considered the transition from the Bronze Age to the Iron Age. Iron alloys, such as steel and special steels are now by far the most common industrial metals, because of their mechanical properties and their low cost. Pristine and smooth pure iron surfaces are mirror-like silvery-gray. However, iron reacts with oxygen and water to give brown to black hydrated iron oxides known as rust.
Unlike the oxides of some other metals, that form passivating layers, rust occupies more volume than the metal and thus flakes off, exposing fresh surfaces for corrosion. The body of an adult human contains about 3 to 5 grams of elemental iron in hemoglobin and myoglobin; these two proteins play essential roles in vertebrate metabolism oxygen transport by blood and oxygen storage in muscles. To maintain the necessary levels, human iron metabolism requires a minimum of iron in the diet. Iron is the metal at the active site of many important redox enzymes dealing with cellular respiration and oxidation and reduction in plants and animals. Chemically, the most common oxidation states of iron are +2 and +3. Iron shares many properties of other transition metals, including the other group 8 elements and osmium. Iron forms compounds in a wide range of oxidation states, −2 to +7. Iron forms many coordination compounds. At least four allotropes of iron are known, conventionally denoted α, γ, δ, ε; the first three forms are observed at ordinary pressures.
As molten iron cools past its freezing point of 1538 °C, it crystallizes into its δ allotrope, which has a body-centered cubic crystal structure. As it cools further to 1394 °C, it changes to its γ-iron allotrope, a face-centered cubic crystal structure, or austenite. At 912 °C and below, the crystal structure again becomes the bcc α-iron allotrope; the physical properties of iron at high pressures and temperatures have been studied extensively, because of their relevance to theories about the cores of the Earth and other planets. Above 10 GPa and temperatures of a few hundred kelvin or less, α-iron changes into another hexagonal close-packed structure, known as ε-iron; the higher-temperature γ-phase changes into ε-iron, but does so at higher pressure. Some controversial experimental evidence exists for a stable β phase at pressures above 50 GPa and temperatures of at least 1500 K, it is supposed to have a double hcp structure. The inner core of the Earth is presumed to consist of an iron-nickel alloy with ε structure.
The melting and boiling points of iron, along with its enthalpy of atomization, are lower than those of the earlier 3d elements from scandium to chromium, showing the lessened contribution of the 3d electrons to metallic bonding as they are attracted more and more into the inert core by the nucleus. This same trend appears for ruthenium but not osmium; the melting point of iron is experimentally well defined for pressures less than 50 GPa. For greater pressures, published data still varies by tens of gigapascals and over a thousand kelvin. Below its Curie point of 770 °C, α-iron changes from paramagnetic to ferromagnetic: the spins of the two unpaired electrons in each atom align with the spins of its neighbors, creating an overall magnetic field; this happens because the orbitals of those two electrons do not point toward neighboring atoms in the lattice, therefore are not involved in metallic bonding. In the absence of an external source of magnetic field, the atoms get spontaneously partitioned into magnetic domains, about 10 micrometres across, such that the atoms in each domain have parallel spins, but different domains have other orientations.
Thus a macroscopic piece of iron will have a nearly zero overall magnetic field. Application of an external magnetic field causes the domains that are magnetized in the same general direction to grow at the expense of adjacent ones that point in other directions, reinforcing the external field; this effect is exploited in devices that needs to channel magnetic fields, such as electrical transformers, magnetic recording heads, electric motors. Impurities, lattice defects, or grain and particle boundaries can "pin" the domains in the new positions, so that the effect persists after the external field is removed -- thus turning the iron object into a magnet. Similar behavior is exhibited by some iron compounds, such as the fer
The potato is a starchy, tuberous crop from the perennial nightshade Solanum tuberosum. In many contexts, potato refers to the edible tuber, but it can refer to the plant itself. Common or slang terms include tater and spud. Potatoes were introduced to Europe in the second half of the 16th century by the Spanish. Today they are a staple food in many parts of the world and an integral part of much of the world's food supply; as of 2014, potatoes were the world's fourth-largest food crop after maize and rice. Wild potato species can be found from the United States to southern Chile; the potato was believed to have been domesticated independently in multiple locations, but genetic testing of the wide variety of cultivars and wild species traced a single origin for potatoes. In the area of present-day southern Peru and extreme northwestern Bolivia, from a species in the Solanum brevicaule complex, potatoes were domesticated 7,000–10,000 years ago. In the Andes region of South America, where the species is indigenous, some close relatives of the potato are cultivated.
