:: wikimiki.org ::

Drumlin

Drumlin

] A drumlin (Gaelic druim the crest of a hill) is an elongated whale-shaped hill formed by glacial action. Its long axis is parallel with the movement of the ice, with the blunter end facing into the glacial movement. Drumlins may be more than 150 ft (45 m) high and more than 1/2 miles (0.8 km) long, and are often in drumlin fields of similarly shaped, sized and oriented hills. Drumlins usually have layers indicating that the material was repeatedly added to a core, which may be of rock or glacial till. There are many theories as to the exact mode of origin and plenty of controversy among geologists interested in geomorphology. Some consider them a direct formation of the ice, while a theory proposed since the 1980s by John Shaw and others postulates creation by a catastrophic flooding release of highly pressurized water flowing underneath the glacial ice. Either way, they are thought to be a waveform (similar to ripples of sand at the bottom of a stream). It is also poorly understood why drumlins form in some glaciated areas and not in others. Drumlins are common in New York, the lower Connecticut River valley, Minnesota, Wisconsin, Southern Ontario, Poland, Ireland, and Patagonia. They are regarded as a creation of the last Wisconsonian Ice age. Clew Bay in Ireland is a good example of a 'drowned drumlin' landscape where the drumlins appear as islands in the sea, forming a 'basket of eggs' topography. Ireland] A similar formation, with a more resilient (generally composed of igneous or metamorphic rock) core, is a Crag.

External links

- [http://www.geography-site.co.uk/pages/physical/glaciers/drum.html Diagrams of an idealized drumlin]
- [http://www.sentex.net/~tcc/sgfcrit.html Douglas E. Cox, "Drumlins and subglacial meltwater floods"]
- [http://www.sentex.net/~tcc/vortices1.html Douglas E. Cox, "The role of vortices in drumlin formation"] Introductions to the current dialogue. Category:Landforms Category:Glaciology

Glacier

:This article is about the geographical formation. For the professional wrestler, see Ray Lloyd A glacier is a large, long-lasting river of ice that is formed on land and moves in response to gravity. A glacier is formed by multi-year ice accretion in sloping terrain. Glacier ice is the largest reservoir of fresh water on Earth, and second only to the oceans as the largest reservoir of total water. Glaciers can be found on every continent except Australia. Geologic features associated with glaciers include end, lateral, ground and medial moraines that form from glacially transported rocks and debris; U-shaped valleys and corries (cirques) at their heads, and the glacier fringe, which is the area where the glacier has recently melted. cirques

Types of glaciers

cirques There are two main types of glaciers: alpine glaciers, which are found in mountain terrains, and continental glaciers, which are associated with ice ages and can cover large areas of continents. Most of the concepts in this article apply equally to alpine glaciers and continental glaciers. A temperate glacier is one where liquid water is present at least part of the year. Polar glaciers are always below the freezing point. The smallest alpine glaciers form in mountain valleys and are referred to as valley glaciers. Larger ice layers can cover an entire mountain, mountain chain or even a volcano; this type is known as an ice cap. Ice caps feed outlet glaciers, tongues of ice that extend into valleys below, far from the margins of those larger ice masses. Outlet glaciers are formed by the movement of ice from a polar ice cap, or an ice cap from mountainous regions, to the sea. The largest glaciers are continental ice sheets, enormous masses of ice that are not affected by the landscape and extend over the entire surface, except on the margins, where they are thinnest. Antarctica and Greenland are the only places where continental ice sheets currently exist. These regions contain vast quantities of fresh water. The volume of ice is so large that if the Greenland ice sheet melted, it would cause sea levels to rise some six meters all around the world. If the Antarctic ice sheet melted, sea levels would rise up to 65 meters. Plateau glaciers resemble ice sheets, but on a smaller scale. They cover some plateaus and high-altitude areas. This type of glacier appears in many places, especially in Iceland and some of the large islands in the Arctic Ocean, and throughout the northern Pacific Cordillera from southern British Columbia to western Alaska. Tidewater glaciers are glaciers that flow into the sea. As the ice reaches the sea pieces break off, or calve, forming icebergs. Most tidewater glaciers calve above sea level, which often results in a tremendous splash as the iceberg strikes the water. If the water is deep, glaciers can calve underwater, causing the iceberg to suddenly explode up out of the water. The Hubbard Glacier is the longest tidewater glacier in Alaska and has a calving face over ten kilometers long. Yakutat Bay and Glacier Bay are both popular with cruise ship passengers because of the huge glaciers descending to them. Piedmont glaciers occupy broad lowlands at the base of steep mountains, and form when one or more alpine glaciers surge from the confining walls of mountain valleys. The size of piedmont glaciers varies greatly: among the largest is the Malaspina Glacier, which extends along the length of the southern coast of Alaska. It covers more than 5,000 km² of the coastal plain at the foot of the Saint Elias range. And it is only a part of the much bigger Kluane Icecap, which spans the Mount St. Elias and Chugach groups of mountain ranges all the way from the Malaspina Glacier to the Copper River and well into the southwestern Yukon, as well as southeast from the Malaspina towards the Iskut River in British Columbia. The highest alpine glacier in the world is the Siachen Glacier, which is also a zone of political conflict between India and Pakistan.

Formation of glaciers

Siachen Glacier The snow which forms glaciers is subject to repeated freezing and thawing, which changes it into a form of granular ice called névé. Under 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. Glacial ice contains minute air bubbles as a result, giving it a distinctive blue tint due to Rayleigh scattering. The lower layers of glacial ice flow and deform plastically under the pressure, allowing the glacier as a whole to move slowly like a viscous fluid. Glaciers do not need a slope to flow, being driven by the continuing accumulation of new snow at their source. The upper layers of glaciers are more brittle, and often form deep cracks known as crevasses as they flex. These crevasses make travel over glaciers dangerous. Glacial meltwaters flow throughout and underneath glaciers, carving channels in the ice similar to caves in rock and also helping to lubricate the glacier's movement. In the summer, the melted ice from the glacier alone may be enough to create a stream, and while the glacier may be a barren waste of dense ice, fertile land is often nearby.

Anatomy of a glacier

cave The upper part of a glacier that receives most of the snowfall is called the accumulation zone. As a rule of thumb, the accumulation zone accounts for 60-70% of the glacier's surface area. The depth of ice in the accumulation zone exerts a downward force sufficient to cause deep erosion of the rock in this area. After the glacier is gone, this often leaves a bowl or amphitheater-shaped depression called a cirque. On the opposite end of the glacier, at its foot or terminal, is the deposition or ablation zone, where more ice is lost through melting than gained from snowfall and sediment is deposited. The place where the glacier thins to nothing is called the ice front. The altitude where the two zones meet is called the equilibrium line. At this altitude, the amount of new snow gained by accumulation is equal to the amount of ice lost through ablation. The downward erosive forces of the accumulation zone and the tendency of the ablation zone to deposit sediment also cancel each other out. Erosive lateral forces are not canceled; therefore, glaciers turn v-shaped river-carved valleys into u-shaped glacial valleys. The "health" of a glacier is defined by the area of the accumulation zone compared to the ablation zone. Healthy glaciers have large accumulation zones. Several non-linear relationships define the relation between accumulation and ablation. The worldwide shrinking of 70% of glaciers [http://www.grida.no/climate/ipcc_tar/wg1/064.htm] is among the evidence for global warming. Approximately 30% of glaciers are advancing. Even in very cold climates, there may be unglaciated areas, which receive too little precipitation to form permanent ice. This was the case in most of Siberia, central and northern Alaska and all of Manchuria during glacial periods of the Quaternary, and occurs today in that part of the Andes between 19°S and 27°S above the hyperarid Atacama Desert where, although the mountains reach 6700 metres above sea level, the cold Humboldt Current competely suppresses precipitation. During ice ages, continental glaciers may be as much as 1500 meters thick. A more extreme instance of glacial growth may have occurred during the Snowball Earth period. In the past several centuries the Earth's glaciers have generally been retreating, often dramatically.

