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104-567: When deposited into fine layered mud, such evidence includes an impact depression beneath the dropstone, and indication that the mud has been squeezed up around the edges of the falling rock. Subsequent deposits of mud drape over the dropstone and its crater. Glacial dropstones, involving rocks falling out of icebergs , are one of the most common types of dropstone preserved in the geological record, particularly when deposited in low-energy deep sea or lake environments. Dropstones differ from erratics found in glacial till in that they are deposited in

208-576: A West Germanic language that originated from the Anglo-Frisian dialects brought to Britain by Germanic settlers from various parts of what is now northwest Germany and the northern Netherlands. The resident population at this time was generally speaking Common Brittonic —the insular variety of Continental Celtic , which was influenced by the Roman occupation. This group of languages ( Welsh , Cornish , Cumbric ) cohabited alongside English into

312-424: A cirque landform (alternatively known as a corrie or as a cwm ) – a typically armchair-shaped geological feature (such as a depression between mountains enclosed by arêtes ) – which collects and compresses through gravity the snow that falls into it. This snow accumulates and the weight of the snow falling above compacts it, forming névé (granular snow). Further crushing of the individual snowflakes and squeezing

416-471: A lake or marine environments. Dropstones may also be deposited by a variety of non-glacial means. There are five natural mechanisms that produce dropstones: As glaciers move across a surface, they pluck rocks from it, and incorporate them into their mass. At the coast, fragments of glacier detach and float away as icebergs, which are often transported ( ice rafted ) many miles into the ocean, where they melt and deposit their load. When entrained rocks sink to

520-559: A century as Received Pronunciation (RP). However, due to language evolution and changing social trends, some linguists argue that RP is losing prestige or has been replaced by another accent, one that the linguist Geoff Lindsey for instance calls Standard Southern British English. Others suggest that more regionally-oriented standard accents are emerging in England. Even in Scotland and Northern Ireland, RP exerts little influence in

624-522: A glacier is usually assessed by determining the glacier mass balance or observing terminus behavior. Healthy glaciers have large accumulation zones, more than 60% of their area is snow-covered at the end of the melt season, and they have a terminus with a vigorous flow. Following the Little Ice Age 's end around 1850, glaciers around the Earth have retreated substantially . A slight cooling led to

728-601: A glacier may flow into a body of water, it forms only on land and is 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 (also known as "continental glaciers") in the polar regions , but glaciers may be found in mountain ranges on every continent other than the Australian mainland, including Oceania's high-latitude oceanic island countries such as New Zealand . Between latitudes 35°N and 35°S, glaciers occur only in

832-411: A glacier via moulins . Streams within or beneath a glacier flow in englacial or sub-glacial tunnels. These tunnels sometimes reemerge at the glacier's surface. Most of the important processes controlling glacial motion occur in the ice-bed contact—even though it is only a few meters thick. The bed's temperature, roughness and softness define basal shear stress, which in turn defines whether movement of

936-508: A greater movement, normally [əʊ], [əʉ] or [əɨ]. Dropping a morphological grammatical number , in collective nouns , is stronger in British English than North American English. This is to treat them as plural when once grammatically singular, a perceived natural number prevails, especially when applying to institutional nouns and groups of people. The noun 'police', for example, undergoes this treatment: Police are investigating

1040-408: A kilometer per year. Eventually, the ice will be surging fast enough that it begins to thin, as accumulation cannot keep up with the transport. This thinning will increase the conductive heat loss, slowing the glacier and causing freezing. This freezing will slow the glacier further, often until it is stationary, whence the cycle can begin again. The flow of water under the glacial surface can have

1144-404: A large effect on the motion of the glacier itself. Subglacial lakes contain significant amounts of water, which can move fast: cubic kilometers can be transported between lakes over the course of a couple of years. This motion is thought to occur in two main modes: pipe flow involves liquid water moving through pipe-like conduits, like a sub-glacial river; sheet flow involves motion of water in

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1248-406: A lesser class or social status and often discounted or considered of a low intelligence. Another contribution to the standardisation of British English was the introduction of the printing press to England in the mid-15th century. In doing so, William Caxton enabled a common language and spelling to be dispersed among the entirety of England at a much faster rate. Samuel Johnson's A Dictionary of

1352-460: A lower heat conductance, meaning that the basal temperature is also likely to be higher. Bed temperature tends to vary in a cyclic fashion. A cool bed has a high strength, reducing the speed of the glacier. This increases the rate of accumulation, since newly fallen snow is not transported away. Consequently, the glacier thickens, with three consequences: firstly, the bed is better insulated, allowing greater retention of geothermal heat. Secondly,

1456-659: A process called T-glottalisation . National media, being based in London, have seen the glottal stop spreading more widely than it once was in word endings, not being heard as "no [ʔ] " and bottle of water being heard as "bo [ʔ] le of wa [ʔ] er". It is still stigmatised when used at the beginning and central positions, such as later , while often has all but regained /t/ . Other consonants subject to this usage in Cockney English are p , as in pa [ʔ] er and k as in ba [ʔ] er. In most areas of England and Wales, outside