Following millennia of selective breeding, there are now over 1,000 different types of potatoes. Over 99% of presently cultivated potatoes worldwide descended from varieties that originated in the lowlands of south-central Chile, which have displaced popular varieties from the Andes; the importance of the potato as a food source and culinary ingredient varies by region and is still changing. It remains an essential crop in Europe eastern and central Europe, where per capita production is still the highest in the world, while the most rapid expansion in production over the past few decades has occurred in southern and eastern Asia, with China and India leading the world in overall production as of 2014. Being a nightshade similar to tomatoes, the vegetative and fruiting parts of the potato contain the toxin solanine and are not fit for human consumption. Normal potato tubers that have been grown and stored properly produce glycoalkaloids in amounts small enough to be negligible to human health, but if green sections of the plant are exposed to light, the tuber can accumulate a high enough concentration of glycoalkaloids to affect human health.
The English word potato comes from Spanish patata. The Spanish Royal Academy says the Spanish word is a hybrid of the Taíno batata and the Quechua papa; the name referred to the sweet potato although the two plants are not related. The 16th-century English herbalist John Gerard referred to sweet potatoes as "common potatoes", used the terms "bastard potatoes" and "Virginia potatoes" for the species we now call "potato". In many of the chronicles detailing agriculture and plants, no distinction is made between the two. Potatoes are referred to as "Irish potatoes" or "white potatoes" in the United States, to distinguish them from sweet potatoes; the name spud for a small potato comes from the digging of soil prior to the planting of potatoes. The word has an unknown origin and was used as a term for a short knife or dagger related to the Latin "spad-" a word root meaning "sword", it subsequently transferred over to a variety of digging tools. Around 1845, the name transferred to the tuber itself, the first record of this usage being in New Zealand English.
The origin of the word "spud" has erroneously been attributed to an 18th-century activist group dedicated to keeping the potato out of Britain, calling itself The Society for the Prevention of Unwholesome Diet. It was Mario Pei's 1949 The Story of Language. Pei writes, "the potato, for its part, was in disrepute some centuries ago; some Englishmen who did not fancy potatoes formed a Society for the Prevention of Unwholesome Diet. The initials of the main words in this title gave rise to spud." Like most other pre-20th century acronymic origins, this is false, there is no evidence that a Society for the Prevention of Unwholesome Diet existed. Potato plants are herbaceous perennials that grow about 60 cm high, depending on variety, with the leaves dying back after flowering and tuber formation, they bear white, red, blue, or purple flowers with yellow stamens. In general, the tubers of varieties with white flowers have white skins, while those of varieties with colored flowers tend to have pinkish skins.
Potatoes are cross-pollinated by insects such as bumblebees, which carry pollen from other potato plants, though a substantial amount of self-fertilizing occurs as well. Tubers form in response to decreasing day length, although this tendency has been minimized in commercial varieties. After flowering, potato plants produce small green fruits that resemble green cherry tomatoes, each containing about 300 seeds. Like all parts of the plant except the tubers, the fruit contain the toxic alkaloid solanine and are therefore unsuitable for consumption. All new potato varieties are grown from seeds called "true potato seed", "TPS" or "botanical seed" to distinguish it from seed tubers. New varieties grown from seed can be propagated vegetatively by planting tubers, pieces of tubers cut to include at least one or two eyes, or cuttings, a practice used in greenhouses for the production of healthy seed tubers. Plants propagated from tubers are clones of the parent, whereas those propagated from seed produce a range of different varieties.
There are about 5,000 potato varieties worldwide. Three thousand of them are found in the Andes alone in Peru, Ecuador and Colombia, they belong to eight or nine species, dependin
Color, or colour, is the characteristic of human visual perception described through color categories, with names such as red, yellow, blue, or purple. This perception of color derives from the stimulation of cone cells in the human eye by electromagnetic radiation in the visible spectrum. Color categories and physical specifications of color are associated with objects through the wavelength of the light, reflected from them; this reflection is governed by the object's physical properties such as light absorption, emission spectra, etc. By defining a color space, colors can be identified numerically by coordinates, which in 1931 were named in global agreement with internationally agreed color names like mentioned above by the International Commission on Illumination; the RGB color space for instance is a color space corresponding to human trichromacy and to the three cone cell types that respond to three bands of light: long wavelengths, peaking near 564–580 nm. There may be more than three color dimensions in other color spaces, such as in the CMYK color model, wherein one of the dimensions relates to a color's colorfulness).