Glacial motion

Earth Ice behaves like an easily breaking solid until its thickness exceeds about 50 meters (160 ft). Below that depth the increased pressure causes ice to become plastic and flow. The glacial ice is made up of layers of molecules stacked on top of each other, with relatively weak bonds between the layers. When the stress exceeds the inter-layer binding strength, the layers start to slide past each other. Another type of movement is basal gliding. In this process, the whole glacier moves over the terrain on which it sits, lubricated by thawed ice. As the pressure increases toward the base of the glacier, the melting point of water decreases, and the ice melts. Friction between ice and rock and geothermal heat from the Earth's interior also contribute to thawing. The top 50 meters of the glacier are more rigid. In this section, known as the fracture zone, there are no layers which slide past each other; instead the ice mostly moves as a single unit. Ice in the fracture zone moves over the top of the lower section. When the glacier moves through irregular terrain, cracks form in the fracture zone. These cracks can be up to 50 meters deep, at which point they meet the plastic flow underneath that seals them.

Speed of glacial movement

The speed of glacial displacement is partly determined by friction. Friction makes the ice at the bottom of the glacier move slower than the upper portion. In alpine glaciers, friction is also generated at the valley's side walls, which slows the edges relative to the center. This has been confirmed by experiments in the 19th century, in which stakes were planted in a line across an alpine glacier, and as time passed, those in the center moved further. Mean speeds vary; some have speeds so slow that trees can establish themselves among the deposited scourings. In other cases they can move as fast as many meters per day, as is the case of Byrd Glacier, an overflowing glacier in Antarctica which moves 750-800 meters per year (some 2 meters (6 ft) per day), according to studies using satellites. Many glaciers have periods of very rapid advancement called surges.[http://www.geog.leeds.ac.uk/research/glaciology/maths.htm] These glaciers exhibit normal movement until suddenly they accelerate, then return to their previous state. During these surges, the glacier may reach velocities up to 1000 times greater than normal.

Moraines

Glacial moraines are formed by the deposition of material from a glacier and are exposed after the glacier has retreated. These features usually appear as linear mounds of till, a poorly-sorted mixture of rock, gravel and boulders within a matrix of a fine powdery material. Terminal or end moraines are formed at the foot or terminal end of a glacier, lateral moraines are formed on the sides of the glacier, and medial moraines are formed down the center. Less obvious is the ground moraine, also called glacial drift, which often blankets the surface underneath much of the glacier downslope from the equilibrium line. Glacial meltwaters contain rock flour, an extremely fine powder ground from the underlying rock by the glacier's movement. Other features formed by glacial deposition include long snake-like ridges formed by streambeds under glaciers, known as eskers, and distinctive streamlined hills, known as drumlins. Stoss-and-lee erosional features are formed by glaciers and show the direction of their movement. Long linear rock scratches (that follow the glacier's direction of movement) are called glacial striations, and divots in the rock are called chatter marks. Both of these features are left on the surfaces of stationary rock that were once under a glacier and were formed when loose rocks and boulders in the ice were transported over the rock surface. Transport of fine-grained material within a glacier can smooth or polish the surface of rocks, leading to glacial polish. Glacial erratics are rounded boulders that were left by a melting glacier and are often seen perched precariously on exposed rock faces after glacial retreat. The most common name for glacial sediment is moraine. The term is of French origin, and it was coined by peasants to describe alluvial embankments and rims found near the margins of glaciers in the French Alps. Currently, the term is used more broadly, and is applied to a series of formations, all of which are composed of till.

Drumlins

till Drumlins are asymmetrical hills with aerodynamic profiles made mainly of till. Their heights vary from 15 to 50 meters and they can reach a kilometer in length. The tilted side of the hill looks toward the direction from which the ice advanced (stoss), while the longer slope follows the ice's direction of movement (lee). Drumlins are found in groups called drumlin fields or drumlin camps. An example of these fields is found east of Rochester, New York, and it is estimated that it contains about 10,000 drumlins. Although the process that forms drumlins is not fully understood, it can be inferred from their shape that they are products of the plastic deformation zone of ancient glaciers. It is believed that many drumlins were formed when glaciers advanced over and altered the deposits of earlier glaciers.

Glacial erosion

Rocks and sediments are added to glaciers through various processes. Glaciers erode the terrain principally through two methods: abrasion and plucking. plucking As the glacier flows over the bedrock's fractured surface, it softens and lifts blocks of rock that are brought into the ice. This process is known as plucking, and it is produced when subglacial water penetrates the fractures and the subsequent freezing expansion separates them from the bedrock. When the water expands, it acts as a lever that loosens the rock by lifting it. This way, sediments of all sizes become part of the glacier's load. Abrasion occurs when the ice and the load of rock fragments slide over the bedrock and function as sandpaper that smoothens and polishes the surface situated below. This pulverized rock is called rock flour. This flour is formed by rock grains of a size between 0.002 and 0.00625 mm. Sometimes the amount of rock flour produced is so high that currents of meltwaters acquire a grayish color. Another of the visible characteristics of glacial erosion are glacial striations. These are produced when the bottom's ice contains large chunks of rock that mark trenches in the bedrock. By mapping the direction of the flutes the direction of the glacier's movement can be determined. The velocity of a glacier's erosion is variable. The differential erosion undertaken by the ice is controlled by four important factors:
- Velocity of glacial movement
- Thickness of the ice
- Shape, abundance and hardness of rock fragments contained in the ice at the bottom of the glacier
- Relative ease of erosion of the surface under the glacier. Material that becomes incorporated in a glacier are typically carried as far as the zone of ablation before being deposited. Glacial deposits are of two distinct types:
- Glacial till: material directly deposited from glacial ice. Till includes a mixture of undifferentiated material ranging from clay size to boulders, the usual composition of a moraine.
- Fluvial and outwash: sediments deposited by water. These deposits are stratified through various processes, such as boulders being separated from finer particles. The larger pieces of rock which are encrusted in till or deposited on the surface are called glacial erratics. They may range in size from pebbles to boulders, but as they may be moved great distances they may be of drastically different type than the material upon which they are found. Patterns of glacial erratics provide clues of past glacial motions.

Glacial valleys

glacial erratics glacial erratics. Glacial lakes have been rapidly forming on the surface of the debris-covered glaciers in this region during the last few decades.]] Before glaciation, mountain valleys have a characteristic "V" shape, produced by downward erosion by water. However, during glaciation, these valleys widen and deepen, which creates a "U"-shaped glacial valley. Besides the deepening and widening of the valley, the glacier also smoothes the valley due to erosion. This way, it eliminates the spurs of earth that extend across the valley. Because of this interaction, triangular cliffs called truncated spurs are formed. Many glaciers deepen their valleys more than their smaller tributaries. Therefore, when the glaciers stop receding, the valleys of the tributary glaciers remain above the main glacier's depression, and these are called hanging valleys. In parts of the soil that were affected by abrasion and plucking, the depressions left can be filled by paternoster lakes, from the Latin for "Our Father", referring to a station of the rosary. At the head of a glacier is the corrie, which has a bowl shape with escarped walls on three sides, but open on the side that descends into the valley. In the corrie, an accumulation of ice is formed. These begin as irregularities on the side of the mountain, which are later augmented in size by the coining of the ice. After the glacier melts, these corries are usually occupied by small mountain lakes called tarns. There may be two glaciers separated by a diving ridge. This, located between the corries, is eroded to create an arête. This structure may result in a mountain pass. Glaciers are also responsible for the creation of fjords (deep coves or inlets) and escarpments that are found at high latitudes. With depths that can exceed 1,000 metres caused by the postglacial elevation of sea level and therefore, as it changed the glaciers changed their level of erosion. sea level

Arêtes and horns

An arête is a narrow crest with a sharp edge. Pointed pyramidal peaks are called horns. Both features may have the same process behind their formation: the enlargement of cirques from glacial plucking and the action of the ice. Horns are formed by cirques that encircle a single mountain. Arêtes emerge in a similar manner; the only difference is that the cirques are not located in a circle, but rather on opposite sides along a divide. Arêtes can also be produced by the collision of two parallel glaciers. In this case, the glacial tongues cut the divides down to size through erosion, and polish the adjacent valleys.

Sheepback rock

Some rock formations in the path of a glacier are sculpted into small hills with a shape known as roche moutonnée or sheepback. An elongated, rounded, asymmetrical, bedrock knob produced can be produced by glacier erosion. It has a gentle slope on its up-glacier side and a steep to vertical face on the down-glacier side. The glacier abrades the smooth slope that it flows along, while rock is torn loose from the downstream side and carried away in ice. Rock on this side is fractured by combinations of forces due to water, ice in rock cracks, and structural stresses.