1560-542: A raft of floating plant material or in the roots of floating trees. When such a raft disintegrates due to waterlogging and sinking of its constituents, the transported rocks would also sink. Dropstones formed in this manner are typically associated with organic matter, especially logs – the fossilised remains of the raft that caused its transport. Vertebrates, including ancient dinosaurs, may also act as dropstone agents by ingesting gastroliths and depositing them on land or within standing bodies of water by regurgitation or when

1664-520: A regional accent or dialect. However, about 2% of Britons speak with an accent called Received Pronunciation (also called "the King's English", "Oxford English" and " BBC English" ), that is essentially region-less. It derives from a mixture of the Midlands and Southern dialects spoken in London in the early modern period. It is frequently used as a model for teaching English to foreign learners. In

1768-488: A thin layer. A switch between the two flow conditions may be associated with surging behavior. Indeed, the loss of sub-glacial water supply has been linked with the shut-down of ice movement in the Kamb ice stream. The subglacial motion of water is expressed in the surface topography of ice sheets, which slump down into vacated subglacial lakes. The speed of glacial displacement is partly determined by friction . Friction makes

1872-410: 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 climate change than other glaciers. Thermally, a temperate glacier is at a melting point throughout the year, from its surface to its base. The ice of a polar glacier is always below the freezing threshold from the surface to its base, although

1976-468: Is a persistent body of dense ice that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries . It acquires distinguishing features, such as crevasses and seracs , as it slowly flows and deforms under stresses induced by its weight. As it moves, it abrades rock and debris from its substrate to create landforms such as cirques , moraines , or fjords . Although

2080-456: Is above or at freezing at the interface and is able to slide at this contact. This contrast is thought to a large extent to govern the ability of a glacier to effectively erode its bed , as sliding ice promotes plucking at rock from the surface below. Glaciers which are partly cold-based and partly warm-based are known as polythermal . Glaciers form where the accumulation of snow and ice exceeds ablation . A glacier usually originates from

2184-407: Is affected by factors such as slope, ice thickness, snowfall, longitudinal confinement, basal temperature, meltwater production, and bed hardness. A few glaciers have periods of very rapid advancement called surges . These glaciers exhibit normal movement until suddenly they accelerate, then return to their previous movement state. These surges may be caused by the failure of the underlying bedrock,

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2288-725: Is also due to London-centric influences. Examples of R-dropping are car and sugar , where the R is not pronounced. British dialects differ on the extent of diphthongisation of long vowels, with southern varieties extensively turning them into diphthongs, and with northern dialects normally preserving many of them. As a comparison, North American varieties could be said to be in-between. Long vowels /iː/ and /uː/ are usually preserved, and in several areas also /oː/ and /eː/, as in go and say (unlike other varieties of English, that change them to [oʊ] and [eɪ] respectively). Some areas go as far as not diphthongising medieval /iː/ and /uː/, that give rise to modern /aɪ/ and /aʊ/; that is, for example, in

2392-411: Is because these peaks are located near or in the hyperarid Atacama Desert . Glaciers erode terrain through two principal processes: plucking and abrasion . As glaciers flow over bedrock, they soften and lift blocks of rock into the ice. This process, called plucking, is caused by subglacial water that penetrates fractures in the bedrock and subsequently freezes and expands. This expansion causes

2496-406: Is by basal sliding, where meltwater forms between the ice and the bed itself. Whether a bed is hard or soft depends on the porosity and pore pressure; higher porosity decreases the sediment strength (thus increases the shear stress τ B ). Porosity may vary through a range of methods. Bed softness may vary in space or time, and changes dramatically from glacier to glacier. An important factor

2600-434: Is called glaciology . Glaciers are important components of the global cryosphere . Glaciers are categorized by their morphology, thermal characteristics, and behavior. Alpine glaciers form on the crests and 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

2704-416: Is called rock flour and is made up of rock grains between 0.002 and 0.00625 mm in size. Abrasion leads to steeper valley walls and mountain slopes in alpine settings, which can cause avalanches and rock slides, which add even more material to the glacier. Glacial abrasion is commonly characterized by glacial striations . Glaciers produce these when they contain large boulders that carve long scratches in

2808-647: Is higher, and the mountains above 5,000 m (16,400 ft) usually have permanent snow. Even at high latitudes, glacier formation is not inevitable. Areas of the Arctic , such as Banks Island , and the McMurdo Dry Valleys in Antarctica are considered polar deserts where glaciers cannot form because they receive little snowfall despite the bitter cold. Cold air, unlike warm air, is unable to transport much water vapor. Even during glacial periods of