The photo-receptivity of the "eyes" of other species varies from that of humans and so results in correspondingly different color perceptions that cannot be compared to one another. Honeybees and bumblebees for instance have trichromatic color vision sensitive to ultraviolet but is insensitive to red. Papilio butterflies may have pentachromatic vision; the most complex color vision system in the animal kingdom has been found in stomatopods with up to 12 spectral receptor types thought to work as multiple dichromatic units. The science of color is sometimes called chromatics, colorimetry, or color science, it includes the study of the perception of color by the human eye and brain, the origin of color in materials, color theory in art, the physics of electromagnetic radiation in the visible range. Electromagnetic radiation is characterized by its intensity; when the wavelength is within the visible spectrum, it is known as "visible light". Most light sources emit light at many different wavelengths.
Although the spectrum of light arriving at the eye from a given direction determines the color sensation in that direction, there are many more possible spectral combinations than color sensations. In fact, one may formally define a color as a class of spectra that give rise to the same color sensation, although such classes would vary among different species, to a lesser extent among individuals within the same species. In each such class the members are called metamers of the color in question; the familiar colors of the rainbow in the spectrum—named using the Latin word for appearance or apparition by Isaac Newton in 1671—include all those colors that can be produced by visible light of a single wavelength only, the pure spectral or monochromatic colors. The table at right shows approximate wavelengths for various pure spectral colors; the wavelengths listed are as measured in vacuum. The color table should not be interpreted as a definitive list—the pure spectral colors form a continuous spectrum, how it is divided into distinct colors linguistically is a matter of culture and historical contingency.
A common list identifies six main bands: red, yellow, green and violet. Newton's conception included a seventh color, between blue and violet, it is possible that what Newton referred to as blue is nearer to what today is known as cyan, that indigo was the dark blue of the indigo dye, being imported at the time. The intensity of a spectral color, relative to the context in which it is viewed, may alter its perception considerably; the color of an object depends on both the physics of the object in its environment and the characteristics of the perceiving eye and brain. Physically, objects can be said to have the color of the light leaving their surfaces, which depends on the spectrum of the incident illumination and the reflectance properties of the surface, as well as on the angles of illumination and viewing; some objects not only reflect light, but transmit light or emit light themselves, which contributes to the color. A viewer's perception of the object's color depends not only on the spectrum of the light leaving its surface, but on a host of contextual cues, so that color differences between objects can be discerned independent of the lighting spectrum, viewing angle, etc.
This effect is known as color constancy. Some generalizations of the physics can be drawn, neglecting perceptual effects for now: Light arriving at an opaque surface is either reflected "specularly", scattered, or absorbed – or some combination of these. Opaque objects that do not reflect specularly have their color determined by which wavelengths of light they scatter strongly. If objects scatter all wavelengths with r
William Henry Jackson
William Henry Jackson was an American painter, Civil War veteran, geological survey photographer and an explorer famous for his images of the American West. He was a great-great nephew of the progenitor of America's national symbol Uncle Sam. Jackson was born in Keeseville, New York, on April 4, 1843, the first of seven children born to George Hallock Jackson and Harriet Maria Allen. Harriet, a talented water-colorist, was a graduate of the Troy Female Academy the Emma Willard School. Painting was his passion from a young age. By age 19, he had become a talented artist of American pre-Civil War visual arts. Orson Squire Fowler wrote that Jackson was "excellent as a painter". After his childhood in Troy, New York, Rutland, Jackson enlisted in October 1862 as a 19-year-old private in Company K of the 12th Vermont Infantry of the Union Army Jackson spent much of his free time sketching drawings of his friends and various scenes of Army camp life that he sent home to his family as his way of letting them know he was safe.