Alluvial stratification

The water that rises from the zone of ablation moves away from the glacier and carries with it fine eroded sediments. As the speed of the water decreases, so does its capacity to carry objects in suspension. The water then gradually deposits the sediment as it runs, creating an alluvial plain. When this phenomenon occurs in a valley, it is called a valley train. alluvial plain Alluvial plains and valley trains are usually accompanied by basins known as kettles. Glacial depressions are also produced in till deposits. These depressions are formed when large ice blocks are stuck in the glacial alluvium and after melting, they leave holes in the sediment. Generally, the diameter of these depressions does not exceed 2 km, except in Minnesota, where some depressions reach up to 50 km in diameter, with depths varying between 10 and 50 meters.

Deposits in contact with ice

When a glacier reduces in size to a critical point, its flow stops, and the ice becomes stationary. Meanwhile, meltwater flows over, within, and beneath the ice leave stratified alluvial deposits. Because of this, as the ice melts, it leaves stratified deposits in the form of columns, terraces and clusters. These types of deposits are known as deposits in contact with ice. When those deposits take the form of columns of tipped sides or mounds, which are called kames. Some kames form when meltwater deposits sediments through openings in the interior of the ice. In other cases, they are just the result of fans or deltas towards the exterior of the ice produced by meltwater. When the glacial ice occupies a valley it can form terraces or kame along the sides of the valley. A third type of deposit formed in contact with the ice is characterized by long, narrow sinuous crests composed fundamentally of sand and gravel deposite by streams of meltwater flowing within, beneath or on the glacier ice. After the ice has melted these linear ridges or eskers remain as landscape features. Some of these crests have heights exceeding 100 meters and their lengths surpass 100 km.

Loess deposits

Very fine glacial sediments or rock flour is often picked up by wind blowing over the bare surface and may be deposited great distances from the original fluvial deposition site. These eolian loess deposits may be very deep, even hundreds of meters, as in areas of China and the midwestern United States.

Isostatic rebound

loess This rise of a part of the crust is due to an isostatic adjustment. A large mass, such as a glacier, depresses the Earth's crust. After the glacier melts, the crust begins to rise to its original position. This is post-glacial rebound and is currently occurring in measurable amounts in Scandinavia and the Great Lakes region of the United States.

Ice ages

:Main article: Ice age.

Ice age divisions

A quadruple division of the Quaternary glacial period has been established for North America and Europe. These divisions are based principally on the study of glacial deposits. In North America, each of these four stages was named for the state in which the deposits of these stages were well exposed. In order of appearance, they are the following: Nebraskan, Kansan, Illinoisan, and Wisconsinan. This classification was refined thanks to the detailed study of the sediments of the ocean floor. Because the sediments of the ocean floor, in contrast to that of the Earth's surface, are less affected by stratigraphic discontinuities, they are useful to determine the climatic cycles of the planet. In this matter, geologists have come to identify over twenty divisions, each of them lasting approximately 100,000 years. All these cycles fall within the Quaternary glacial period. During its peak, the ice left its mark over almost 30% of Earth's surface, covering approximately 10 million km² in North America, 5 million km² in Europe and 4 million km² in Siberia. The glacial ice in the Northern hemisphere was double that found in the Southern hemisphere. This is because in the South Pole the ice cannot advance beyond the Antarctic landmass. It is now believed that the most recent glacial period began between two and three million years ago, in the Pleistocene era.

Causes of ice ages

Little is known about the causes of glaciations. Generalized glaciations have been rare in the history of Earth. However, the Ice Age of the Pleistocene was not the only glaciative event, since tillite deposits have been identified. Tillite is a sedimentary rock formed when glacial till is lithified. These deposits found in strata of differing age present similar characteristics as fragments of fluted rock, and some are superposed over bedrock surfaces of channeled and polished rock or associated with sandstone and conglomerates that have features of alluvial plain deposits. Two Precambrian glacial episodes have been identified, the first approximately 2 billion years ago, and the second (Snowball Earth) about 600 million years. Also, a well documented record of glaciation exists in rocks of the late Paleozoic (of 250 million years of age). Although there are several scientific hypotheses about the determining factors of glaciations, the two most important ideas are plate tectonics and variations in Earth's orbit (Milankovitch cycles).

Plate tectonics

Because glaciers can form only on dry land, plate tectonics suggest that the evidence of previous glaciations is currently present in tropical latitudes due to the drift of tectonic plates from tropical latitudes to circumpolar regions. Evidence of glacial structures in South America, Africa, Australia, and India support this idea, because it is known that they experienced a glacial period near the end of the Paleozoic Era, some 250 million years ago. The idea that the evidence of middle-latitude glaciations is closely related to the displacement of tectonic plates was confirmed by the absence of glacial traces in the same period for the higher latitudes of North America and Eurasia, which indicates that their locations were very different than today. Climatic changes are also related to the positions of the continents, which has made them vary in conjunction with the displacement of plates. That also affected ocean current patterns, which caused changes in heat transmission and humidity. Since continents drift very slowly (about 2 cm per year), similar changes occur in periods of millions of years. A study of marine sediment that contained climatically sensitive microorganisms until about half a million years ago were compared with studies of the geometry of Earth's orbit, and the result was clear: climatic changes are closely related to periods of obliquity, precession, and eccentricity of the Earth's orbit. In general it can be affirmed that plate tectonics is only applicable to very long periods of time, while Milankovitch's proposal, backed up by the work of others, adjusts to the periodic alterations of glacial periods of the Pleistocene. These proposals are subject to uncertainty and there may be other factors involved.

References

- This article draws heavily on the corresponding article in the Spanish-language Wikipedia, which was accessed in the version of July 24, 2005.
- Michael Hambrey and Jürg Alean, Glaciers, 2nd ed. (Cambridge University Press, 2004, ISBN 0-521-82808-2) An excellent less-technical treatment of all aspects, with superb photographs and firsthand accounts of glaciologists' experiences. All images of this book can be found online (see Weblinks: Glaciers-online)
- Douglas I. Benn and David J. A. Evans, Glaciers and Glaciation (Arnold, 1999)
- M. R. Bennett and N. F. Glasser, Glacial Geology: Ice Sheets and Landforms (John Wiley & Sons, 1996)
- Michael Hambrey, Glacial Environments (University of British Columbia Press, UCL Press, 1994) An undergraduate-level textbook.
- Robert Walley, Introduction to Physical Geography (Wm. C. Brown Publishers, 1992) A textbook devoted to explaining the geography of our planet.
- W. S. B. Paterson, Physics of Glaciers, 3rd ed. (Pergamon Press, 1994) A comprehensive reference on the physical principles underlying formation and behavior.

External links

- [http://www.glaciers-online.net/ Swisseduc - Glaciers online]
- [http://www.nsidc.org/glaciers/ National Snow and Ice Data Center - Glaciers]
- [http://www.glaciers.er.usgs.gov/ USGS Glacier Studies Project]
- [http://vulcan.wr.usgs.gov/Glossary/Glaciers/description_glaciers_hazards.html Glaciers and Glacial Hazards - USGS]
- [http://www.sciencedaily.com/releases/2003/08/030814071654.htm 2003-08-15 Scientists Rewrite Laws Of Glacial Erosion]
- [http://www.nps.gov/kefj#Kenai Fjords National Park, Alaska]
- [http://www.pbs.org/wgbh/nova/sciencenow/3210/03.html NOVA scienceNOW] - A 7 minute video of the NOVA broadcast that aired on PBS, July 26, 2005. Hosted by Robert Krulwich, the video is about the world's fastest glacier and why it is moving too fast. Category:Glaciology Category:Bodies of ice Category:Glaciers ja:氷河

Drumlin field

] A drumlin field is a cluster of dozens to hundreds of similarly shaped, sized and oriented drumlins, also called a drumlin swarm. Drumlins are one type of landform that indicate continental ice sheet glaciation. The total depth of glacial deposits may be hundreds of feet deep.