2912-795: Is included in style guides issued by various publishers including The Times newspaper, the Oxford University Press and the Cambridge University Press . The Oxford University Press guidelines were originally drafted as a single broadsheet page by Horace Henry Hart, and were at the time (1893) the first guide of their type in English; they were gradually expanded and eventually published, first as Hart's Rules , and in 2002 as part of The Oxford Manual of Style . Comparable in authority and stature to The Chicago Manual of Style for published American English ,

3016-897: Is termed an ice cap or ice field . Ice caps have an area less than 50,000 km (19,000 sq mi) by definition. Glacial bodies larger than 50,000 km (19,000 sq mi) are called ice sheets or 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 Antarctica and Greenland. They contain vast quantities of freshwater, enough that if both melted, global sea levels would rise by over 70 m (230 ft). Portions of an ice sheet or cap that extend into water are called ice shelves ; they tend to be thin with limited slopes and reduced velocities. 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

3120-413: Is the region where there is a net loss in glacier mass. The upper part of a glacier, where accumulation exceeds ablation, is called the accumulation zone . The equilibrium line separates the ablation zone and the accumulation zone; it is the contour where the amount of new snow gained by accumulation is equal to the amount of ice lost through ablation. In general, the accumulation zone accounts for 60–70% of

3224-402: Is the underlying geology; glacial speeds tend to differ more when they change bedrock than when the gradient changes. Further, bed roughness can also act to slow glacial motion. The roughness of the bed is a measure of how many boulders and obstacles protrude into the overlying ice. Ice flows around these obstacles by melting under the high pressure on their stoss side ; the resultant meltwater

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3328-552: Is then forced into the cavity arising in their lee side , where it re-freezes. As well as affecting the sediment stress, fluid pressure (p w ) can affect the friction between the glacier and the bed. High fluid pressure provides a buoyancy force upwards on the glacier, reducing the friction at its base. The fluid pressure is compared to the ice overburden pressure, p i , given by ρgh. Under fast-flowing ice streams, these two pressures will be approximately equal, with an effective pressure (p i – p w ) of 30 kPa; i.e. all of

3432-547: The Chambers Dictionary , and the Collins Dictionary record actual usage rather than attempting to prescribe it. In addition, vocabulary and usage change with time; words are freely borrowed from other languages and other varieties of English, and neologisms are frequent. For historical reasons dating back to the rise of London in the ninth century, the form of language spoken in London and

3536-993: The Andes , the Himalayas , the Rocky Mountains , the Caucasus , Scandinavian Mountains , and the Alps . Snezhnika glacier in Pirin Mountain, Bulgaria with a latitude of 41°46′09″ N is the southernmost glacial mass in Europe. Mainland Australia currently contains no glaciers, although a small glacier on Mount Kosciuszko was present in the last glacial period . In New Guinea, small, rapidly diminishing, glaciers are located on Puncak Jaya . Africa has glaciers on Mount Kilimanjaro in Tanzania, on Mount Kenya , and in

3640-658: The East Midlands became standard English within the Court, and ultimately became the basis for generally accepted use in the law, government, literature and education in Britain. The standardisation of British English is thought to be from both dialect levelling and a thought of social superiority. Speaking in the Standard dialect created class distinctions; those who did not speak the standard English would be considered of

3744-599: The English language native to the United Kingdom of Great Britain and Northern Ireland . More narrowly, it can refer specifically to the English language in England , or, more broadly, to the collective dialects of English throughout the British Isles taken as a single umbrella variety, for instance additionally incorporating Scottish English , Welsh English , and Northern Irish English . Tom McArthur in

3848-644: The Faroe and Crozet Islands were completely glaciated. The permanent snow cover necessary for glacier formation is affected by factors such as the degree of slope on the land, amount of snowfall and the winds. Glaciers can be found in all latitudes except from 20° to 27° north and south of the equator where the presence of the descending limb of the Hadley circulation lowers precipitation so much that with high insolation snow lines reach above 6,500 m (21,330 ft). Between 19˚N and 19˚S, however, precipitation

3952-760: The Himalayas , Andes , and a few high mountains in East Africa, Mexico, New Guinea and on Zard-Kuh in Iran. With more than 7,000 known glaciers, Pakistan has more glacial ice than any other country outside the polar regions. Glaciers cover about 10% of Earth's land surface. Continental glaciers cover nearly 13 million km (5 million sq mi) or about 98% of Antarctica 's 13.2 million km (5.1 million sq mi), with an average thickness of ice 2,100 m (7,000 ft). Greenland and Patagonia also have huge expanses of continental glaciers. The volume of glaciers, not including

4056-644: The Oxford Guide to World English acknowledges that British English shares "all the ambiguities and tensions [with] the word 'British' and as a result can be used and interpreted in two ways, more broadly or more narrowly, within a range of blurring and ambiguity". Variations exist in formal (both written and spoken) English in the United Kingdom. For example, the adjective wee is almost exclusively used in parts of Scotland, north-east England, Northern Ireland, Ireland, and occasionally Yorkshire , whereas