He served in the American Civil War for nine months including one major battle, the Battle of Gettysburg. Jackson spent most of his tour on garrison duty and helped guard a supply train during the engagement, his regiment mustered out on July 14, 1863. Jackson returned to Rutland, where he worked as an artistic painter in post-Civil War American society. Having broken his engagement to Miss Carolina Eastman, he left Vermont for the American West. In 1866 Jackson boarded a Union Pacific Railroad train and traveled until it reached the end of the line at that time, about one hundred miles west of Omaha, where he joined a wagon train heading west to Great Salt Lake as a bullwhacker, on the Oregon Trail. In 1867 along with his brother Edward Jackson he settled down in Omaha and entered the photography business. On ventures that lasted for several days, Jackson acted as a "missionary to the Indians" around the Omaha region, it was there that Jackson made his now famous photographs of the American Indians: Osages, Pawnees and Omahas.
In 1869 Jackson won a commission from the Union Pacific to document the scenery along the various railroad routes for promotional purposes. When his work was discovered by Ferdinand Hayden, organizing a geologic survey to explore the Yellowstone River region, he was asked to join the expedition; the following year, he got a last-minute invitation to join the 1870 U. S. government survey of the Yellowstone River and Rocky Mountains led by Ferdinand Hayden. He was a member of the Hayden Geological Survey of 1871 which led to the creation of Yellowstone National Park. Painter Thomas Moran was part of the expedition, the two artists worked together to document the Yellowstone region. Hayden's surveys were annual multidisciplinary expeditions meant to chart the unexplored west, observe flora and geological conditions, identify navigational routes, so as official photographer for the survey, Jackson was in a position to capture the first photographs of legendary landmarks of the West; these photographs played an important role in convincing Congress in 1872 to establish Yellowstone National Park, the first national park of the U.
S. His involvement with Hayden's survey established his reputation as one of the most accomplished explorers of the American continent. Among Hayden's party were Jackson, geologist George Allen, mineralogist Albert Peale, topographical artist Henry Elliot and other scientists who collected numerous wildlife specimens and other natural data. Jackson worked in multiple camera and plate sizes, under conditions that were incredibly difficult, his photography was based on the collodion process invented in 1848 and published in 1851 by Frederick Scott Archer. Jackson traveled with as many as three camera-types—a stereographic camera, a "whole-plate" or 8x10" plate-size camera, one larger, as large as 18x22"; these cameras required fragile, heavy glass plates, which had to be coated and developed onsite, before the wet-collodion emulsion dried. Without light metering equipment or sure emulsion speeds, exposure times required inspired guesswork, between five seconds and twenty minutes depending on light conditions.
Preparing, developing, washing drying a single image could take the better part of an hour. Washing the plates in 160 °F hot spring water cut the drying time by more than half, while using water from snow melted and warmed in his hands slowed down the processing substantially, his photographic division of 5 to 7 men carried photographic equipment on the backs of mules and rifles on their shoulders. Jackson's life experience was welcomed; the weight of the glass plates and the portable darkroom limited the number of possible exposures on any one trip, these images were taken in primitive and physically challenging conditions. Once when the mule lost its footing, Jackson lost a month's work, having to return to untracked Rocky Mountain landscapes to remake the pictures, one of, his celebrated view of the Mount of the Holy Cross. Despite the delays and setbacks Jackson returned with conclusive photographic evidence of the various western landmarks that had seemed only a fantastic myth: the Grand Tetons, Old Faithful and the rest of the Yellowstone region, Colorado's Rockies and the Mount of the Holy Cross, the uncooperative Ute Indians.
Jackson's photographs of Yellowstone helped convince the U
A flash flood is a rapid flooding of low-lying areas: washes, dry lakes and basins. It may be caused by heavy rain associated with a severe thunderstorm, tropical storm, or meltwater from ice or snow flowing over ice sheets or snowfields. Flash floods may occur after the collapse of a natural ice or debris dam, or a human structure such as a man-made dam, as occurred before the Johnstown Flood of 1889. Flash floods are distinguished from regular floods by having a timescale of fewer than six hours between rainfall and the onset of flooding; the water, temporarily available is used by plants with rapid germination and short growth cycles and by specially adapted animal life. Flash floods can occur under several types of conditions. Flash flooding occurs when it rains on saturated soil or dry soil that has poor absorption ability; the runoff collects in gullies and streams and, as they join to form larger volumes forms a fast flowing front of water and debris. Flash floods most occur in dry areas that have received precipitation, but they may be seen anywhere downstream from the source of the precipitation many miles from the source.