Lake Ontario Example

The shaded relief map depicts a large drumlin field that exists in New York between the south shore of Lake Ontario and Cayuga Lake, which is just south of Montezuma Marsh. The old Cayuga valley north of Montezuma Marsh is almost entirely buried under the drumlin field. Possibly the bay at Fair Haven is a remnant of the old valley. This drumlin field is unique, in that it was greatly modified after it formed. Apparently, as the glacier retreated, it blocked the Lake Ontario outlet through the present St. Lawrence River for a long period, holding the lake at a higher level. A clearly marked shoreline resulted as shown by the light blue line. Drumlins north of that line were islands in the old, larger lake. Near the shore, wave action eroded and entirely removed the drumlins. Farther north, where the water was deeper, the waves eroded the top from each drumlin leaving them with an unusual flat top, instead of the normal elongated dome shape. There is evidence that the glacier did not advance in a straight line, but rather in the fashion of a tongue or lobe of ice. In the lower right of this image, the orientation of the drumlins show that the ice was moving east of south. As one looks at drumlins farther west, in the Rochester, New York area, it is seen that the drumlins show a turn to the west of south, and as one approaches the Niagara River, the drumlins align almost westward. Category:Glaciology

Glacial till

This article is about glacial sediments, for other uses see till (disambiguation). till (disambiguation) Till is an unsorted glacial sediment. Glacial drift is a general term for the coarsely graded and extremely heterogeneous sediments of glacial origin. Glacial till is that part of glacial drift which was deposited directly by the glacier. It may vary from clays to mixtures of clay, sand, gravel and boulders. A particularly sticky form of clay till is called gumbo. Clay in till may form balls called till balls. If a till ball rolls around in a stream and picks up rocks from the bed of the stream and becomes covered with them it may become an armored till ball. Till is deposited at the terminal moraine and along the lateral moraines of a glacier. As a glacier melts, especially a continental glacier large amounts of till are deposited by the rivers flowing from the glacier and in any proglacial lakes which may form. Till may contain alluvial deposits of gems or other valuable ore minerals picked up by the glacier during its advance, for example the diamonds found in Wisconsin, Indiana, and Canada. Prospectors use trace minerals in tills as clues to follow the glacier upstream to find kimberlite diamond deposits and other types of ore deposits.

Tillite

In cases where till has been indurated or lithified by subsequent burial into solid rock, it is known as the sedimentary rock tillite. Matching beds of ancient tillites on opposite sides of the south Atlantic Ocean provided early evidence for continental drift. The same tillites also provided the key evidence for the Precambrian Snowball Earth glaciation event.

Types of till

There are various types of classifying tills:
- primary deposits – these were laid down directly by glacier action
- secondary deposits – these have undergone reworking (e.g. fluvial transport, erosion, etc) Traditionally (e.g. Dreimanis, 1988), a further set of divisions has been made to primary deposits, based upon the method of deposition.
- Lodgement tills – sediment which has been deposited by plastering of glacial debris from a sliding glacier bed.
- Deformation tills – Sediment which has been disaggregated and (usually) homogenised by shearing in the sub glacial deformed layer.
- Melt out tills – Released by melting of stagnant or slowly moving debris-rich glacier ice and deposited without subsequent transport or deformation. Split up into sub glacial melt out till (melting of debris rich ice at the bottom of the glacier) and supraglacial melt-out till (melting of ice on the glacier surface).
- Sublimation till – similar to melt out till, except the ice is lost through sublimation rather than melt. Often only occurs in extremely cold and arid conditions, mainly in Antarctica. Some (e.g. Van der Meer et al. 2003) have suggested that these till classifications are outdated and should instead be replaced with only one classification, that of deformation till. The reasons behind this are largely down to the difficulties in accurately classifying different tills, which are often classified based on inferences of the physical setting of the till rather than till fabric or particle size analysis data. Category:Glaciology Category:Sedimentary rocks Category:Sediments

Theory

Theory has a number of distinct meanings in different fields of knowledge, depending on the context and their methodologies.

Etymology

The word ‘theory’ derives from the Greek ‘theorein’, which means ‘to look at’. According to some sources, it was used frequently in terms of ‘looking at’ a theatre stage, which may explain why sometimes the word ‘theory’ is used as something provisional or not completely resembling real. The term ‘theoria’ (a noun) was already used by the scholars of ancient Greeks.

Science

In scientific usage, a theory does not mean an unsubstantiated guess or hunch, as it does in other contexts. Neither is a scientific theory a fact. Scientific theories are never proven to be true, but can be disproven. All scientific understanding takes the form of hypotheses, theories, or laws. Theories are typically ways of explaining why things happen, often, but not always after the fact that they happen is no longer in scientific dispute. In referring to the "theory of global warming" for example, the worldwide temperatures have been measured and seem to be increasing. The "theory of global warming" refers instead to scientific work that attempts to explain how and why this could be happening. In various sciences, a theory is a logically self-consistent model or framework for describing the behavior of a certain natural or social phenomenon, thus either originating from or supported by experimental evidence (see scientific method). In this sense, a theory is a systematic and formalized expression of all previous observations made that is predictive, logical, testable, and has never been falsified. In physics, the term theory is generally used for a mathematical framework derived from a small set of basic principles, capable of producing experimental predictions for a given category of physical systems. A good example is electromagnetic theory, which encompasses the results that can be derived from Maxwell's equations. This theory is usually taken to be synonymous with classical electromagnetism. The term theoretical is used in science to describe a result that is predicted by theory but has not yet been observed. For example, until recently, black holes were considered theoretical. It is not uncommon in the history of physics for theory to produce predictions that are later confirmed by experiment; failed predictions, however, also occur, and sometimes work to falsify a theory. Conversely, at any time in the study of physics there can also be confirmed experimental results that are not yet explained by theory. For a given body of theory to be considered part of established scientific knowledge, it is usually necessary for it to characterize a critical experiment, namely an experimental result not predicted by any existing established theory. Unfortunately, usage of the term theory is muddled by scientists in such examples as string theory and various theories of everything, which are more correctly characterized at present as a bundle of competing hypotheses or a protoscience. A hypothesis, however, is still vastly more reliable than a conjecture, which is at best an untested guess consistent with selected data and often simply a belief based on non-repeatable experiments, anecdotes, popular opinion, "wisdom of the ancients," commercial motivation, or mysticism. Even worse, theory has almost the opposite meaning in common use than its definition in the sciences, and this change can be seen in modern dictionaries which now list theory as a "guess or hunch" in preference to the former scientific definition that used to be the dominant one. In everyday language, a theory is (Morrison, 2005, p. 39): :...a hunch that a detective comes up with in a murder mystery. It is one of several competing ideas, none of them proved. Fringe theories and conspiracy theories are crazy ideas that are out of the mainstream. New medicines or changes in the tax laws may be good in theory but don't work in practice. Among some scientists, theorists are thought to lack solid grounding in the facts... Even scientists tend to use the now common definition in everyday speech and writing, being more careful in published material. Yet a California Academy of Sciences exhibit on fossils included this line: "Scientists have a number of theories about why ammonites develop spines on their shells" (emphasis added; from Morrison, 2005).