4160-562: The Quaternary , Manchuria , lowland Siberia , and central and northern Alaska , though extraordinarily cold, had such light snowfall that glaciers could not form. In addition to the dry, unglaciated polar regions, some mountains and volcanoes in Bolivia, Chile and Argentina are high (4,500 to 6,900 m or 14,800 to 22,600 ft) and cold, but the relative lack of precipitation prevents snow from accumulating into glaciers. This

4264-493: The Royal Spanish Academy with Spanish. Standard British English differs notably in certain vocabulary, grammar, and pronunciation features from standard American English and certain other standard English varieties around the world. British and American spelling also differ in minor ways. The accent, or pronunciation system, of standard British English, based in southeastern England, has been known for over

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4368-535: The Rwenzori Mountains . Oceanic islands with glaciers include Iceland, several of the islands off the coast of Norway including Svalbard and Jan Mayen to the far north, New Zealand and the subantarctic islands of Marion , Heard , Grande Terre (Kerguelen) and Bouvet . During glacial periods of the Quaternary, Taiwan , Hawaii on Mauna Kea and Tenerife also had large alpine glaciers, while

4472-490: The Scots language or Scottish Gaelic ). Each group includes a range of dialects, some markedly different from others. The various British dialects also differ in the words that they have borrowed from other languages. Around the middle of the 15th century, there were points where within the 5 major dialects there were almost 500 ways to spell the word though . Following its last major survey of English Dialects (1949–1950),

4576-573: The University of Leeds has started work on a new project. In May 2007 the Arts and Humanities Research Council awarded a grant to Leeds to study British regional dialects. The team are sifting through a large collection of examples of regional slang words and phrases turned up by the "Voices project" run by the BBC , in which they invited the public to send in examples of English still spoken throughout

4680-610: The West Country and other near-by counties of the UK, the consonant R is not pronounced if not followed by a vowel, lengthening the preceding vowel instead. This phenomenon is known as non-rhoticity . In these same areas, a tendency exists to insert an R between a word ending in a vowel and a next word beginning with a vowel. This is called the intrusive R . It could be understood as a merger, in that words that once ended in an R and words that did not are no longer treated differently. This

4784-448: The 1990s and 2000s. In a study using data from January 1993 through October 2005, more events were detected every year since 2002, and twice as many events were recorded in 2005 as there were in any other year. Ogives or Forbes bands are alternating wave crests and valleys that appear as dark and light bands of ice on glacier surfaces. They are linked to seasonal motion of glaciers; the width of one dark and one light band generally equals

4888-629: The 21st century. RP, while long established as the standard English accent around the globe due to the spread of the British Empire , is distinct from the standard English pronunciation in some parts of the world; most prominently, RP notably contrasts with standard North American accents. In the 21st century, dictionaries like the Oxford English Dictionary , the Longman Dictionary of Contemporary English ,

4992-836: The English Language (1755) was a large step in the English-language spelling reform , where the purification of language focused on standardising both speech and spelling. By the early 20th century, British authors had produced numerous books intended as guides to English grammar and usage, a few of which achieved sufficient acclaim to have remained in print for long periods and to have been reissued in new editions after some decades. These include, most notably of all, Fowler's Modern English Usage and The Complete Plain Words by Sir Ernest Gowers . Detailed guidance on many aspects of writing British English for publication

5096-666: The Germanic schwein ) is the animal in the field bred by the occupied Anglo-Saxons and pork (like the French porc ) is the animal at the table eaten by the occupying Normans. Another example is the Anglo-Saxon cu meaning cow, and the French bœuf meaning beef. Cohabitation with the Scandinavians resulted in a significant grammatical simplification and lexical enrichment of the Anglo-Frisian core of English;

5200-922: The Oxford Manual is a fairly exhaustive standard for published British English that writers can turn to in the absence of specific guidance from their publishing house. British English is the basis of, and very similar to, Commonwealth English . Commonwealth English is English as spoken and written in the Commonwealth countries , though often with some local variation. This includes English spoken in Australia , Malta , New Zealand , Nigeria , and South Africa . It also includes South Asian English used in South Asia, in English varieties in Southeast Asia , and in parts of Africa. Canadian English

5304-712: The South East, there are significantly different accents; the Cockney accent spoken by some East Londoners is strikingly different from Received Pronunciation (RP). Cockney rhyming slang can be (and was initially intended to be) difficult for outsiders to understand, although the extent of its use is often somewhat exaggerated. Londoners speak with a mixture of accents, depending on ethnicity, neighbourhood, class, age, upbringing, and sundry other factors. Estuary English has been gaining prominence in recent decades: it has some features of RP and some of Cockney. Immigrants to

