120-600: The Archean Eon ( IPA : / ɑːr ˈ k iː ə n / ar- KEE -ən , also spelled Archaean or Archæan ), in older sources sometimes called the Archaeozoic , is the second of the four geologic eons of Earth 's history , preceded by the Hadean Eon and followed by the Proterozoic . The Archean represents the time period from 4,031 to 2,500 Mya (million years ago). The Late Heavy Bombardment
240-483: A pitch trace on a musical scale . Beyond the letters themselves, there are a variety of secondary symbols which aid in transcription. Diacritic marks can be combined with the letters to add tone and phonetic detail such as secondary articulation . There are also special symbols for prosodic features such as stress and intonation. There are two principal types of brackets used to set off (delimit) IPA transcriptions: Less common conventions include: All three of
360-532: A conflicting use to delimit prosodic transcription within the Voice Quality Symbols , which are an extension of IPA used in extIPA, but are not otherwise used in IPA proper. Other delimiters sometimes seen are pipes and double pipes taken from Americanist phonetic notation . However, these conflict with the pipes used in basic IPA prosodic transcription. Other delimiters are double slashes, –
480-798: A diameter greater than 10 kilometers (6 mi) every 15 million years. This is about the size of the Chicxulub impactor. These impacts would have been an important oxygen sink and would have caused drastic fluctuations of atmospheric oxygen levels. The Archean atmosphere is thought to have almost completely lacked free oxygen ; oxygen levels were less than 0.001% of their present atmospheric level, with some analyses suggesting they were as low as 0.00001% of modern levels. However, transient episodes of heightened oxygen concentrations are known from this eon around 2,980–2,960 Ma, 2,700 Ma, and 2,501 Ma. The pulses of increased oxygenation at 2,700 and 2,501 Ma have both been considered by some as potential start points of
600-465: A feature in later, more oxic oceans. Despite the lack of free oxygen, the rate of organic carbon burial appears to have been roughly the same as in the present. Due to extremely low oxygen levels, sulphate was rare in the Archean ocean, and sulphides were produced primarily through reduction of organically sourced sulphite or through mineralisation of compounds containing reduced sulphur. The Archean ocean
720-580: A group of French and English language teachers, led by the French linguist Paul Passy , formed what would be known from 1897 onwards as the International Phonetic Association (in French, l'Association phonétique internationale ). The idea of the alphabet had been suggested to Passy by Otto Jespersen . It was developed by Passy along with other members of the association, principally Daniel Jones . The original IPA alphabet
840-452: A mix of IPA with Americanist phonetic notation or Sinological phonetic notation or otherwise use nonstandard symbols for various reasons. Authors who employ such nonstandard use are encouraged to include a chart or other explanation of their choices, which is good practice in general, as linguists differ in their understanding of the exact meaning of IPA symbols and common conventions change over time. Many British dictionaries, including
960-476: A power source, this waterfall determined the location of Minneapolis . One tributary of the river coming from the west, Minnehaha Creek , receded only a few hundred yards from one of the channels of the Mississippi. Minnehaha Falls remains as a picturesque and informative relic of River Warren Falls, and the limestone-over-sandstone construction is readily apparent in its small gorge. At St. Anthony Falls,
1080-695: A row left out to save space. In the table below, a slightly different arrangement is made: All pulmonic consonants are included in the pulmonic-consonant table, and the vibrants and laterals are separated out so that the rows reflect the common lenition pathway of stop → fricative → approximant , as well as the fact that several letters pull double duty as both fricative and approximant; affricates may then be created by joining stops and fricatives from adjacent cells. Shaded cells represent articulations that are judged to be impossible or not distinctive. Vowel letters are also grouped in pairs—of unrounded and rounded vowel sounds—with these pairs also arranged from front on
1200-452: A variety of foreign languages. They are also taught by vocal coaches to perfect diction and improve tone quality and tuning. Opera librettos are authoritatively transcribed in IPA, such as Nico Castel 's volumes and Timothy Cheek's book Singing in Czech . Opera singers' ability to read IPA was used by the site Visual Thesaurus , which employed several opera singers "to make recordings for
1320-497: Is a fair amount of regional diversity in landforms and geological history, which in turn has affected Minnesota's settlement patterns, human history, and economic development. These diverse geological regions can be classified several ways. The classification used here principally derives from Sansome's Minnesota Underfoot: A Field Guide to Minnesota's Geology , but is also influenced by Minnesota's Geology by Ojakangas and Matsch. These authorities generally agree on areal borders, but
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#17327647703721440-527: Is a lack of extensive geological evidence for specific continents. One hypothesis is that rocks that are now in India, western Australia, and southern Africa formed a continent called Ur as of 3,100 Ma. Another hypothesis, which conflicts with the first, is that rocks from western Australia and southern Africa were assembled in a continent called Vaalbara as far back as 3,600 Ma. Archean rock makes up only about 8% of Earth's present-day continental crust;
1560-493: Is an alphabetic system of phonetic notation based primarily on the Latin script . It was devised by the International Phonetic Association in the late 19th century as a standard written representation for the sounds of speech . The IPA is used by lexicographers , foreign language students and teachers, linguists , speech–language pathologists , singers, actors, constructed language creators, and translators . The IPA
1680-476: Is an irregularly-shaped region composed of the northeasternmost part of the state north of Lake Superior, the area around Jay Cooke State Park and the Nemadji River basin southwest of Duluth, and much of the area east of U.S. Highway 53 that runs between Duluth and International Falls . Excluded are parts of the beds of glacial lakes Agassiz and Upham , the latter now occupied by the upper valley of