Models

Humans construct theories in order to explain, predict and master phenomena (e.g. inanimate things, events, or the behaviour of animals). In many instances, this is seen to be the construction of models of reality. A theory makes generalizations about observations and consists of an interrelated, coherent set of ideas and models. According to Stephen Hawking in A Brief History of Time, "a theory is a good theory if it satisfies two requirements: It must accurately describe a large class of observations on the basis of a model that contains only a few arbitrary elements, and it must make definite predictions about the results of future observations." He goes on to state, "any physical theory is always provisional, in the sense that it is only a hypothesis; you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory. On the other hand, you can disprove a theory by finding even a single observation that disagrees with the predictions of the theory." This is borne out by what Isaac Asimov said in "Understanding Physics". He spoke of theories as "arguments" where one deduces a "scheme" or model. Arguments or theories always begin with Hawking's "arbitrary elements" which are here described as "assumptions". An assumption according to Asimov is "something accepted without proof, and it is incorrect to speak of an assumption as either true or false, since there is no way of proving it to be either. (If there were, it would no longer be an assumption.) It is better to consider assumptions as either useful or useless, depending on whether deductions made from them corresponded to reality. .. On the other hand, it seems obvious that assumptions are the weak points in any argument, as they have to be accepted on faith in a philosophy of science that prides itself on its rationalsim. Since we must start somewhere, we must have assumptions, but at least let us have as few assumptions as possible." (See Ockham's razor) An example of using assumptions to formulate a theory is when Albert Einstein put forth his Special Theory of Relativity. He took two phenomena that had been observed i.e. that the "addition of velocities" is valid (Galilean transformation) and that light did not appear to have an "addition of velocities" (Michelson-Morley experiment). He assumed that both of these were correct and formulated his theory based on these assumptions by simply altering the Galilean transformation to accommodate the lack of addition of velocities with regard to the speed of light. Therefore, the model created in his theory is based on the assumption that light maintains a constant velocity (or more precisely the speed of light is a constant). An example of how theories are models can be seen from theories on the planetary system. The Greeks formulated theories that were recorded by the astronomer Ptolemy. In Ptolemy's planetary model, the earth was at the center, the planets and the sun made circular orbits around the earth, and the stars were on a sphere outside of the orbits of the planet and the earth. Retrograde motion of the planets was explained by smaller circular orbits of individual planets. This could actually be built into a literal model and illustrated as a model. Mathematical calculations could be made for the prediction of where the planets would be to a great degree of accuracy, so that this model of the planetary system survived over 1500 years until the time of Copernicus. So one can see how a theory is a model of reality that explains certain scientific facts yet may not be a true picture of reality and another more accurate theory can later replace the previous model.

Types of theories

There are two uses of the word theory; a supposition which is not backed by observation is known as a conjecture, and if backed by observation it is a hypothesis. Most theory evolves from hypotheses, but the reverse is not true: many hypotheses turn out to be false and so do not evolve into theory. A theory is different from a theorem. The former is a model of physical events and cannot be proved from basic axioms. The latter is a statement of mathematical fact which logically follows from a set of axioms. A theory is also different from a physical law in that the former is a model of reality whereas the latter is a statement of what has been observed. Theories can become accepted if they are able to make correct predictions and avoid incorrect ones. Theories which are simpler, and more mathematically elegant, tend to be accepted over theories which are complex. Theories are more likely to be accepted if they connect a wide range of phenomena. The process of accepting theories, or of extending existing theory, is part of the scientific method.

Further explanation of a scientific theory

As noted above, in common usage a theory is defined as little more than a guess or a hypothesis. But in science and generally in academic usage, a theory is much more than that. A theory is an established paradigm that explains all or much of the data we have and offers valid predictions that can be tested. In science, a theory is not considered fact or infallible, because we can never assume we know all there is to know. Instead, theories remain standing until they are disproved, at which point they are thrown out altogether or modified to fit the additional data. Theories start out with empirical observations such as "sometimes water turns into ice." At some point, there is a need or curiosity to find out why this is, which leads to a theoretical/scientific phase. In scientific theories, this then leads to research, in combination with auxiliary and other hypotheses (see scientific method), which may then eventually lead to a theory. Some scientific theories (such as the theory of gravity) are so widely accepted that they are often seen as laws. This, however, rests on a mistaken assumption of what theories and laws are. Theories and laws are not rungs in a ladder of truth, but different sets of data. A law is a general statement based on observations. A canonical example of a disproved theory is the geocentric model of the universe proposed by Ptolemy. Evidence, in the form of Galileo's observation of the phases of Venus in 1610, was produced which was completely incompatible with the predictions set forth by the theory. This falsification, though, did not necessarily mean that only one alternative theory was necessarily the "correct" replacement — both the Copernican system and the Tychonian system predicted the phases of Venus.

Characteristics

In science, a body of descriptions of knowledge is usually only called a theory once it has a firm empirical basis, i.e., it # is consistent with pre-existing theory to the extent that the pre-existing theory was experimentally verified, though it will often show pre-existing theory to be wrong in an exact sense, # is supported by many strands of evidence rather than a single foundation, ensuring that it probably is a good approximation if not totally correct, # makes predictions that might someday be used to disprove the theory, # is tentative, correctable and dynamic, in allowing for changes to be made as new data is discovered, rather than asserting certainty, and # is the most parsimonious explanation, sparing in proposed entities or explanations, commonly referred to as passing Occam's Razor. This is true of such established theories as special and general relativity, quantum mechanics, plate tectonics, evolution, etc. Theories considered scientific meet at least most, but ideally all, of the above criteria. The fewer which are matched, the less scientific it is; those that meet only several or none at all, cannot be said to be scientific in any meaningful sense of the word. Karl Popper described the characteristics of a scientific theory as: 1. It is easy to obtain confirmations, or verifications, for nearly every theory — if we look for confirmations. 2. Confirmations should count only if they are the result of risky predictions; that is to say, if, unenlightened by the theory in question, we should have expected an event which was incompatible with the theory — an event which would have refuted the theory. 3. Every "good" scientific theory is a prohibition: it forbids certain things to happen. The more a theory forbids, the better it is. 4. A theory which is not refutable by any conceivable event is non-scientific. Irrefutability is not a virtue of a theory (as people often think) but a vice. 5. Every genuine test of a theory is an attempt to falsify it, or to refute it. Testability is falsifiability; but there are degrees of testability: some theories are more testable, more exposed to refutation, than others; they take, as it were, greater risks. 6. Confirming evidence should not count except when it is the result of a genuine test of the theory; and this means that it can be presented as a serious but unsuccessful attempt to falsify the theory. (I now speak in such cases of "corroborating evidence.") 7. Some genuinely testable theories, when found to be false, are still upheld by their admirers — for example by introducing ad hoc some auxiliary assumption, or by reinterpreting the theory ad hoc in such a way that it escapes refutation. Such a procedure is always possible, but it rescues the theory from refutation only at the price of destroying, or at least lowering, its scientific status. (I later described such a rescuing operation as a "conventionalist twist" or a "conventionalist stratagem.") One can sum up all this by saying that the criterion of the scientific status of a theory is its falsifiability, or refutability, or testability."--end quote

Mathematics

In mathematics, the word theory is used informally to refer to certain distinct bodies of knowledge about mathematics. This knowledge consists of axioms, definitions, theorems and computational techniques, all related in some way by tradition or practice. Examples include group theory, set theory, Lebesgue integration theory and field theory. The term "theory" also has a formal usage in mathematics, particularly in mathematical logic and model theory. A theory in this sense is a set of statements closed under certain rules of inference. A typical theory will present certain axioms and rules, corresponding to a useful or interesting abstraction, and then derive non-obvious theorems from those axioms. The resulting theorems often provide solutions to real-world problems which correspond to the original abstraction. Obvious examples include arithmetic (abstracting the concept of number), geometry (the concept of space), and probability (the concept of randomness). However, Gödel's incompleteness theorem shows that no consistent theory capable of defining the concept of natural numbers can derive all true statements about those numbers. This sets a fundamental limit to the applicability of any mathematical system.

Other fields

Theories exist not only in the so-called hard sciences; but in all fields of academic study, from philosophy to music to literature. In the humanities, theory is often used as an abbreviation for critical theory or literary theory, referring to continental philosophy's aesthetics or its attempts to understand the structure of society and to conceptualize alternatives. In philosophy, theoreticism refers to the overuse of theory.