In areas on or near volcanoes, flash floods have occurred after eruptions, when glaciers have been melted by the intense heat. Flash floods are known to occur in the highest mountain ranges of the United States and are common in the arid plains of the Southwestern United States. Flash flooding can be caused by extensive rainfall released by hurricanes and other tropical storms, as well as the sudden thawing effect of ice dams. Human activities can cause flash floods to occur; when dams fail, a large quantity of water can destroy everything in its path. The United States National Weather Service gives the advice "Turn Around, Don't Drown" for flash floods. Many people tend to underestimate the dangers of flash floods. What makes flash floods most dangerous is their sudden nature and fast-moving water. A vehicle provides little to no protection against being swept away. More than half of the fatalities attributed to flash floods are people swept away in vehicles when trying to cross flooded intersections.
As little as 2 feet of water is enough to carry away most SUV-sized vehicles. The U. S. National Weather Service reported in 2005 that, using a national 30-year average, more people die yearly in floods, 127 on average, than by lightning, tornadoes, or hurricanes. In deserts, flash floods can be deadly for several reasons. First, storms in arid regions are infrequent, but they can deliver an enormous amount of water in a short time. Second, these rains fall on poorly absorbent and clay-like soil, which increases the amount of runoff that rivers and other water channels have to handle; these regions tend not to have the infrastructure that wetter regions have to divert water from structures and roads, such as storm drains and retention basins, either because of sparse population or poverty, or because residents believe the risk of flash floods is not high enough to justify the expense. In fact, in some areas, desert roads cross a dry river and creek beds without bridges. From the driver's perspective, there may be clear weather, when a river unexpectedly forms ahead of or around the vehicle in a matter of seconds.
The lack of regular rain to clear water channels may cause flash floods in deserts to be headed by large amounts of debris, such as rocks and logs. Deep slot canyons can be dangerous to hikers as they may be flooded by a storm that occurs on a mesa miles away; the flood sweeps through the canyon. 1889: Johnstown Flood, Pennsylvania, U. S.: more than 2,200 people dead 1903: Heppner Flood of 1903. S.: 115 dead 1938: Kopuawhara flash flood of 1938, Mahia Peninsula, New Zealand: 21 dead 1952: Lynmouth disaster, England: 34 dead 1963: Petra Flash Flood, Jordan: 23 dead 1963: Vajont dam disaster, Italy: 1910 dead 1967: Flash flood in Lisbon, Portugal: 464 dead 1969: Nelson County, Virginia, US: 123 dead 1971: Kuala Lumpur floods, Malaysia: 32 dead 1972: The Black Hills flood, South Dakota, U. S.: 238 dead 1976: The Big Thompson River flood, Colorado, U. S.: 143 dead 1997: Antelope Canyon, a popular tourist attraction north of Page, Arizona:11 dead 2003: Bukit Lawang in Indonesia 239 people were killed 2006: Jember Regency in Indonesia 59 people dead 2007: Sudan floods, 64 dead.
2009: September 26 in Metro Manila Marikina city, Taguig City, Pasig City. It submerged several municipalities under feet of deep water for several weeks. 2009: October 1, Messina, 37 dead. See 2009 Messina floods and mudslides. 2010: Madeira archipelago, 42 dead 2011: Lockyer Valley, Australia. 21 dead in the town of Grantham. 2011: Philippines, Cagayan de Oro and Iligan City, 17 December 2011. At least 1200 dead 2012: May 5, Nearly three weeks of damming left 72 dead in the Seti Gorge in Upper Seti Basin. Rock and avalanche fall from the western part of Annapurna IV mountain in Nepal. 2012: Krasnodarskiy Kray, Russia. 172 dead following a flash flood that struck at 2 A. M. local time on 7 July. Main cities that were hit are Gelendzhik. 2013: Uttarakhand, India: 822 dead 2013: Novemb
The Yellowstone River is a tributary of the Missouri River 692 miles long, in the western United States. Considered the principal tributary of the upper Missouri, the river and its tributaries drain a wide area stretching from the Rocky Mountains in the vicinity of the Yellowstone National Park across the mountains and high plains of southern Montana and northern Wyoming; the Yellowstone River Watershed is a river basin spanning 37,167 square miles across Montana, with minor extensions into Wyoming and North Dakota toward headwaters and terminus, respectively. The Yellowstone Basin Watershed contains a system of rivers, including the Yellowstone River, four tributary basins: the Clarks Fork Yellowstone, Wind River and Bighorn River, Tongue River, Powder River; these rivers form tributaries to the Missouri River. The mainstem of the Yellowstone River is more than 700 miles long. At the headwaters, elevations exceed 12,800 feet above sea level and descends to 1,850 feet at the confluence with the Missouri River in North Dakota.