1800-421: Is designed for transcribing sounds (phones), not phonemes , though it is used for phonemic transcription as well. A few letters that did not indicate specific sounds have been retired (⟨ ˇ ⟩, once used for the "compound" tone of Swedish and Norwegian, and ⟨ ƞ ⟩, once used for the moraic nasal of Japanese), though one remains: ⟨ ɧ ⟩, used for the sj-sound of Swedish. When
1920-483: Is designed to represent those qualities of speech that are part of lexical (and, to a limited extent, prosodic ) sounds in oral language : phones , intonation and the separation of syllables . To represent additional qualities of speech—such as tooth gnashing , lisping , and sounds made with a cleft palate —an extended set of symbols may be used. Segments are transcribed by one or more IPA symbols of two basic types: letters and diacritics . For example,
2040-495: Is elected by the membership – for further discussion and a formal vote. Many users of the alphabet, including the leadership of the Association itself, deviate from its standardized usage. The Journal of the IPA finds it acceptable to mix IPA and extIPA symbols in consonant charts in their articles. (For instance, including the extIPA letter ⟨ 𝼆 ⟩ , rather than ⟨ ʎ̝̊ ⟩, in an illustration of
2160-532: Is evidenced by certain highly deformed gneisses produced by metamorphism of sedimentary protoliths . The moderate temperatures may reflect the presence of greater amounts of greenhouse gases than later in the Earth's history. Extensive abiotic denitrification took place on the Archean Earth, pumping the greenhouse gas nitrous oxide into the atmosphere. Alternatively, Earth's albedo may have been lower at
2280-701: Is generally coterminous with the Paleozoic Plateau Section of the Eastern Broadleaf Forest Province. The bedrock here is lower Paleozoic sedimentary rocks, with limestone and dolomite especially prevalent near the surface. It is highly dissected, and local tributaries of the Mississippi have cut deep valleys into the bedrock. It is an area of karst topography, with thin topsoils lying atop porous limestones, leading to formation of caverns and sinkholes . The last glaciation did not cover this region (halting at
2400-406: Is hypothesized to overlap with the beginning of the Archean. The Huronian glaciation occurred at the end of the eon. The Earth during the Archean was mostly a water world : there was continental crust , but much of it was under an ocean deeper than today's oceans. Except for some rare relict crystals , today's oldest continental crust dates back to the Archean. Much of the geological detail of
2520-689: Is in the watersheds of the Minnesota River , the Missouri River , and the Des Moines River . The Minnesota River lies in the bed of the glacial River Warren , a much larger torrent that drained Lake Agassiz while outlets to the north were blocked by glaciers. The Coteau des Prairies divides the Minnesota and Missouri River valleys, and is a striking landform created by the bifurcation of different lobes of glacial advance. On
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#17327647703722640-528: Is not always accessible to sight-impaired readers who rely on screen reader technology. Double angle brackets may occasionally be useful to distinguish original orthography from transliteration, or the idiosyncratic spelling of a manuscript from the normalized orthography of the language. Pipes are sometimes used instead of double angle brackets to denote the distinct allographs of a grapheme that are known as glyphs . For example, print | g | and script | ɡ | are two glyph variants of
2760-427: Is the official chart as posted at the website of the IPA. The letters chosen for the IPA are meant to harmonize with the Latin alphabet . For this reason, most letters are either Latin or Greek , or modifications thereof. Some letters are neither: for example, the letter denoting the glottal stop , ⟨ ʔ ⟩, originally had the form of a question mark with the dot removed. A few letters, such as that of
2880-665: Is the site of historic Native American quarries of catlinite, which is more commonly known as "pipestone". Another notable outcrop in the region is the Jeffers Petroglyphs , a Sioux Quartzite outcropping with numerous petroglyphs which may be up to 7000–9000 years old. Drier than most of the rest of the state, the region is a transition zone between the prairies and the Great Plains . Once rich in wetlands known as prairie potholes , 90%, or some three million acres (12,000 km²), have been drained for agriculture in
3000-515: Is undissected and essentially flat, but imperceptibly declines from about 400 meters at the southern beaches of Lake Agassiz to 335 meters along the Rainy River. There is almost no relief, except for benches or beaches where Glacial Lake Agassiz stabilized for a time before it receded to a lower level. In contrast to the lakebed, these beaches rise from the south to the north and east at a gradient of approximately 1:5000; this rise resulted from
3120-578: The Azoic age . Before the Hadean Eon was recognized, the Archean spanned Earth's early history from its formation about 4,540 million years ago until 2,500 million years ago. Instead of being based on stratigraphy , the beginning and end of the Archean Eon are defined chronometrically . The eon's lower boundary or starting point of 4,031±3 million years ago is officially recognized by
3240-724: The Big Stone Moraine , beyond Minnesota's borders into Canada and North Dakota . In the northeast, the Glacial Lake Agassiz plain transitions into the forests of the Arrowhead. The region includes the lowland portions of the Red River watershed and the western half of the Rainy River watershed within the state, at approximately the level of Lake Agassiz’ Herman Beach . In ecological terms, it includes
3360-520: The Duluth area, and south through eastern Minnesota down into what is now Kansas . The rifting stopped before the land could become two separate continents . About 100 million years later, the last volcano went quiet. The mountain-building and rifting events left areas of high relief above the low basin of the Midcontinent rift. Over the next 1,100 million years, the uplands were worn down and
3480-625: The Great Oxygenation Event , which most scholars consider to have begun in the Palaeoproterozoic ( c. 2.4 Ga ). Furthermore, oases of relatively high oxygen levels existed in some nearshore shallow marine settings by the Mesoarchean. The ocean was broadly reducing and lacked any persistent redoxcline , a water layer between oxygenated and anoxic layers with a strong redox gradient, which would become
3600-466: The Handbook recommended against their use, as cursive IPA is "harder for most people to decipher". A braille representation of the IPA for blind or visually impaired professionals and students has also been developed. The International Phonetic Alphabet is occasionally modified by the Association. After each modification, the Association provides an updated simplified presentation of the alphabet in