List of famous theories

- Mathematics: Axiomatic set theory - Chaos theory - Graph theory - Number theory - Probability theory
- Statistics : Extreme value theory
- Physics: Theory of relativity - Special relativity - General relativity - Quantum field theory - Acoustic theory - Antenna theory
- Planetary science: Giant impact theory
- Biology: Evolution by natural selection - Cell theory
- Chemistry: Atomic theory - Kinetic theory of gases
- Geology: Continental drift - Plate tectonics
- Climatology: Global warming
- Humanities: Critical theory
- Sociology: Social Theory - Critical social theory - Value theory
- Philosophy: Speculative reason
- Literature: Literary theory
- Music: Music theory
- Computer science: Algorithmic information theory - Computation theory
- Games: Rational choice theory - Game theory
- Other: Obsolete scientific theories - Phlogiston theory

Reference

- Morrison, David. 2005. "Only a theory? Framing the evolution/creation issue". Skeptical Inquirer, 29 (6): 37-41.
- Karl Popper, Conjectures and Refutations, London: Routledge and Keagan Paul, 1963, pp. 33-39; from Theodore Schick, ed., Readings in the Philosophy of Science, Mountain View, CA: Mayfield Publishing Company, 2000, pp. 9-13. Theories Category:Scientific method Category:Mathematical terminology Category:Philosophy of science ja:理論

Geomorphology

Geomorphology is the study of landforms, including their origin and evolution, and the processes that shape them. The underlying question is: Why do landscapes look the way they do? The term is derived from the Greek geo, meaning Earth, and morph, meaning form. Geomorphologists seek to understand landform history and dynamics, and predict future changes through a combination of field observation, physical experiment, and numerical modeling. The discipline is practiced within geology, geography, archaeology and civil and environmental engineering. Early studies in geomorphology are the foundation for pedology, one of two main branches of soil science. Landforms evolve in response to a combination of natural and anthropogenic processes. The landscape is built up through tectonic uplift and volcanism. Denudation occurs by erosion and mass wasting, which produces sediment that is transported and deposited elsewhere within the landscape or off the coast. Landscapes are also lowered by subsidence, either due to tectonics or physical changes in underlying sedimentary deposits. These processes are each influenced differently by climate, ecology, and human activity. Particular applications of geomorphology include landslide prediction and mitigation, river control and restoration, coastal protection, and even assessing the presence of water on Mars.

History

Geomorphology was not originally differentiated from the rest of geography. The first geomorphic model was the geographical cycle or the cycle of erosion, developed by William Morris Davis between 1884 and 1899. The cycle was inspired by theories of evolution, and was depicted as a sequence by which a river would cut a valley more and more deeply, but then erosion of side valleys would eventually flatten out the terrain again, now at a lower elevation. The cycle could be started over by uplift of the terrain. The model is today considered too much of a simplification to be especially useful in practice. Walther Penck developed an alternative model in the 1920s, based on ratios of uplift and erosion, but it was also too weak to explain a variety of landforms.

Processes

1920s Modern geomorphology focuses on the quantitative analysis of interconnected processes, such as the contribution of solar energy, the rates of steps of the hydrologic cycle, and plate movement rates from geophysics to compute the age and expected fate of landforms. The use of more precise measurement technique has also enabled processes like erosion to be observed directly, rather than merely surmised from other evidence. Computer simulation is also valuable for testing that a particular model yields results with properties similar to real terrain. Primary surface processes responsible for most topographic features include wind, waves, weathering, mass wasting, ground water, surface water, glaciers, tectonism, and volcanism.

Fluvial Geomorphology

Rivers and streams are not only conduits of water, but also of sediment. The water, as it flows over the channel bed, is able to mobilise sediment and transport it downstream, either as bedload, suspended load or dissolved load. The rate of sediment transport depends on the avilability of sediment itself and on the river's discharge. As rivers flow across the landscape, they generally increase in size, merging with other rivers. The network of rivers thus formed is a drainage system and is often dendritic, but may adopt other patterns depending on the regional topography and underlying geology.

Glacial Geomorphology

Glaciers, while geographically restricted, are effective agents of landscape change. The gradual movement of ice down a valley causes abrasion and plucking of the underlying rock. Abrasion produces fine sediment, termed glacial flour. The debris transported by the glacier, when the glacier recedes, is termed a moraine. Glacial erosion is responsible for U-shaped valleys, as opposed to the V-shaped valleys of fluvial origin.

Weathering

Main article: Weathering. This results from chemical dissolution of rock and from the mechanical wearing of rock by plant roots, ice expansion, and the abrasive action of sediment. Weathering provides the source of the sediment transported by fluvial, glacial, aeolian, or biotic processes.

Taxonomy

Different geomorphological processes dominate at different spatial and temporal scales. To help categorize landscape scales some geomorphologists use the following taxonomy:
- 1st - Continent, ocean basin, climatic zone (~10,000,000 km²)
- 2nd - Shield, e.g. Baltic shield, or mountain range (~1,000,000 km²)
- 3rd - Isolated sea, Sahel (~100,000 km²)
- 4th - Massif, e.g. Massif Centralor Group of related landforms, e.g., Weald (~10,000 km²)
- 5th - River valley, Cotswolds (~1,000 km²)
- 6th - Individual mountain or volcano, small valleys (~100 km²)
- 7th - Hillslopes, stream channels, estuary (~10 km²)
- 8th - gully, barchannel (~1 km²)
- 9th - Meter-sized features Its use, however, is rare and may be misleading - the nature of landscape change may be better viewed as a continuum of coupled processes.

References

- M. J. Selby, Earth's Changing Surface (Oxford University Press, 1985) ISBN 0198232527
- Richard Chorley, Stanley Schumm, and David Sugden, Geomorphology (Methuen, 1984)

External link

- [http://www.abdn.ac.uk/~geo337/gg4514/davis.htm The Geographical Cycle, or the Cycle of Erosion (1899)] Category:Geology Category:Physical geography
-

Minnesota

Minnesota is the 32nd state of the United States, having joined the Union on May 11, 1858. Its name is from the Dakota people's name for the Minnesota River, mini sota, variously translated "smoky-white water" or "sky-tinted water." The state's name is abbreviated MN or Minn. Minnesota is the largest state by land area in the Midwestern United States and is in the sub-region known as the Upper Midwest. The most significant metropolitan area is known as the Twin Cities, which contains more than half the state's population. The Twin Cities refer to the state's most populous cities- Minneapolis and Saint Paul, along with multiple "rings" of suburbs. The state is a major food producer for the country, and has a number of natural resources that have been greatly exploited in the last two centuries. The USS Minnesota was named in honor of this state, as was the SS Gopher State. Other nicknames for the state include The Land of 10,000 Lakes and the North Star State.

History

Main article: History of Minnesota

History prior to joining the United States

Before European colonization, the area now known as Minnesota was inhabited by Native Americans, in particular the Ojibwe (Chippewa, Anishinaabe) and Dakota, although the Winnebago also had a presence in the southeastern part of the state. In this time, the economy originally consisted of hunter-gatherer activities, which changed over time as Europeans settled in the area and further exploited the state's natural resources. Before the arrival of Dakota and Ojibwe, Cheyenne and Gros Ventre also made their home in Minnesota. According to local tradition, the first European visitors were Swedish and Norwegian Vikings in the 14th century. The evidence for this is largely based on the controversial Kensington Runestone, which many historians consider to be an elaborate hoax. Some say that the earliest European settlement was in the area of the current city of Stillwater, on the St. Croix River, though many histories focus on the military settlement that took place farther west. Fort Snelling, located at the confluence of the Minnesota River and the Mississippi River, was one of the earliest U.S. military presences in the state. It is now a historic site.

Joining the United States

Much of the state was purchased from France as part of the Louisiana Purchase, although the exact definition of that land was not assessed for many years afterward. Parts were also considered to be in the Northwest Territory and Ruperts Land. Minnesota Territory was carved out of Iowa Territory on March 3, 1849, but it was not coextensive with the present state, since the area included what later became the territory of Dakota (which later still became the states of North Dakota and South Dakota). The eastern half of the territory of Minnesota became the country's 32nd state—after California—on May 11, 1858.