The watershed spans 34,167 square miles. The area contains many lakes, including Yellowstone Lake. There are no storage dams located on the mainstem of the Yellowstone River. However, the watershed contains five major reservoirs: Bull Lake, Buffalo, Tongue River, Lake De Smet reservoirs; the river rises in northwestern Wyoming in the Absaroka Range, on the Continental Divide in southwestern Park County. The river starts where the South Fork of the Yellowstone River converge; the North Fork, the larger of the two forks, flows from Younts Peak. The South Fork flows from the southern slopes of Thorofare Mountain; the Yellowstone River flows northward through Yellowstone National Park and draining Yellowstone Lake dropping over the Upper and Lower Yellowstone Falls at the head of the Grand Canyon of the Yellowstone within the confines of the park. After passing through the Black Canyon of the Yellowstone downstream of the Grand Canyon, the river flows northward into Montana between the northern Absaroka Range and the Gallatin Range in Paradise Valley.
The river emerges from the mountains near the town of Livingston, where it turns eastward and northeastward, flowing across the northern Great Plains past the city of Billings. East of Billings, it is joined by the Bighorn River. Further downriver, it is joined by the Tongue near Miles City, by the Powder in eastern Montana, it flows into North Dakota just upstream from Lake Sakakawea. In Montana the river has been used extensively for irrigation since the 1860s. In its upper reaches, within Yellowstone Park and the mountains of Montana, it is a popular destination for fly fishing; the Yellowstone is a Class I river from the Yellowstone National Park boundary to the North Dakota border for the purposes of stream access for recreational purposes. The division of water rights to the entire Yellowstone River Basin among Wyoming and North Dakota, governed by a 1950 compact, was disputed in a 2010 lawsuit brought directly in the U. S. Supreme Court by Montana against Wyoming. Oral argument took place in January 2011.
On May 2, 2011, the Court held 7-2 that Montana had no valid claim for diminution of its water, since Wyoming was irrigating the same acreage as always, albeit by a more modern method that returned less runoff to go downstream to Montana. The name is believed to have been derived from the Minnetaree Indian name Mi tse a-da-zi. Common lore states that the name came from the yellow-colored rocks along the Grand Canyon of the Yellowstone, but the Minnetaree never lived along the upper stretches of the Yellowstone; some scholars think that the river was named after yellow-colored sandstone bluffs on the lower Yellowstone, instead. The Crow Indians, who lived along the upper Yellowstone in Southern Montana, called it E-chee-dick-karsh-ah-shay. Translating the Minnetaree name, French trappers called the river Roche Jaune, a name used by mountain men until the mid-19th century. Independently and Clark recorded the English translation of Yellow Stone for the river, after encountering the Minnetaree in 1805.
With expanding settlement by people from the United States, the English name became the most used. The river was explored in 1806 by William Clark during the return voyage of the Lewis and Clark Expedition. Clark's Fork of the river was named for him. Most of the natural features of the Yellowstone Valley that were not named by Lewis and Clark were named by pioneer steamboat captain Grant Marsh. Marsh was selected by the Army for an exploratory expedition in 1873 on his boat the Key West. Marsh kept a detailed log, the names he bestowed were recorded by a representative of the War Department and applied on official maps; these include:- Forsyth Butte, named in honor of Brevet Brig. Gen. George Alexander Forsyth, commander of the expedition. - Cut Nose Butte, Chimney Rock and Diamond Island, for their resemblance to these objects. - Seven Sisters Islands, in remembrance of Captain Marsh's seven sisters. - Crittenden Island, for General T. L. Crittenden, who commanded the 17th Infantry, garrisoned at posts along the Missouri River.
