1.
Glacial period
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A glacial period is an interval of time within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the hand, are periods of warmer climate between glacial periods. The last glacial period ended about 15,000 years ago, the Holocene epoch is the current interglacial. A time when there are no glaciers on Earth is considered a greenhouse climate state, within the Quaternary glaciation, there have been a number of glacials and interglacials. The last glacial period was the most recent glacial period within the current ice age, occurring in the Pleistocene epoch, the glacial advance reached its maximum extent about 18,000 BP. In Europe, the ice sheet reached northern Germany, since orbital variations are predictable, computer models that relate orbital variations to climate can predict future climate possibilities. Work by Berger and Loutre suggests that the current warm climate may last another 50,000 years
2.
Outburst flood
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In geomorphology, an outburst flood, which is a type of megaflood, is a high-magnitude, low-frequency catastrophic flood involving the sudden release of water. During the last deglaciation, numerous glacial lake outburst floods were caused by the collapse of ice sheets or glaciers that formed the dams of proglacial lakes. Examples of older outburst floods are known from the geological past of the Earth, landslides, lahars, and volcanic dams can also block rivers and create lakes, which trigger such floods when the rock or earthen barrier collapses or is eroded. Lakes also form behind glacial moraines, which can collapse and create outburst floods, megafloods are paleofloods that involved rates of water flow larger than those in the historical record. They are studied through the deposits and the erosional and constructional landforms that individual megafloods have created. Floods that are known to us through historical descriptions are related to meteorological events, such as heavy rains, rapid melting of snowpacks. In the geological past of the Earth, however, geological research has shown much larger events have occurred. In the case of outburst floods, such floods are typically linked to the collapse of the forming a lake. They fall in the classification according to the mechanism responsible. Rapid erosion, melting of ice sheets, Collapse of volcanic dams created by lava flows, lahars, or pyroclastic flows. Overtopping of earthen or rock barriers Lake overtopping, Ocean spilling over a dividing ridge into a landlocked basin. A smaller scale example would be the Pantai Remis landslide, a landslide dam on Sichuans Dadu River, created by an earthquake ten days earlier, burst and caused a flood that extended 1400 km downstream and killed 100,000 people. The marine incursion, caused by the level of the Mediterranean. In North America, during glacial maximum, there were no Great Lakes as we know them and they lay in the areas of the modern lakes, but their drainage sometimes passed south, into the Mississippi system, sometimes into the Arctic, or east into the Atlantic. The most famous of these lakes was Lake Agassiz. As ice-dam configurations failed, a series of floods were released from Lake Agassiz. The Missoula Floods of Oregon and Washington states were caused by breaking ice dams. Lake Bonneville was not a lake, but glacial age climate change determined the lake level
3.
Icelandic language
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Icelandic /aɪsˈlændɪk/ is a North Germanic language, the language of Iceland. It is an Indo-European language belonging to the North Germanic or Nordic branch of the Germanic languages, historically, it was the westernmost of the Indo-European languages prior to the colonisation of the Americas. Icelandic, Faroese, Norn, and Western Norwegian formerly constituted West Nordic, Danish, Eastern Norwegian, modern Norwegian Bokmål is influenced by both groups, leading the Nordic languages to be divided into mainland Scandinavian languages and Insular Nordic. Most Western European languages have reduced levels of inflection, particularly noun declension. In contrast, Icelandic retains a four-case synthetic grammar comparable to, Icelandic is distinguished by a wide assortment of irregular declensions. Icelandic also has many instances of oblique cases without any governing word, for example, many of the various Latin ablatives have a corresponding Icelandic dative. The vast majority of Icelandic speakers—about 320, 000—live in Iceland, more than 8,000 Icelandic speakers live in Denmark, of whom approximately 3,000 are students. The language is spoken by some 5,000 people in the United States. Notably in the province of Manitoba, while 97% of the population of Iceland consider Icelandic their mother tongue, the language is in decline in some communities outside Iceland, particularly in Canada. Icelandic speakers outside Iceland represent recent emigration in almost all cases except Gimli, Manitoba, the state-funded Árni Magnússon Institute for Icelandic Studies serves as a centre for preserving the medieval Icelandic manuscripts and studying the language and its literature. Since 1995, on 16 November each year, the birthday of 19th-century poet Jónas Hallgrímsson is celebrated as Icelandic Language Day, the oldest preserved texts in Icelandic were written around 1100 AD. Much of the texts are based on poetry and laws traditionally preserved orally, the most famous of the texts, which were written in Iceland from the 12th century onward, are the Icelandic Sagas. They comprise the historical works and the eddaic poems, the language of the sagas is Old Icelandic, a western dialect of Old Norse. Danish rule of Iceland from 1380 to 1918 had little effect on the evolution of Icelandic, though more archaic than the other living Germanic languages, Icelandic changed markedly in pronunciation from the 12th to the 16th century, especially in vowels. The modern Icelandic alphabet has developed from an established in the 19th century. The later Rasmus Rask standard was a re-creation of the old treatise, with changes to fit concurrent Germanic conventions. Various archaic features, as the letter ð, had not been used much in later centuries, rasks standard constituted a major change in practice. Later 20th-century changes include the use of é instead of je, apart from the addition of new vocabulary, written Icelandic has not changed substantially since the 11th century, when the first texts were written on vellum
4.