Culture

Stereotypical Minnesotan traits include Lutheranism, "Minnesota nice," "hot dish (a Minnesotan term for casserole)," lutefisk (a pungent preparation of fish from a Norwegian recipe that includes soaking in lye), very close family ties (and a strong sense of duty to their families, healthy and dysfunctional alike), a strong sense of community and shared culture with many other Minnesotans instead of just with one's town or city, Minnesota's rather unique form of Upper Midwest American English (including Scandinavian-sounding words like "uff-da"), and a distinctive type of upper Midwestern accent, though most Minnesotans deny having any regional accent. However, due to the increase of migrants from throughout the United States (many originating from the West Coast and the Chicago metropolitan area ) and the rise of immigration of Hmong, Vietnamese, Somalis and other East Africans, Liberians, Kenyans, Nigerians, Russians, Eastern Europeans and Latin Americans (mostly Mexicans), many cultures in the state are slowly blending together and slowing changing the culture of the state similar to what European immigrants to Minnesota had done in the mid 19th Century to early 20th Century. Native Americans have a moderate presence in Minnesota, and some tribes operate casinos which have been said to be among the most profitable in the country. The earliest European exploration and settlement was by the French, and settlement from Scandinavian countries along with Germany followed. The Métis people, a mixed French and Native American culture, were a presence in the early state and territorial days, but largely moved north into Canada. Minnesota is not strongly associated with any particular food, though in recent years dishes like wild rice sausage have come from the state and more will undoubtedly follow as Minnesotan chefs seek to define their home in the culinary world. Modern immigrants have come from all over the world in recent decades, with Hmong, Somali, Vietnamese, Indians, Middle Easterners, and the former Soviet bloc all being well-represented. Some Chinese and Japanese have had long presences in the state as well. Mexicans are a growing force, as they are across the U.S. Many modern immigrants are attracted by the state's historically strong commitments toward education and social services and many come sponsored and assisted by congregations committed to service and social justice. Outdoor activities are major parts of the lives of many Minnesotans, including hunting and fishing. Unique activities include ice fishing, which was popular with the early Scandinavian immigrants. Families frequently own or share cabins on central and northern tracts of land in forests and adjoining lakes, and weekend trips out to these properties are common. The 71 state parks which protect diverse landscapes in a state of nature are quite popular. A concern for environmentalism is shared by most state residents in one form or another, vegans and hunters alike. As with other northwoods states (such as Wisconsin and Michigan), residents like to joke that the mosquito is the state bird. The state bird is actually the common loon (Gavia immer, also called the Great northern diver), whose distinctive cry can often be heard by campers in the northern part of the state and can even on occasion be found as far south as Minneapolis. Minnesota is known for active yet quirky politics, with populism being a long-standing force among all of the political parties that call the state home. Minnesota politics include such oddities as a professional wrestler turned governor and a protestor turned crowd-surfing mayor. 77.3% of eligible Minnesotans voted in the 2004 U.S. presidential election, the highest of any U.S. state. Political conservatism is less strongly linked to church attendance in most of Minnesota than in other parts of the country, perhaps a reflection of the strong mainline Protestant and Roman Catholic following.

Law and government

As in the national government of the United States, power in Minnesota is divided into three main branches: Executive, Legislative, and Judicial. The executive branch is headed by the governor, currently Tim Pawlenty, a Republican, whose term began 6 January, 2003. The current lieutenant governor of Minnesota is Carol Molnau. Molnau also currently serves as the head of the Minnesota Department of Transportation. Both the governor and lieutenant governor have four-year terms. The governor has a cabinet consisting of the leaders of various government agencies in the state, called commissioners. The full list of governors, and the dates they took office, is available at List of Governors of Minnesota. The Minnesota Legislature is a bicameral body consisting of the Senate and the House of Representatives. The state has 67 districts, each covering about 60,000 people. Each district has one senator and two representatives (each district being divided into A and B subsections). Senators serve for four years, and representatives serve for two years. In the November 2004 election, the Republican Party retained control of the Minnesota House of Representatives by a single seat (68-66), having lost a total of 13 seats. The Minnesota Senate is controlled by the Minnesota Democratic-Farmer-Labor Party (DFL). After picking up one seat in a local special election on 16 November, 2005, the DFL controls the senate by six seats (36-30-1). There is one Independence Party state senator, former Republican Sheila Kiscaden (IP-Rochester) who caucuses with the DFL. As a result of its liberal and populist political culture throughout much of the latter half of the 20th century, Minnesota has voted for Democrats for president longer than any other state (excluding the District of Columbia), since 1976. Minnesota and the District of Columbia were the only electoral votes not won by incumbent Republican president Ronald Reagan, voting instead for former Vice President of the United States and former U.S. Senator Walter Mondale, a Minnesota native. In 2004, John Kerry narrowly won the state's 10 electoral votes by a margin of three percentage points with 51.1% of the vote. Republican strength is greatest in southern Minnesota and the suburbs of Minneapolis, especially in the area west of the city, and in developing outer suburban communities. Democrats hold tremendous strength in Minneapolis/St. Paul proper and in the Iron Range of northeastern Minnesota, including Duluth. The state also enjoys a strong and active third party movement. The Reform Party was able to elect former mayor of Brooklyn Park, and former wrestling superstar Jesse Ventura to the governorship in 1998, however Ventura left the Reform Party in 2000 when Pat Buchanan took control. Ventura maintained close ties to the Independence Party, but chose not to seek reelection. In 2002 the Independence Party ran former democratic congressman Tim Penny in an unsuccessful bid for the governorship. Penny earned over 20% of the vote. The states Green Party has elected several city councilmembers and other local office-holders in Duluth, Minneapolis and Winona, and has made strong runs for state legislature during the past two election cycles. In 2000, Green Party candidate Ralph Nader received just over 5% of the presidential votes cast, gaining Major Party Status for the Green Party of Minnesota. Minnesota's court system has three levels:
- Trial courts. The state is split into 10 judicial districts, with 257 judges. Most state cases start in the trial courts.
- Minnesota Court of Appeals. This body hears appeals on cases tried in the trial courts. There are 16 judges, who divide into three-judge panels to hear appeals in courts across the state.
- Minnesota Supreme Court. The seven justices on the Supreme Court hear appeals from the Court of Appeals, the Tax Court, and the Worker's Compensation Court. The court automatically reviews first-degree murder convictions, and settles disputes over legislative elections. The state has two special courts created by state law as executive-branch agencies:
- The Tax Court deals with non-criminal tax cases across the state. It has three judges appointed by the governor to six-year terms, following approval from the state Senate
- The Workers' Compensation Court of Appeals deals with cases involving worker injuries referred to it on appeal, or transferred from district court. It has five judges appointed by the governor to six-year terms, following approval from the state Senate Federal cases are heard in the federal district courts in Minneapolis, St. Paul, or Duluth. Minnesota is part of the Eighth Circuit Court of Appeals, which is based in St. Louis, Missouri. Appeals beyond this level go to the U.S. Supreme Court in Washington, D.C.. In addition to the standard city and county levels of government found in the United States, Minnesota also has other entities that provide governmental oversight and planning. Some actions in the Twin Cities metropolitan area are coordinated by the Metropolitan Council, and many lakes and rivers are overseen by watershed districts and soil and water conservation districts. See also: List of political parties in Minnesota External links: [http://www.house.leg.state.mn.us/cco/rules/mncon/preamble.htm Hyperlinked state constitution], [http://www.house.leg.state.mn.us/cco/rules/mncon/mncon.htm full text of state constitution]

Geography

List of political parties in Minnesota See: List of Minnesota counties Minnesota covers 79,610 square miles (2.25% of the United States). It is famous for its lakes, having in excess of 15,000, depending on the source of the count. Much of the state is flat, having been eroded during repeated glacial periods (most recently the Wisconsin Glacier). However, the extreme southeastern portion of the state is part of the Driftless Zone, which was not glaciated, and it is here that Lake Pepin and the rugged high bluffs of the Mississippi River are found. In addition, the Iron Range and other low mountains are found in the northeastern part of the state. The Minnesota portion of Lake Superior is the largest body of water in the state. Minnesota is home to many areas of park land, to the Boundary Waters Canoe Area Wilderness (BWCAW), as well as a number of state and county parks, most notably Itasca State Park, the official source of the Mississippi River. After its rivers and lakes, Minnesota's most prominent physical feature is the Iron Range. This is a range of low mountains that run across the northern part of the state. It is called the Iron Range because when discovered, it had some of the largest deposits of iron ore in the country. Although the high-grade iron ore was mostly mined out during World War II, taconite is still mined across the Iron Range. The state is bordered on the north by Canada (Manitoba and Ontario), on the east by Wisconsin and Lake Superior, on the south by Iowa, and on the west by North Dakota and South Dakota. In addition, Minnesota shares a water boundary with Michigan. Minnesota is the northernmost of the 48 contiguous states (Alaska reaches significantly farther north), reaching to 49° 23' 04" north latitude, due to a small piece of the state known as the Northwest Angle. Minnesota sits at a convergence point between three of the great biomes of North America: the Great Plains of the west, the Eastern Deciduous Forest, and the Northern Boreal Forest of Canada. Traversing the state from southwest to northeast, one goes through the three different ecological regions. The capital is St. Paul, which sits on the Mississippi River next to Minnesota's largest city, Minneapolis. Together (and with surrounding suburbs), they are known as the Twin Cities. Other prominent cities include Duluth, St. Cloud, Mankato, Rochester (home of the world-famous Mayo Clinic), and Bloomington (home to the Mall of America). The state's average elevation is 1,200 feet (366 m), with a high point at Eagle Mountain (Minnesota) (2,301 ft or 701 m) and a low at the surface of Lake Superior (602 ft or 183 m). Aside from a few very minor earthquakes, Minnesota is one of the most geologically-stable regions in the country. The biggest earthquake in the last century occurred near Morris in 1975 and rated between 4.6 and 4.8 in magnitude. Temperatures can reach extremes in Minnesota. The northern part of the state is famously cold in winter, with a record low of -60 °F (-51 °C) measured at Tower, MN on February 2, 1996. Surprisingly, due to the flows of the jet stream, parts of Alaska often see relatively warm temperatures when Minnesota is experiencing extreme cold. Additionally, as part of the Great Plains region, the state also experiences warm summers. A record high of 114 °F (45.5 °C) was reached in both 1917 and 1936. The average temperature in January (the coldest month) is 11.2 °F (-11.5 °C), and the average in the warmest month, July, is 73.1 °F (22.8 °C); averages are cooler in the north and warmer in the south. The average annual precipitation is 28.32 inches (719 mm), with a snowfall figure of 49.6 inches (126 cm).