- Mary Island, for the chambermaid on the Key West, wife of the steward, "Dutch Jake." - Reno Island, for Major Marcus A. Reno, of the 7th Cavalry. - Schindel Island, for Major M. Bryant, commanding t
A glacier is a persistent body of dense ice, moving under its own weight. Glaciers deform and flow due to stresses induced by their weight, creating crevasses and other distinguishing features, they abrade rock and debris from their substrate to create landforms such as cirques and moraines. Glaciers form only on land and are distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water. On Earth, 99% of glacial ice is contained within vast ice sheets in the polar regions, but glaciers may be found in mountain ranges on every continent including Oceania's high-latitude oceanic island countries such as New Zealand and Papua New Guinea. Between 35°N and 35°S, glaciers occur only in the Himalayas, Rocky Mountains, a few high mountains in East Africa, New Guinea and on Zard Kuh in Iran. Glaciers cover about 10 percent of Earth's land surface. Continental glaciers cover nearly 13 million km2 or about 98 percent of Antarctica's 13.2 million km2, with an average thickness of 2,100 m.
Greenland and Patagonia have huge expanses of continental glaciers. Glacial ice is the largest reservoir of fresh water on Earth. Many glaciers from temperate and seasonal polar climates store water as ice during the colder seasons and release it in the form of meltwater as warmer summer temperatures cause the glacier to melt, creating a water source, important for plants and human uses when other sources may be scant. Within high-altitude and Antarctic environments, the seasonal temperature difference is not sufficient to release meltwater. Since glacial mass is affected by long-term climatic changes, e.g. precipitation, mean temperature, cloud cover, glacial mass changes are considered among the most sensitive indicators of climate change and are a major source of variations in sea level. A large piece of compressed ice, or a glacier, appears blue, as large quantities of water appear blue; this is. The other reason for the blue color of glaciers is the lack of air bubbles. Air bubbles, which give a white color to ice, are squeezed out by pressure increasing the density of the created ice.
The word glacier is a loanword from French and goes back, via Franco-Provençal, to the Vulgar Latin glaciārium, derived from the Late Latin glacia, Latin glaciēs, meaning "ice". The processes and features caused by or related to glaciers are referred to as glacial; the process of glacier establishment and flow is called glaciation. The corresponding area of study is called glaciology. Glaciers are important components of the global cryosphere. Glaciers are categorized by their morphology, thermal characteristics, behavior. Cirque glaciers form on the slopes of mountains. A glacier that fills a valley is called a valley glacier, or alternatively an alpine glacier or mountain glacier. A large body of glacial ice astride a mountain, mountain range, or volcano is termed an ice cap or ice field. Ice caps have an area less than 50,000 km2 by definition. Glacial bodies larger than 50,000 km2 are called continental glaciers. Several kilometers deep, they obscure the underlying topography. Only nunataks protrude from their surfaces.
The only extant ice sheets are the two that cover most of Greenland. They contain vast quantities of fresh water, enough that if both melted, global sea levels would rise by over 70 m. Portions of an ice sheet or cap that extend into water are called ice shelves. Narrow, fast-moving sections of an ice sheet are called ice streams. In Antarctica, many ice streams drain into large ice shelves; some drain directly into the sea with an ice tongue, like Mertz Glacier. Tidewater glaciers are glaciers that terminate in the sea, including most glaciers flowing from Greenland, Antarctica and Ellesmere Islands in Canada, Southeast Alaska, the Northern and Southern Patagonian Ice Fields; as the ice reaches the sea, pieces break off, or calve. Most tidewater glaciers calve above sea level, which results in a tremendous impact as the iceberg strikes the water. Tidewater glaciers undergo centuries-long cycles of advance and retreat that are much less affected by the climate change than those of other glaciers.
Thermally, a temperate glacier is at melting point throughout the year, from its surface to its base. The ice of a polar glacier is always below the freezing point from the surface to its base, although the surface snowpack may experience seasonal melting. A sub-polar glacier includes both temperate and polar ice, depending on depth beneath the surface and position along the length of the glacier. In a similar way, the thermal regime of a glacier is described by its basal temperature. A cold-based glacier is below freezing at the ice-ground interface, is thus frozen to the underlying substrate. A warm-based glacier is above or at freezing at the interface, is able to slide at this contact; this contrast is thought to a large extent to govern the ability of a glacier to erode its bed, as sliding ice promotes plucking at rock from the surface below. Glaciers which are cold-based and warm-based are known as polythermal. Glaciers form where the accumulation of ice exceeds ablation. A glacier originates from a landform called'cirque' – a armchair-shaped geological feature (such as a depressio