3720-460: The Hebrew alphabet for transcription of foreign words. Bilingual dictionaries that translate from foreign languages into Russian usually employ the IPA, but monolingual Russian dictionaries occasionally use pronunciation respelling for foreign words. The IPA is more common in bilingual dictionaries, but there are exceptions here too. Mass-market bilingual Czech dictionaries, for instance, tend to use
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3840-570: The IPA extensions . In the IPA itself, however, only lower-case letters are used. The 1949 edition of the IPA handbook indicated that an asterisk ⟨*⟩ might be prefixed to indicate that a word was a proper name, but this convention was not included in the 1999 Handbook , which notes the contrary use of the asterisk as a placeholder for a sound or feature that does not have a symbol. The IPA has widespread use among classical singers during preparation as they are frequently required to sing in
3960-477: The International Commission on Stratigraphy , which is the age of the oldest known intact rock formations on Earth. Evidence of rocks from the preceding Hadean Eon are therefore restricted by definition to non-rock and non-terrestrial sources such as individual mineral grains and lunar samples. When the Archean began, the Earth's heat flow was nearly three times as high as it is today, and it
4080-650: The Mount Simon Sandstone at the bottom of the sequence of sedimentary rocks to the Maquoketa Group at the top. In the Quaternary Period starting about two million years ago, glaciers expanded and retreated across the region. The ice retreated for the last time about 12,500 years ago. Melting glaciers formed many of the state's lakes and etched its river valleys. They also formed a number of proglacial lakes , which contributed to
4200-792: The Oxford English Dictionary and some learner's dictionaries such as the Oxford Advanced Learner's Dictionary and the Cambridge Advanced Learner's Dictionary , now use the International Phonetic Alphabet to represent the pronunciation of words. However, most American (and some British) volumes use one of a variety of pronunciation respelling systems, intended to be more comfortable for readers of English and to be more acceptable across dialects, without
4320-921: The Saint Louis River and its tributary the Cloquet . This area is coextensive with the Northern Superior Uplands Section of the Laurentian Mixed Forest . Known as the Arrowhead for its shape, this region shows the most visible evidence of the state's violent past. There are surface exposures of rocks first formed in volcanic activity some 2,700 mya during construction of the Archaen-Superior province, including Ely greenstone , metamorphosed and highly folded volcanics once thought to be
4440-713: The isostatic rebound of the land after recession of the last ice sheet. In the western part of the region in the Red River Valley, fine-grained glacial lake deposits and decayed organic materials up to 50 meters in depth form rich, well-textured, and moisture-retentive, yet well-drained soils ( mollisols ), which are ideal for agriculture. To the north and east, much of the land is poorly drained peat , often organized in rare and distinctive patterns known as patterned peatland . At marginally higher elevations within these wetlands are areas of black spruce, tamarack, and other water-tolerant species. Southwestern Minnesota
4560-421: The rock , minerals , and soils of the U.S. state of Minnesota , including their formation, development, distribution, and condition. The state's geologic history can be divided into three periods. The first period was a lengthy period of geologic instability from the origin of the planet until roughly 1,100 million years ago. During this time, the state's Precambrian bedrock was formed by volcanism and
4680-562: The voiced pharyngeal fricative , ⟨ ʕ ⟩, were inspired by other writing systems (in this case, the Arabic letter ⟨ ﻉ ⟩, ʿayn , via the reversed apostrophe). Some letter forms derive from existing letters: The International Phonetic Alphabet is based on the Latin script , and uses as few non-Latin letters as possible. The Association created the IPA so that the sound values of most letters would correspond to "international usage" (approximately Classical Latin ). Hence,
4800-542: The 150,000 words and phrases in VT's lexical database ... for their vocal stamina, attention to the details of enunciation, and most of all, knowledge of IPA". The International Phonetic Association organizes the letters of the IPA into three categories: pulmonic consonants, non-pulmonic consonants, and vowels. Pulmonic consonant letters are arranged singly or in pairs of voiceless ( tenuis ) and voiced sounds, with these then grouped in columns from front (labial) sounds on
4920-513: The Archean and become common late in the Archean. Cyanobacteria were instrumental in creating free oxygen in the atmosphere. Further evidence for early life is found in 3.47 billion-year-old baryte , in the Warrawoona Group of Western Australia. This mineral shows sulfur fractionation of as much as 21.1%, which is evidence of sulfate-reducing bacteria that metabolize sulfur-32 more readily than sulfur-34. Evidence of life in
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5040-437: The Archean has been destroyed by subsequent activity. The Earth's atmosphere was also vastly different in composition from today's: the prebiotic atmosphere was a reducing atmosphere rich in methane and lacking free oxygen . The earliest known life , mostly represented by shallow-water microbial mats called stromatolites , started in the Archean and remained simple prokaryotes ( archaea and bacteria ) throughout
5160-518: The Archean without leaving any. Fossil steranes , indicative of eukaryotes, have been reported from Archean strata but were shown to derive from contamination with younger organic matter. No fossil evidence has been discovered for ultramicroscopic intracellular replicators such as viruses . Fossilized microbes from terrestrial microbial mats show that life was already established on land 3.22 billion years ago. International Phonetic Alphabet The International Phonetic Alphabet ( IPA )
5280-524: The Archean, the conditions necessary to sustain life could not have occurred until the Archean Eon. Life in the Archean was limited to simple single-celled organisms (lacking nuclei), called prokaryotes . In addition to the domain Bacteria , microfossils of the domain Archaea have also been identified. There are no known eukaryotic fossils from the earliest Archean, though they might have evolved during