Economy

The Bureau of Economic Analysis estimates that Minnesota's total state product in 2003 was $211 billion. Per capita personal income in 2003 was $34,031, 10^th in the nation. The average household income in 1999 was approximately $48,000, ranking eighth in the nation (U.S. Census Bureau). The county averages range from $17,369 (Todd County) to $42,313 (Hennepin County, a portion of the Metro area). In general, salaries are lowest in more rural areas, particularly in the northwest portion of the state.

Major industries/products

The Twin Cities are home to a diverse range of major businesses, including Cargill, 3M Co. (formerly Minnesota Mining and Manufacturing Co.), Northwest Airlines, Target Corporation, U.S. Bancorp, Thrivent Financial for Lutherans (the merged entity of the former Aid Association for Lutherans and Lutheran Brotherhood), Medtronic, Ecolab, Best Buy, Cray Computers, Imation, International Dairy Queen, Regis Corporation, General Mills and a regional headquarters of Wells Fargo & Co., Caterpillar Inc. and Honeywell. The city of Rochester is the headquarters of the Mayo Clinic, and has a significant manufacturing presence in International Business Machines. The largest shopping mall in the United States, the Mall of America, is located in Bloomington. The Schwan Food Company, headquartered in Marshall, Minn., is one of the largest, branded frozen-food companies in the United States and the second-largest privately-held corporation in Minnesota. The state has been a major influence in the area of transportation, moving products along the Mississippi River, in and out of the inland seaport of Duluth, along railroads that crisscross the state, via highways with trucking and busing companies, and through the air with a major airline hub. However, water- and rail-borne traffic has been declining steadily over the years. A large proportion of the state's economy is still agricultural, even though only a small percentage of the population (around 2%) consider themselves to be farmers. Additionally, northern Minnesota is a source for iron ore and wood products, though these are both declining industries. The agricultural community is also strongly tied to the renewable energy market in the state.

Energy use and production

A fair amount of ethanol alcohol fuel is produced in the state, and a 10% mix of ethanol into consumer gasoline has been mandated since 1997 (as of 2004, Minnesota is the only U.S. state with such a mandate). A 2% biodiesel blend has also been required in diesel fuel since 2005. Many farmers also now operate wind turbines to produce electricity, particularly in the windy southwest region. As of January 2005, the state is the country's fourth-largest wind energy producer after California, Texas, and Iowa, with 615 megawatts installed and 213 MW planned [http://www.awea.org/projects/]. Like many Midwestern states, Minnesota is heavily dependent on natural gas for home heating. Just over two-thirds of homes use the fuel. The state doesn't produce any petroleum of its own, but boasts the largest oil refinery of any non-oil-producing state, the Pine Bend Refinery. One of the longest pipelines in the world, the Lakehead Pipeline, also traverses northern Minnesota. Most of the petroleum used in the state comes from Canada and the northwestern United States.

State taxes

Minnesota is regarded as a high-tax state by some. It has an income and sales tax, as well as levying taxes on a common range of goods such as tobacco, gasoline, and alcohol. The state does not charge sales tax on clothing, services (massages, haircuts, auto work, etc), or food] items, excluding some specific items such as [[candy]]. According to state law, "Candy does not include any preparation containing [[flour and must require no refrigeration." ([http://www.revisor.leg.state.mn.us/data/revisor/statutes/2005/297A/61.html Minn Stat 297A.66 Subd 33]) Minnesota businesses and individuals paid an average of 11.8% of their income in state and local taxes in 1998, down from 12.7% in 1996 (Minnesota Department of Revenue). The Gross State Product was just under $173 billion in 1999 (Northeast Midwest Institute), with approximately $17.5 billion in exports in 2000. Retail sales per capita were $10,260 in 1997, higher than the U.S. average of $9,190 (U.S. Census Bureau). The "retail capital" of the state is probably the Twin Cities suburb of Roseville, which recorded $14,870 per capita (though it is easily outstripped in total revenue by Minneapolis, St. Paul, Bloomington, and Edina).

Demographics

As of 2004, the state's population was estimated to be 5,100,958 (1.75% of the total national population), the population had increased 725,000 since 1990, or 16.6% (compared to 18.5% for the nation). 6.1% of Minnesota residents are foreign-born (compared to 11.1% for the nation) Most of the state's population is centered in the Twin Cities metropolitan area. Race
The racial makeup of the state:
- 88.2% White
- 3.5% Black
- 2.9% Hispanic
- 2.9% Asian
- 1.1% Native American
- 1.4% Mixed race

Ethnic groups/Ancestry groups

According to the 2002 U.S. Census, the largest reported ancestries are German (36.7%), Norwegian (17.2%), Irish (11.2%), and English (6.3%). More recent immigrant communities include the third-largest Hmong population in the United States (from the Laos/Thailand/Vietnam region) and the second largest urban center of Hmong population in the world (concentrated in St. Paul), and a large community of Somali refugees.

Population distribution

The population distribution by age is (Northeast Midwest Institute):
- 0-18 - 1,361,616 (27.7%)
- 19-34 - 1,068,850 (21.7%)
- 35-64 - 1,894,747 (38.6%)
- 65+ - 594,266 (12.1%)

Religion

Most Minnesotans (Nearly 6 in 10) are Protestants (mostly mainline Protestant), although there is also a moderate-sized Roman Catholic community (about one-fourth of the state population). The largest Protestant denomination in the state is Lutheranism. In recent years, new immigrants have added new religions to Minnesota, and there are now Islamic mosques, Buddhist temples, and Hindu mandirs in the state (mainly in the Minneapolis-St. Paul metropolitan area), however the number of Minnesotans who adhere to non-Christian religions is still low. Religious Affiliations in Minnesota:
- Christian – 84%
- Protestant – 58%
- Lutheran – 26%
- Baptist – 5%
- Methodist – 4%
- Presbyterian – 3%
- Other Protestant – 20%
- Roman Catholic – 25%
- Other Christian – 1%
- Other religions – 1%
- Not religious/Agnostic – 15%

Education

Colleges and universities

Wisconsin

:This article is on the U.S. state. For other uses see Wisconsin (disambiguation) Wisconsin is a state in the United States, located in the Midwest. Although the exact etymology of the name is uncertain, "Wisconsin" is thought to be an English version of a French adaptation of an Indian word. The Ojibwe word Miskasinsin, meaning "Red-stone place," was probably the name given to the Wisconsin River, which then was recorded as Ouisconsin by the French, and changed to its current form by the English. Other theories are that the name comes from words meaning "Gathering of the Waters" or "Great Rock." Wisconsin originally was applied to the Wisconsin River, and later to the area as a whole when Wisconsin became a territory. The state's name is abbreviated WI, Wis, or Wisc. USS Wisconsi