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5408-550: The UK in recent decades have brought many more languages to the country and particularly to London. Surveys started in 1979 by the Inner London Education Authority discovered over 125 languages being spoken domestically by the families of the inner city's schoolchildren. Notably Multicultural London English , a sociolect that emerged in the late 20th century spoken mainly by young, working-class people in multicultural parts of London . Since

5512-576: The United Kingdom , as well as within the countries themselves. The major divisions are normally classified as English English (or English as spoken in England (which is itself broadly grouped into Southern English , West Country , East and West Midlands English and Northern English ), Northern Irish English (in Northern Ireland), Welsh English (not to be confused with the Welsh language ), and Scottish English (not to be confused with

5616-465: The West Scottish accent. Phonological features characteristic of British English revolve around the pronunciation of the letter R, as well as the dental plosive T and some diphthongs specific to this dialect. Once regarded as a Cockney feature, in a number of forms of spoken British English, /t/ has become commonly realised as a glottal stop [ʔ] when it is in the intervocalic position, in

5720-466: The action of strong ocean-floor turbidity currents . Boulders the size of a human have been found in relatively recent finely laminated sediments near Jamaica , which has been a warm tropical island entirely devoid of glaciers since it came into existence. Whilst turbidity currents are cited as the origin of the boulders, they are not found in association with deposits formed by them. Stones can also be transported large distances by becoming bound in

5824-410: The adjective little is predominant elsewhere. Nevertheless, there is a meaningful degree of uniformity in written English within the United Kingdom, and this could be described by the term British English . The forms of spoken English, however, vary considerably more than in most other areas of the world where English is spoken and so a uniform concept of British English is more difficult to apply to

5928-412: The advance of many alpine glaciers between 1950 and 1985, but since 1985 glacier retreat and mass loss has become larger and increasingly ubiquitous. Glaciers move downhill by the force of gravity and the internal deformation of ice. At the molecular level, ice consists of stacked layers of molecules with relatively weak bonds between layers. When the amount of strain (deformation) is proportional to

6032-520: The air from the snow turns it into "glacial ice". This glacial ice will fill the cirque until it "overflows" through a geological weakness or vacancy, such as a gap between two mountains. When the mass of snow and ice reaches sufficient thickness, it begins to move by a combination of surface slope, gravity, and pressure. On steeper slopes, this can occur with as little as 15 m (49 ft) of snow-ice. In temperate glaciers, snow repeatedly freezes and thaws, changing into granular ice called firn . Under

6136-430: The amount of melting at surface of the glacier, the faster the ice will flow. Basal sliding is dominant in temperate or warm-based glaciers. The presence of basal meltwater depends on both bed temperature and other factors. For instance, the melting point of water decreases under pressure, meaning that water melts at a lower temperature under thicker glaciers. This acts as a "double whammy", because thicker glaciers have

6240-713: The annual movement of the glacier. Ogives are formed when ice from an icefall is severely broken up, increasing ablation surface area during summer. This creates a swale and space for snow accumulation in the winter, which in turn creates a ridge. Sometimes ogives consist only of undulations or color bands and are described as wave ogives or band ogives. Glaciers are present on every continent and in approximately fifty countries, excluding those (Australia, South Africa) that have glaciers only on distant subantarctic island territories. Extensive glaciers are found in Antarctica, Argentina, Chile, Canada, Pakistan, Alaska, Greenland and Iceland. Mountain glaciers are widespread, especially in

6344-488: The award of the grant in 2007, Leeds University stated: that they were "very pleased"—and indeed, "well chuffed"—at receiving their generous grant. He could, of course, have been "bostin" if he had come from the Black Country , or if he was a Scouser he would have been well "made up" over so many spondoolicks, because as a Geordie might say, £460,000 is a "canny load of chink". Most people in Britain speak with

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6448-432: The bedrock has frequent fractures on the surface, glacial erosion rates tend to increase as plucking is the main erosive force on the surface; when the bedrock has wide gaps between sporadic fractures, however, abrasion tends to be the dominant erosive form and glacial erosion rates become slow. Glaciers in lower latitudes tend to be much more erosive than glaciers in higher latitudes, because they have more meltwater reaching

6552-445: The bedrock. By mapping the direction of the striations, researchers can determine the direction of the glacier's movement. Similar to striations are chatter marks , lines of crescent-shape depressions in the rock underlying a glacier. They are formed by abrasion when boulders in the glacier are repeatedly caught and released as they are dragged along the bedrock. The rate of glacier erosion varies. Six factors control erosion rate: When

6656-622: The country. The BBC Voices project also collected hundreds of news articles about how the British speak English from swearing through to items on language schools. This information will also be collated and analysed by Johnson's team both for content and for where it was reported. "Perhaps the most remarkable finding in the Voices study is that the English language is as diverse as ever, despite our increased mobility and constant exposure to other accents and dialects through TV and radio". When discussing