5400-673: The Des Moines terminal lobe mentioned above), so there is no glacial drift to form subsoils , giving the region the name of the Driftless area . As the topsoils are shallower and poorer than those to the west, dairy farming rather than cash crops is the principal agricultural activity. Central Minnesota is composed of (1) the drainage basin of the St. Croix River (2) the basin of the Mississippi River above its confluence with
5520-733: The Greek alphabet, though their sound values may differ from Greek. For most Greek letters, subtly different glyph shapes have been devised for the IPA, specifically ⟨ ɑ ⟩, ⟨ ꞵ ⟩, ⟨ ɣ ⟩, ⟨ ɛ ⟩, ⟨ ɸ ⟩, ⟨ ꭓ ⟩ and ⟨ ʋ ⟩, which are encoded in Unicode separately from their parent Greek letters. One, however – ⟨ θ ⟩ – has only its Greek form, while for ⟨ ꞵ ~ β ⟩ and ⟨ ꭓ ~ χ ⟩, both Greek and Latin forms are in common use. The tone letters are not derived from an alphabet, but from
5640-467: The IPA Handbook , the letters ⟨ c ⟩ and ⟨ ɟ ⟩ are used for /t͡ʃ/ and /d͡ʒ/ . Among the symbols of the IPA, 107 letters represent consonants and vowels , 31 diacritics are used to modify these, and 17 additional signs indicate suprasegmental qualities such as length , tone , stress , and intonation . These are organized into a chart; the chart displayed here
5760-579: The IPA have consisted largely of renaming symbols and categories and in modifying typefaces . Extensions to the International Phonetic Alphabet for speech pathology (extIPA) were created in 1990 and were officially adopted by the International Clinical Phonetics and Linguistics Association in 1994. They were substantially revised in 2015. The general principle of the IPA is to provide one letter for each distinctive sound ( speech segment ). This means that: The alphabet
5880-412: The IPA is used for broad phonetic or for phonemic transcription, the letter–sound correspondence can be rather loose. The IPA has recommended that more 'familiar' letters be used when that would not cause ambiguity. For example, ⟨ e ⟩ and ⟨ o ⟩ for [ɛ] and [ɔ] , ⟨ t ⟩ for [t̪] or [ʈ] , ⟨ f ⟩ for [ɸ] , etc. Indeed, in the illustration of Hindi in
6000-682: The IPA only for sounds not found in Czech . IPA letters have been incorporated into the alphabets of various languages, notably via the Africa Alphabet in many sub-Saharan languages such as Hausa , Fula , Akan , Gbe languages , Manding languages , Lingala , etc. Capital case variants have been created for use in these languages. For example, Kabiyè of northern Togo has Ɖ ɖ , Ŋ ŋ , Ɣ ɣ , Ɔ ɔ , Ɛ ɛ , Ʋ ʋ . These, and others, are supported by Unicode , but appear in Latin ranges other than
6120-537: The IPA remained nearly static until the Kiel Convention in 1989, which substantially revamped the alphabet. A smaller revision took place in 1993 with the resurrection of letters for mid central vowels and the retirement of letters for voiceless implosives . The alphabet was last revised in May 2005 with the addition of a letter for a labiodental flap . Apart from the addition and removal of symbols, changes to
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#17327647703726240-532: The IPA.) Of more than 160 IPA symbols, relatively few will be used to transcribe speech in any one language, with various levels of precision. A precise phonetic transcription, in which sounds are specified in detail, is known as a narrow transcription . A coarser transcription with less detail is called a broad transcription. Both are relative terms, and both are generally enclosed in square brackets. Broad phonetic transcriptions may restrict themselves to easily heard details, or only to details that are relevant to
6360-499: The International Phonetic Association. As of the most recent change in 2005, there are 107 segmental letters, an indefinitely large number of suprasegmental letters, 44 diacritics (not counting composites), and four extra-lexical prosodic marks in the IPA. These are illustrated in the current IPA chart , posted below in this article and on the International Phonetic Association's website. In 1886,
6480-717: The Iowa border between Mankato and New Ulm to the latitude of the Twin Cities , then encompassing the latter metropolis with a broad arc east to the St. Croix River . This moraine runs south from the Twin Cities in the general area of Minnesota State Highway 13 and Interstate 35 . Sansome attaches this moraine to her description of West-Central Minnesota, given its similarity in glacial features to that region. Under Sansome's classification (followed here), Southeastern Minnesota
6600-468: The Late Hadean is more controversial. In 2015, biogenic carbon was detected in zircons dated to 4.1 billion years ago, but this evidence is preliminary and needs validation. Earth was very hostile to life before 4,300 to 4,200 Ma, and the conclusion is that before the Archean Eon, life as we know it would have been challenged by these environmental conditions. While life could have arisen before
6720-548: The Late Precambrian Keweenawan volcanics of the Midcontinent Rift, overlaid by thousands of meters of sedimentary rocks. At the surface, the entire region is "Moraine terrain", with the glacial landforms of moraines , drumlins , eskers , kames , outwash plains and till plains , all relics from recent glaciation. In the multitude of glacier-formed depressions are wetlands and many of
6840-466: The Minnesota River basin. Most of the prairies are now farm fields. Due to the quaternary and bedrock geology of the region, as well as the reduced precipitation in the region, groundwater resources are neither plentiful nor widely distributed, unlike most other areas of the state. Given these constraints, this rural area hosts a vast network of water pipelines which transports groundwater from
6960-506: The Minnesota side of the coteau is a feature known as Buffalo Ridge , where wind speeds average 16 mph (26 km/h). This windy plateau has been developed for commercial wind power . Between the river and the plateau are flat prairies atop varying depths of glacial till. In the extreme southwest portion of the state, bedrock outcroppings of Sioux Quartzite are common, with less common interbedded outcrops of an associated metamorphosed mudstone named catlinite . Pipestone, Minnesota
7080-590: The Minnesota, (3) those parts of the Minnesota and Red River basins on the glacial uplands forming the divides of those two basins with that of the Mississippi, (4) the Owatonna Moraine atop a strip of land running from western Hennepin County south to the Iowa border, and (5) the upper valley of the Saint Louis River and the valley of its principal tributary the Cloquet River which once drained to
7200-521: The Mississippi at Prescott , Wisconsin. Upstream, the Mississippi is joined by the Minnesota River at historic Fort Snelling . When River Warren Falls receded past the confluence of the much smaller Upper Mississippi River , a new waterfall was created where that river entered the much-lower River Warren. The new falls receded upstream on the Mississippi, migrating eight miles (13 km) over 9600 years to where Louis Hennepin first saw it and named St. Anthony Falls in 1680. Due to its value as
7320-417: The Mississippi before they were captured by stream piracy and their waters were redirected through the lower Saint Louis River to Lake Superior. Glacial landforms are the common characteristics of this gerrymander -like region. The bedrock ranges in age from Archean granites to Upper Mesozoic Cretaceous sediments, and underlying the eastern part of the region (and the southerly extension to Iowa) are
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#17327647703727440-517: The Mississippi dropped 50 feet (15 m) over a limestone ledge; these waterfalls were used to drive the flour mills that were the foundation for the city's 19th century growth. Other bedrock tunnel valleys lie deep beneath till deposited by the glaciers which created them, but can be traced in many places by the Chain of Lakes in Minneapolis and lakes and dry valleys in St. Paul. North of
7560-912: The Northern Minnesota Peatlands of the Laurentian Mixed Forest, the Tallgrass Aspen Parklands, and the Red River Valley Section of the Prairie Parklands. Bedrock in this region is mainly Archean , with small areas of Lower Paleozoic and Upper Mesozoic sedimentary rocks along the western border. By late Wisconsinan times this bedrock had been covered by clayey glacial drift scoured and transported south from sedimentary rocks in Manitoba. The bottomland
7680-424: The above are provided by the IPA Handbook . The following are not, but may be seen in IPA transcription or in associated material (especially angle brackets): Also commonly seen are the braces of set theory , especially when enclosing the set of phonemes that constitute the morphophoneme, e.g. {t d} or {t|d} or {/t/, /d/} for a conflated /t/ and /d/ . Braces have
7800-589: The age of the planet. About 2,700 mya, the first volcanic rocks that would later underlie Minnesota began to rise up out of an ancient ocean, forming the Superior craton . This craton later assembled into the Canadian shield , which became part of the North American craton . Much of the underlying gneiss rock of today's state had already formed nearly a billion years earlier, but lay underneath
7920-617: The alphabet or the chart is to propose the change in the Journal of the IPA . (See, for example, December 2008 on an open central unrounded vowel and August 2011 on central approximants.) Reactions to the proposal may be published in the same or subsequent issues of the Journal (as in August 2009 on the open central vowel). A formal proposal is then put to the Council of the IPA – which
8040-441: The assembly and destruction of one and perhaps several supercontinents . Evidence from banded iron formations, chert beds, chemical sediments and pillow basalts demonstrates that liquid water was prevalent and deep oceanic basins already existed. Asteroid impacts were frequent in the early Archean. Evidence from spherule layers suggests that impacts continued into the later Archean, at an average rate of about one impactor with
8160-403: The conceptual counterparts of spoken sounds, are usually enclosed in slashes (/ /) and tend to use simpler letters with few diacritics. The choice of IPA letters may reflect theoretical claims of how speakers conceptualize sounds as phonemes or they may be merely a convenience for typesetting. Phonemic approximations between slashes do not have absolute sound values. For instance, in English, either
8280-535: The consonant is produced. The main chart includes only consonants with a single place of articulation. Notes Non-pulmonic consonants are sounds whose airflow is not dependent on the lungs. These include clicks (found in the Khoisan languages and some neighboring Bantu languages of Africa), implosives (found in languages such as Sindhi , Hausa , Swahili and Vietnamese ), and ejectives (found in many Amerindian and Caucasian languages ). Geology of Minnesota The geology of Minnesota comprises
8400-496: The consonant letters ⟨ b ⟩, ⟨ d ⟩, ⟨ f ⟩, ⟨ ɡ ⟩, ⟨ h ⟩, ⟨ k ⟩, ⟨ l ⟩, ⟨ m ⟩, ⟨ n ⟩, ⟨ p ⟩, ⟨ s ⟩, ⟨ t ⟩, ⟨ v ⟩, ⟨ w ⟩, and ⟨ z ⟩ have more or less their word-initial values in English ( g as in gill , h as in hill , though p t k are unaspirated as in spill, still, skill ); and
8520-552: The crystalline remnants of the surviving Archean crust. These include great melt sheets and voluminous plutonic masses of granite , diorite , layered intrusions , anorthosites and monzonites known as sanukitoids . Archean rocks are often heavily metamorphized deep-water sediments, such as graywackes , mudstones , volcanic sediments, and banded iron formations . Volcanic activity was considerably higher than today, with numerous lava eruptions, including unusual types such as komatiite . Carbonate rocks are rare, indicating that
8640-468: The deep oceans of the Archean probably covered the continents entirely. Only at the end of the Archean did the continents likely emerge from the ocean. The emergence of continents towards the end of the Archaean initiated continental weathering that left its mark on the oxygen isotope record by enriching seawater with isotopically light oxygen. Due to recycling and metamorphosis of the Archean crust, there
8760-473: The deposition of sedimentary rock and then modified by processes such as faulting , folding and erosion . In the second period, many layers of sedimentary rock were formed by deposition and lithification of successive layers of sediment from runoff and repeated incursions of the sea. In the third and most recent period starting about 1.8 million years ago, glaciation eroded previous rock formations and deposited deep layers of glacial till over most of
8880-786: The discussion at hand, and may differ little if at all from phonemic transcriptions, but they make no theoretical claim that all the distinctions transcribed are necessarily meaningful in the language. For example, the English word little may be transcribed broadly as [ˈlɪtəl] , approximately describing many pronunciations. A narrower transcription may focus on individual or dialectical details: [ˈɫɪɾɫ] in General American , [ˈlɪʔo] in Cockney , or [ˈɫɪːɫ] in Southern US English . Phonemic transcriptions, which express