6760-571: The created ice's density. 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 , and ultimately Latin glaciēs , meaning "ice". The processes and features caused by or related to glaciers are referred to as glacial. The process of glacier establishment, growth and flow is called glaciation . The corresponding area of study

6864-467: The deep profile of fjords , which can reach a kilometer in depth as ice is topographically steered into them. The extension of fjords inland increases the rate of ice sheet thinning since they are the principal conduits for draining ice sheets. It also makes the ice sheets more sensitive to changes in climate and the ocean. Although evidence in favor of glacial flow was known by the early 19th century, other theories of glacial motion were advanced, such as

6968-483: The deformation to become a plastic flow rather than elastic. Then, the glacier will begin to deform under its own weight and flow across the landscape. According to the Glen–Nye flow law , the relationship between stress and strain, and thus the rate of internal flow, can be modeled as follows: where: The lowest velocities are near the base of the glacier and along valley sides where friction acts against flow, causing

7072-681: The dinosaur era sediments are debated among scholars as to their origin - gastroliths(i.e.,biological dropstones) or ancient, strange river sediments. Meteorites landing in marine depositional environments are a fifth category of dropstone. A number of meteorites have been found in Sweden's Thorsberg quarry, where they sank to the bottom of a shallow sea and were entombed in limestone 470 million years ago. [REDACTED] Media related to Dropstones at Wikimedia Commons Glacier A glacier ( US : / ˈ ɡ l eɪ ʃ ər / ; UK : / ˈ ɡ l æ s i ər , ˈ ɡ l eɪ s i ər / )

7176-418: The essentially correct explanation in the 1840s, although it was several decades before it was fully accepted. The top 50 m (160 ft) of a glacier are rigid because they are under low pressure . This upper section is known as the fracture zone and moves mostly as a single unit over the plastic-flowing lower section. When a glacier moves through irregular terrain, cracks called crevasses develop in

7280-553: The force of an eruption. If these land in fine sediments or pumice-forming ash, they can form dropstones. Dropstones originating in this fashion are relatively rare in the geological record as most will land on high ground, which has a poor preservation potential as it is in an erosive environment. However, a large blast may spread bombs far enough for them to end up in a marine setting of fine enough sediment for them to be recognized, or may land in or be buried by pyroclastic flows and surges . Dropstones can also be deposited through

7384-475: The fracture zone. Crevasses form because of differences in glacier velocity. If two rigid sections of a glacier move at different speeds or directions, shear forces cause them to break apart, opening a crevasse. Crevasses are seldom more than 46 m (150 ft) deep but, in some cases, can be at least 300 m (1,000 ft) deep. Beneath this point, the plasticity of the ice prevents the formation of cracks. Intersecting crevasses can create isolated peaks in

7488-403: The glacial base and facilitate sediment production and transport under the same moving speed and amount of ice. Material that becomes incorporated in a glacier is typically carried as far as the zone of ablation before being deposited. Glacial deposits are of two distinct types: British English British English (abbreviations: BrE , en-GB , and BE ) is the set of varieties of

7592-453: The glacier to melt, creating a water source that is especially important for plants, animals and human uses when other sources may be scant. However, within high-altitude and Antarctic environments, the seasonal temperature difference is often not sufficient to release meltwater. Since glacial mass is affected by long-term climatic changes, e.g., precipitation , mean temperature , and cloud cover , glacial mass changes are considered among

7696-428: The glacier will be accommodated by motion in the sediments, or if it'll be able to slide. A soft bed, with high porosity and low pore fluid pressure, allows the glacier to move by sediment sliding: the base of the glacier may even remain frozen to the bed, where the underlying sediment slips underneath it like a tube of toothpaste. A hard bed cannot deform in this way; therefore the only way for hard-based glaciers to move

7800-510: The glacier's surface area, more if the glacier calves icebergs. Ice in the accumulation zone is deep enough to exert a downward force that erodes underlying rock. After a glacier melts, it often leaves behind a bowl- or amphitheater-shaped depression that ranges in size from large basins like the Great Lakes to smaller mountain depressions known as cirques . The accumulation zone can be subdivided based on its melt conditions. The health of

7904-619: The ice at the bottom of the glacier move more slowly than ice at the top. In alpine glaciers, friction is also generated at the valley's sidewalls, which slows the edges relative to the center. Mean glacial speed varies greatly but is typically around 1 m (3 ft) per day. There may be no motion in stagnant areas; for example, in parts of Alaska, trees can establish themselves on surface sediment deposits. In other cases, glaciers can move as fast as 20–30 m (70–100 ft) per day, such as in Greenland's Jakobshavn Isbræ . Glacial speed

8008-420: The ice sheets of Antarctica and Greenland, has been estimated at 170,000 km . Glacial ice is the largest reservoir of fresh water on Earth, holding with ice sheets about 69 percent of the world's freshwater. Many glaciers from temperate , alpine and seasonal polar climates store water as ice during the colder seasons and release it later in the form of meltwater as warmer summer temperatures cause