9000-608: The end of words. the alternations /f/ – /v/ in plural formation in one class of nouns, as in knife /naɪf/ – knives /naɪvz/ , which can be represented morphophonemically as {naɪV } – {naɪV+z }. The morphophoneme {V } stands for the phoneme set {/f/, /v/ }. [ˈf\faɪnəlz ˈhɛld ɪn (.) ⸨knock on door⸩ bɑɹsə{ 𝑝 ˈloʊnə and ˈmədɹɪd 𝑝 }] — f-finals held in Barcelona and Madrid. IPA letters have cursive forms designed for use in manuscripts and when taking field notes, but
9120-456: The eon. The earliest photosynthetic processes, especially those by early cyanobacteria , appeared in the mid/late Archean and led to a permanent chemical change in the ocean and the atmosphere after the Archean. The word Archean is derived from the Greek word arkhē ( αρχή ), meaning 'beginning, origin'. The Pre-Cambrian had been believed to be without life (azoic); however, fossils were found in deposits that were judged to belong to
9240-592: The few localized areas with productive groundwater wells to much of the region's population. Southeastern Minnesota is separated from Southwestern Minnesota by the Owatonna Moraine , the eastern branch of the Bemis Moraine , a terminal moraine of the Des Moines lobe from the last Wisconsin glaciation . Ojakangas and Matsch extend the region west past the moraine to a line running north from
9360-403: The form of a chart. (See History of the IPA .) Not all aspects of the alphabet can be accommodated in a chart of the size published by the IPA. The alveolo-palatal and epiglottal consonants, for example, are not included in the consonant chart for reasons of space rather than of theory (two additional columns would be required, one between the retroflex and palatal columns and the other between
9480-412: The grapheme ⟨ g ⟩ of Latin script. Some examples of contrasting brackets in the literature: In some English accents, the phoneme /l/ , which is usually spelled as ⟨l⟩ or ⟨ll⟩ , is articulated as two distinct allophones: the clear [l] occurs before vowels and the consonant /j/ , whereas the dark [ɫ] / [lˠ] occurs before consonants, except /j/ , and at
9600-534: The ice sheet melted, and the Red River gave Lake Agassiz a northern outlet toward Hudson Bay . As the lake drained away its bed became peatlands and a fertile plain. Similarly, Glacial Lake Duluth , in the basin of Lake Superior, was dammed by a glacier; it drained down the ancient course of the Midcontinental Rift to the St. Croix River and the Mississippi. When the glaciers receded, the lake
9720-438: The implication of a preferred pronunciation that the IPA might convey. For example, the respelling systems in many American dictionaries (such as Merriam-Webster ) use ⟨y⟩ for IPA [ j] and ⟨sh⟩ for IPA [ ʃ ] , reflecting the usual spelling of those sounds in English. (In IPA, [y] represents the sound of the French ⟨u⟩ , as in tu , and [sh] represents
9840-454: The left to back (glottal) sounds on the right. In official publications by the IPA, two columns are omitted to save space, with the letters listed among "other symbols" even though theoretically they belong in the main chart. They are arranged in rows from full closure (occlusives: stops and nasals) at top, to brief closure (vibrants: trills and taps), to partial closure (fricatives), and finally minimal closure (approximants) at bottom, again with
9960-428: The left to back on the right, and from maximal closure at top to minimal closure at bottom. No vowel letters are omitted from the chart, though in the past some of the mid central vowels were listed among the "other symbols". A pulmonic consonant is a consonant made by obstructing the glottis (the space between the vocal folds) or oral cavity (the mouth) and either simultaneously or subsequently letting out air from
10080-408: The lungs. Pulmonic consonants make up the majority of consonants in the IPA, as well as in human language. All consonants in English fall into this category. The pulmonic consonant table, which includes most consonants, is arranged in rows that designate manner of articulation , meaning how the consonant is produced, and columns that designate place of articulation , meaning where in the vocal tract
10200-408: The natural ores pure enough to be fed directly into furnaces. The state's iron mines have produced over three and a half billion metric tons of ore. While high-grade ores have now been exhausted, lower-grade taconite continues to supply a large proportion of the nation's needs. Northwestern Minnesota is a vast plain in the bed of Glacial Lake Agassiz. This plain extends north and northwest from
10320-525: The neighboring island arcs and deposited in a forearc basin. Greenstone belts, which include both types of metamorphosed rock, represent sutures between the protocontinents. Plate tectonics likely started vigorously in the Hadean , but slowed down in the Archean. The slowing of plate tectonics was probably due to an increase in the viscosity of the mantle due to outgassing of its water. Plate tectonics likely produced large amounts of continental crust, but
10440-483: The oceans were more acidic, due to dissolved carbon dioxide , than during the Proterozoic. Greenstone belts are typical Archean formations, consisting of alternating units of metamorphosed mafic igneous and sedimentary rocks, including Archean felsic volcanic rocks . The metamorphosed igneous rocks were derived from volcanic island arcs , while the metamorphosed sediments represent deep-sea sediments eroded from
10560-602: The oldest exposed rock on earth; Proterozoic formations created about 1,900 mya that gave the area most of its mineral riches; and more recent intrusive gabbro and extrusive basalts and rhyolites of the Duluth Complex and North Shore Volcanic Group, created by magma and lava which upwelled and hardened about 1,100 mya during the Midcontinent Rift . The Precambrian bedrock formed by this activity has been eroded but remains at or close to
10680-715: The oldest rock formations exposed on the surface of the Earth are Archean. Archean rocks are found in Greenland , Siberia , the Canadian Shield , Montana , Wyoming (exposed parts of the Wyoming Craton ), Minnesota (Minnesota River Valley), the Baltic Shield , the Rhodope Massif , Scotland , India , Brazil , western Australia , and southern Africa . Granitic rocks predominate throughout
10800-449: The only remaining traces of the volcanism that ended over 1,100 mya. Landlocked within the continent, the state is far from the seas that once covered it, and the continental glacier has receded entirely from North America. Minnesota's landscape is a relatively flat peneplain ; its highest and lowest points are separated by only 518 metres (1,699 ft) of elevation. While the state no longer has true mountain ranges or oceans, there
10920-470: The parent soil for the state's farmlands, and glacial lakes are the backbone of Minnesota's tourist industry. These economic assets have in turn dictated the state's history and settlement patterns, and the trade and supply routes along the waterways, valleys and plains have become the state's transportation corridors. Minnesota contains some of the oldest rocks on Earth, granitic gneisses that formed some 3,600 mya (million years ago) — roughly 80%
11040-469: The pharyngeal and glottal columns), and the lateral flap would require an additional row for that single consonant, so they are listed instead under the catchall block of "other symbols". The indefinitely large number of tone letters would make a full accounting impractical even on a larger page, and only a few examples are shown, and even the tone diacritics are not complete; the reversed tone letters are not illustrated at all. The procedure for modifying
11160-420: The region continued to experience gradual subsidence and uplift. Five hundred fifty million years ago, the state was repeatedly inundated with water of a shallow sea that grew and receded through several cycles. The land mass of what is now North America ran along the equator, and Minnesota had a tropical climate. Small marine creatures such as trilobites , coral , and snails lived in the sea. The shells of
11280-509: The region north of the Mississippi but south of an east-west line from Saint Cloud to the St. Croix River on the Wisconsin border. It includes much of the Twin Cities metropolitan area. The region has the same types of glacial landforms as the remainder of Central Minnesota, but is distinguished by its bedrock valleys, both active and buried. The valleys now hold three of Minnesota's largest rivers, which join here. The St. Croix joins
11400-518: The regions as defined by Ojakangas and Matsch are more geographical in their approximations of areas of similar geology, while Sansome's divisions are more irregular in shape in order to include within a region all areas of similar geology, with particular emphasis on the effects of recent glaciation. As glaciation and its residue has largely dictated regional surface geology and topography, Sansome's divisions are often coextensive with ecological provinces, sections, and subsections. Northeastern Minnesota
11520-547: The remainder of the region, lakes provide recreation, forests are managed for pulpwood, and the underlying bedrock is mined for valuable ores deposited in Precambrian times. While copper and nickel ores have been mined, the principal metallic mineral is iron. Three of Minnesota's four iron ranges are in the region, including the Mesabi Range , which has supplied over 90% of the state's historic output, including most of
11640-687: The rest of the Archean continents have been recycled. By the Neoarchean , plate tectonic activity may have been similar to that of the modern Earth, although there was a significantly greater occurrence of slab detachment resulting from a hotter mantle, rheologically weaker plates, and increased tensile stresses on subducting plates due to their crustal material metamorphosing from basalt into eclogite as they sank. There are well-preserved sedimentary basins , and evidence of volcanic arcs , intracontinental rifts , continent-continent collisions and widespread globe-spanning orogenic events suggesting
11760-505: The rift filled with sediments, forming rock ranging in thickness from several hundred meters near Lake Superior to thousands of meters further south. While the crustal tectonic plates continued their slow drift over the surface of the planet, meeting and separating in the successive collision and sundering of continents, the North American craton remained stable. Although now free of folding and faulting caused by plate tectonics ,
11880-427: The same notation as for morphophonology, – exclamation marks, and pipes. For example, ⟨ cot ⟩ would be used for the orthography of the English word cot , as opposed to its pronunciation /ˈkɒt/ . Italics are usual when words are written as themselves (as with cot in the previous sentence) rather than to specifically note their orthography. However, italics are sometimes ambiguous, and italic markup
12000-454: The sea. Except for an area where islands appeared in what is now the northern part of the state, most of the region remained underwater. In Middle Precambrian time, about 2,000 mya, the land rose above the water. Heavy mineral deposits containing iron had collected on the shores of the receding sea to form the Mesabi , Cuyuna , Vermilion , and Gunflint iron ranges from the center of
12120-408: The sedimentary bedrock first encountered in many other regions, and glacial till is relatively sparse. While the effects of glacial erosion are clearly present and there are some areas of glacial till, older rocks and landforms remain unburied and exposed across much of the region. Contemporary Minnesota is much quieter geologically than in the past. Outcroppings of lava flows and magma intrusions are
12240-473: The sequence of consonants in gra ssh opper .) The IPA is also not universal among dictionaries in languages other than English. Monolingual dictionaries of languages with phonemic orthographies generally do not bother with indicating the pronunciation of most words, and tend to use respelling systems for words with unexpected pronunciations. Dictionaries produced in Israel use the IPA rarely and sometimes use
12360-467: The sound of the English digraph ⟨ch⟩ may be transcribed in IPA with a single letter: [c] , or with multiple letters plus diacritics: [t̠̺͡ʃʰ] , depending on how precise one wishes to be. Slashes are used to signal phonemic transcription ; therefore, /tʃ/ is more abstract than either [t̠̺͡ʃʰ] or [c] and might refer to either, depending on the context and language. Occasionally, letters or diacritics are added, removed, or modified by
12480-401: The state north into Northwestern Ontario , Canada. These regions also showed the first signs of life as algae grew in the shallow waters. Over 1,100 mya, a rift formed and lava emerged from cracks along the edges of the rift valley . This Midcontinent Rift System extended from the lower peninsula of Michigan north to the current Lake Superior , southwest through the lake to
12600-424: The state's "10,000 lakes", which make the area prime vacation territory. The glacial deposits are a source of aggregate, and underneath the glacial till are high-quality granites which are quarried for buildings and monuments. The subregion of East Central Minnesota is that part of Central Minnesota near the junction of three of the state's great rivers. Included are Dakota County , eastern Hennepin County , and
12720-470: The state's regions are covered with deep layers of glacial till. The driftless area of Southeastern Minnesota was untouched by the most recent glaciation. In the absence of glacial scouring and drift , this region presents a widespread and highly dissected aspect absent from other parts of the state. Northeastern Minnesota was subject to glaciation and its effects, but its hard Archaen and Proterozoic rocks were more resistant to glacial erosion than