8112-556: The ice to act as a lever that loosens the rock by lifting it. Thus, sediments of all sizes become part of the glacier's load. If a retreating glacier gains enough debris, it may become a rock glacier , like the Timpanogos Glacier in Utah. Abrasion occurs when the ice and its load of rock fragments slide over bedrock and function as sandpaper, smoothing and polishing the bedrock below. The pulverized rock this process produces

8216-488: The ice, called seracs . Crevasses can form in several different ways. Transverse crevasses are transverse to flow and form where steeper slopes cause a glacier to accelerate. Longitudinal crevasses form semi-parallel to flow where a glacier expands laterally. Marginal crevasses form near the edge of the glacier, caused by the reduction in speed caused by friction of the valley walls. Marginal crevasses are largely transverse to flow. Moving glacier ice can sometimes separate from

8320-458: The idea of two different morphemes, one that causes the double negation, and one that is used for the point or the verb. Standard English in the United Kingdom, as in other English-speaking nations, is widely enforced in schools and by social norms for formal contexts but not by any singular authority; for instance, there is no institution equivalent to the Académie française with French or

8424-411: The idea that meltwater, refreezing inside glaciers, caused the glacier to dilate and extend its length. As it became clear that glaciers behaved to some degree as if the ice were a viscous fluid, it was argued that "regelation", or the melting and refreezing of ice at a temperature lowered by the pressure on the ice inside the glacier, was what allowed the ice to deform and flow. James Forbes came up with

8528-418: The increased pressure can facilitate melting. Most importantly, τ D is increased. These factors will combine to accelerate the glacier. As friction increases with the square of velocity, faster motion will greatly increase frictional heating, with ensuing melting – which causes a positive feedback, increasing ice speed to a faster flow rate still: west Antarctic glaciers are known to reach velocities of up to

8632-423: The infrared OH stretching mode of the water molecule. (Liquid water appears blue for the same reason. The blue of glacier ice is sometimes misattributed to Rayleigh scattering of bubbles in the ice.) A glacier originates at a location called its glacier head and terminates at its glacier foot, snout, or terminus . Glaciers are broken into zones based on surface snowpack and melt conditions. The ablation zone

8736-523: The last southern Midlands accent to use the broad "a" in words like bath or grass (i.e. barth or grarss ). Conversely crass or plastic use a slender "a". A few miles northwest in Leicestershire the slender "a" becomes more widespread generally. In the town of Corby , five miles (8 km) north, one can find Corbyite which, unlike the Kettering accent, is largely influenced by

8840-518: The later Norman occupation led to the grafting onto that Germanic core of a more elaborate layer of words from the Romance branch of the European languages. This Norman influence entered English largely through the courts and government. Thus, English developed into a "borrowing" language of great flexibility and with a huge vocabulary . Dialects and accents vary amongst the four countries of

8944-457: The mass internal migration to Northamptonshire in the 1940s and given its position between several major accent regions, it has become a source of various accent developments. In Northampton the older accent has been influenced by overspill Londoners. There is an accent known locally as the Kettering accent, which is a transitional accent between the East Midlands and East Anglian . It is

9048-463: The modern period, but due to their remoteness from the Germanic languages , influence on English was notably limited . However, the degree of influence remains debated, and it has recently been argued that its grammatical influence accounts for the substantial innovations noted between English and the other West Germanic languages. Initially, Old English was a diverse group of dialects, reflecting

9152-679: The most deformation. Velocity increases inward toward the center line and upward, as the amount of deformation decreases. The highest flow velocities are found at the surface, representing the sum of the velocities of all the layers below. Because ice can flow faster where it is thicker, the rate of glacier-induced erosion is directly proportional to the thickness of overlying ice. Consequently, pre-glacial low hollows will be deepened and pre-existing topography will be amplified by glacial action, while nunataks , which protrude above ice sheets, barely erode at all – erosion has been estimated as 5 m per 1.2 million years. This explains, for example,

9256-445: 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 , because water molecules absorb other colors more efficiently than blue. 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

9360-455: The ocean floor, they can be incorporated into the oceanic sediments, which are typically fine grained. Glacially deposited rock differing from the size and type of rock native to the area in which it rests is called a glacial erratic . Whilst dropstones were once thought to be diagnostic of glaciers, it has since been realised that they can also be formed via volcanic eruptions. Volcanic bombs are large fragments of rock, projected many miles by

9464-410: The organism dies. These rock clasts, usually siliceous, are anomalous compared to the eventual surrounding rocks, and are much more easily preserved than the bones and other organic material of the biological organism that deposited them. There are over 10 known examples of dinosaur remains actually with associated "dropstones", sometimes with as many as 200 clasts. And many other rounded clasts in some of