12840-523: The state's topography and soils. Principal among these lakes was Lake Agassiz , a massive lake with a volume rivaling that of all the present Great Lakes combined. Dammed by the northern ice sheet, this lake's immense flow found an outlet in glacial River Warren , which drained south across the Traverse Gap through the valleys now occupied by the Minnesota and Mississippi Rivers . Eventually,
12960-508: The state, and created the beds and valleys of modern lakes and rivers. Minnesota's geologic resources have been the historical foundation of the state's economy . Precambrian bedrock has been mined for metallic minerals, including iron ore, on which the economy of Northeast Minnesota was built. Archaen granites and gneisses, and later limestones and sandstones, are quarried for structural stone and monuments. Glacial deposits are mined for aggregates, glacial till and lacustrine deposits formed
13080-524: The surface over much of the area. The entire area is the raw southern edge of the Canadian Shield . Topsoils are thin and poor and their parent soils derived from the rock beneath or nearby rather than from glacial till, which is sparse. Many of this region's lakes are located in depressions formed by the differential erosion of tilted layers of bedded rock of the Canadian Shield; the crevasses thereby formed have filled with water to create many of
13200-575: The thousands of lakes and swamps of the Superior National Forest . In post-glacial times Northeastern Minnesota was covered by forest broken only by these interconnected lakes and wetlands. Much of the area has been little changed by human activity, as there are substantial forest and wilderness preserves, most notably the Boundary Waters Canoe Area Wilderness and Voyageurs National Park . In
13320-849: The time, due to less land area and cloud cover. The processes that gave rise to life on Earth are not completely understood, but there is substantial evidence that life came into existence either near the end of the Hadean Eon or early in the Archean Eon. The earliest evidence for life on Earth is graphite of biogenic origin found in 3.7 billion–year-old metasedimentary rocks discovered in Western Greenland . The earliest identifiable fossils consist of stromatolites , which are microbial mats formed in shallow water by cyanobacteria . The earliest stromatolites are found in 3.48 billion-year-old sandstone discovered in Western Australia . Stromatolites are found throughout
13440-638: The tiny animals sank to the bottom, and are preserved in limestones , sandstones , and shales from this era. Later, creatures resembling crocodiles and sharks slid through the water, and fossil shark teeth have been found on the uplands of the Mesabi Range . During the Mesozoic and Cenozoic eras other land animals followed as the dinosaurs disappeared, but much of the physical evidence from this era has been scraped away or buried by recent glaciation . The rock units that remain in Minnesota from this time period are of Cambrian and Ordovician age, from
13560-457: The vowel letters ⟨ a ⟩, ⟨ e ⟩, ⟨ i ⟩, ⟨ o ⟩, ⟨ u ⟩ correspond to the (long) sound values of Latin: [i] is like the vowel in mach i ne , [u] is as in r u le , etc. Other Latin letters, particularly ⟨ j ⟩, ⟨ r ⟩ and ⟨ y ⟩, differ from English, but have their IPA values in Latin or other European languages. This basic Latin inventory
13680-463: The vowel of pick or the vowel of peak may be transcribed as /i/ , so that pick , peak would be transcribed as /ˈpik, ˈpiːk/ or as /ˈpɪk, ˈpik/ ; and neither is identical to the vowel of the French pique , which would also be transcribed /pik/ . By contrast, a narrow phonetic transcription of pick , peak , pique could be: [pʰɪk] , [pʰiːk] , [pikʲ] . IPA is popular for transcription by linguists. Some American linguists, however, use
13800-648: Was able to drain through the Great Lakes to the Saint Lawrence River . Giant animals roamed the area. Beavers were the size of bears , and mammoths were 14 feet (4.3 m) high at the shoulder and weighed 10 tons . Even buffalo were much larger than today. The glaciers continued to retreat and the climate became warmer over the next few millennia; the giant creatures died out about 9,000 years ago. This glaciation has drastically remodeled most of Minnesota, and all but two of
13920-612: Was based on the Romic alphabet , an English spelling reform created by Henry Sweet that in turn was based on the Palaeotype alphabet of Alexander John Ellis , but to make it usable for other languages the values of the symbols were allowed to vary from language to language. For example, the sound [ ʃ ] (the sh in shoe ) was originally represented with the letter ⟨c⟩ for English but with ⟨x⟩ for French and German; with German, ⟨c⟩
14040-558: Was enriched in heavier oxygen isotopes relative to the modern ocean, though δ18O values decreased to levels comparable to those of modern oceans over the course of the later part of the eon as a result of increased continental weathering. Astronomers think that the Sun had about 75–80 percent of its present luminosity, yet temperatures on Earth appear to have been near modern levels only 500 million years after Earth's formation (the faint young Sun paradox ). The presence of liquid water
14160-446: Was extended by adding small-capital and cursive forms, diacritics and rotation. The sound values of these letters are related to those of the original letters, and their derivation may be iconic. For example, letters with a rightward-facing hook at the bottom represent retroflex equivalents of the source letters, and small capital letters usually represent uvular equivalents of their source letters. There are also several letters from
14280-410: Was still twice the current level at the transition from the Archean to the Proterozoic (2,500 Ma ). The extra heat was partly remnant heat from planetary accretion , from the formation of the metallic core , and partly arose from the decay of radioactive elements. As a result, the Earth's mantle was significantly hotter than today. Although a few mineral grains have survived from the Hadean ,
14400-402: Was used for the [ x ] sound of Bach . With a growing number of transcribed languages this proved impractical, and in 1888 the values of the letters were made uniform across languages. This would provide the base for all future revisions. Since its creation, the IPA has undergone a number of revisions. After relatively frequent revisions and expansions from the 1890s to the 1940s,
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