9568-725: The pooling of meltwater at the base of the glacier  — perhaps delivered from a supraglacial lake  — or the simple accumulation of mass beyond a critical "tipping point". Temporary rates up to 90 m (300 ft) per day have occurred when increased temperature or overlying pressure caused bottom ice to melt and water to accumulate beneath a glacier. In glaciated areas where the glacier moves faster than one km per year, glacial earthquakes occur. These are large scale earthquakes that have seismic magnitudes as high as 6.1. The number of glacial earthquakes in Greenland peaks every year in July, August, and September and increased rapidly in

9672-410: The pressure of the layers of ice and snow above it, this granular ice fuses into denser firn. Over a period of years, layers of firn undergo further compaction and become glacial ice. Glacier ice is slightly more dense than ice formed from frozen water because glacier ice contains fewer trapped air bubbles. Glacial ice has a distinctive blue tint because it absorbs some red light due to an overtone of

9776-567: The sea, often with an ice tongue , like Mertz Glacier . Tidewater glaciers are glaciers that terminate in the sea, including most glaciers flowing from Greenland, Antarctica, Baffin , Devon , and Ellesmere Islands in Canada, Southeast Alaska , and the Northern and Southern Patagonian Ice Fields . As the ice reaches the sea, pieces break off or calve, forming icebergs . Most tidewater glaciers calve above sea level, which often results in

9880-401: The spoken language. Globally, countries that are former British colonies or members of the Commonwealth tend to follow British English, as is the case for English used by European Union institutions. In China, both British English and American English are taught. The UK government actively teaches and promotes English around the world and operates in over 200 countries . English is

9984-409: The stagnant ice above, forming a bergschrund . Bergschrunds resemble crevasses but are singular features at a glacier's margins. Crevasses make travel over glaciers hazardous, especially when they are hidden by fragile snow bridges . Below the equilibrium line, glacial meltwater is concentrated in stream channels. Meltwater can pool in proglacial lakes on top of a glacier or descend into the depths of

10088-423: The stress being applied, ice will act as an elastic solid. Ice needs to be at least 30 m (98 ft) thick to even start flowing, but once its thickness exceeds about 50 m (160 ft) (160 ft), stress on the layer above will exceeds the inter-layer binding strength, and then it'll move faster than the layer below. This means that small amounts of stress can result in a large amount of strain, causing

10192-438: The surface snowpack may experience seasonal melting. A subpolar glacier includes both temperate and polar ice, depending on the depth beneath the surface and position along the length of the glacier. In a similar way, the thermal regime of a glacier is often described by its basal temperature. A cold-based glacier is below freezing at the ice-ground interface and is thus frozen to the underlying substrate. A warm-based glacier

10296-603: The theft of work tools worth £500 from a van at the Sprucefield park and ride car park in Lisburn. A football team can be treated likewise: Arsenal have lost just one of 20 home Premier League matches against Manchester City. This tendency can be observed in texts produced already in the 19th century. For example, Jane Austen , a British author, writes in Chapter 4 of Pride and Prejudice , published in 1813: All

10400-403: The traditional accent of Newcastle upon Tyne , 'out' will sound as 'oot', and in parts of Scotland and North-West England, 'my' will be pronounced as 'me'. Long vowels /iː/ and /uː/ are diphthongised to [ɪi] and [ʊu] respectively (or, more technically, [ʏʉ], with a raised tongue), so that ee and oo in feed and food are pronounced with a movement. The diphthong [oʊ] is also pronounced with

10504-750: The varied origins of the Anglo-Saxon kingdoms of England. One of these dialects, Late West Saxon , eventually came to dominate. The original Old English was then influenced by two waves of invasion: the first was by speakers of the Scandinavian branch of the Germanic family, who settled in parts of Britain in the eighth and ninth centuries; the second was the Normans in the 11th century, who spoke Old Norman and ultimately developed an English variety of this called Anglo-Norman . These two invasions caused English to become "mixed" to some degree (though it

10608-417: The weight of the ice is supported by the underlying water, and the glacier is afloat. Glaciers may also move by basal sliding , where the base of the glacier is lubricated by the presence of liquid water, reducing basal shear stress and allowing the glacier to slide over the terrain on which it sits. Meltwater may be produced by pressure-induced melting, friction or geothermal heat . The more variable

10712-568: The world are good and agreeable in your eyes. However, in Chapter 16, the grammatical number is used. The world is blinded by his fortune and consequence. Some dialects of British English use negative concords, also known as double negatives . Rather than changing a word or using a positive, words like nobody, not, nothing, and never would be used in the same sentence. While this does not occur in Standard English, it does occur in non-standard dialects. The double negation follows

10816-422: Was never a truly mixed language in the strictest sense of the word; mixed languages arise from the cohabitation of speakers of different languages, who develop a hybrid tongue for basic communication). The more idiomatic, concrete and descriptive English is, the more it is from Anglo-Saxon origins. The more intellectual and abstract English is, the more it contains Latin and French influences, e.g. swine (like

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