Glaciology
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Glaciology is the scientific study of glaciers, or more generally ice and natural phenomena that involve ice. Glaciology is an earth science that integrates geophysics, geology, physical geography, geomorphology, climatology, meteorology, hydrology, biology. The impact of glaciers on people includes the fields of human geography, the discoveries of water ice on the Moon, Mars, Europa and Pluto add an extraterrestrial component to the field, as in astroglaciology. Areas of study within glaciology include glacial history and the reconstruction of past glaciation, a glaciologist is a person who studies glaciers. A glacial geologist studies glacial deposits and glacial erosive features on the landscape, glaciology and glacial geology are key areas of polar research. Alpine - ice flows down the valleys of mountainous areas and forms a tongue of ice moving towards the plains below, continental - an ice sheet found today, only in high latitudes, thousands of square kilometers in area and thousands of meters thick. These tend to smooth out the landscapes, accumulation, where the formation of ice is faster than its removal. Wastage or ablation, where the sum of melting and evaporation is greater than the amount of snow added each year, ablation wastage of the glacier through sublimation, ice melting and iceberg calving. Ablation zone Area of a glacier in which the loss of ice through ablation exceeds the annual gain from precipitation. Arête an acute ridge of rock where two cirques abut, bergschrund crevasse formed near the head of a glacier, where the mass of ice has rotated, sheared and torn itself apart in the manner of a geological fault. Cirque, corrie or cwm bowl shaped depression excavated by the source of a glacier, creep adjustment to stress at a molecular level. Flow movement in a constant direction, fracture brittle failure under the stress raised when movement is too rapid to be accommodated by creep. It happens for example, as the part of a glacier moves faster than the edges. Horn spire of rock, also known as a pyramidal peak and it is an extreme case of an arête. Plucking/Quarrying where the adhesion of the ice to the rock is stronger than the cohesion of the rock, tarn a post-glacial lake in a cirque. Tunnel valley The tunnel that is formed by erosion of ice. The tunnel valley is what remains of it in the rock when the ice sheet has melted. Movement of the glacier is very slow and its velocity varies from a few centimeters per day to a few meters per day
5.
Iceland
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Iceland is a Nordic island country in the North Atlantic Ocean. It has a population of 332,529 and an area of 103,000 km2, the capital and largest city is Reykjavík. Reykjavík and the areas in the southwest of the country are home to over two-thirds of the population. Iceland is volcanically and geologically active, the interior consists of a plateau characterised by sand and lava fields, mountains and glaciers, while many glacial rivers flow to the sea through the lowlands. Iceland is warmed by the Gulf Stream and has a climate, despite a high latitude just outside the Arctic Circle. Its high latitude and marine influence still keeps summers chilly, with most of the archipelago having a tundra climate. According to the ancient manuscript Landnámabók, the settlement of Iceland began in the year 874 AD when the Norwegian chieftain Ingólfr Arnarson became the first permanent settler on the island. In the following centuries, Norwegians, and to a lesser extent other Scandinavians, emigrated to Iceland, the island was governed as an independent commonwealth under the Althing, one of the worlds oldest functioning legislative assemblies. Following a period of strife, Iceland acceded to Norwegian rule in the 13th century. The establishment of the Kalmar Union in 1397 united the kingdoms of Norway, Denmark, Iceland thus followed Norways integration to that Union and came under Danish rule after Swedens secession from that union in 1523. In the wake of the French revolution and the Napoleonic wars, Icelands struggle for independence took form and culminated in independence in 1918, until the 20th century, Iceland relied largely on subsistence fishing and agriculture, and was among the poorest in Europe. Industrialisation of the fisheries and Marshall Plan aid following World War II brought prosperity, in 1994, it became a part of the European Economic Area, which further diversified the economy into sectors such as finance, biotechnology, and manufacturing. Iceland has an economy with relatively low taxes compared to other OECD countries. It maintains a Nordic social welfare system that provides health care. Iceland ranks high in economic, political and social stability and equality, in 2013, it was ranked as the 13th most-developed country in the world by the United Nations Human Development Index. Iceland runs almost completely on renewable energy, some bankers were jailed, and the economy has made a significant recovery, in large part due to a surge in tourism. Icelandic culture is founded upon the nations Scandinavian heritage, most Icelanders are descendants of Germanic and Gaelic settlers. Icelandic, a North Germanic language, is descended from Old Norse and is related to Faroese
6.
Subglacial eruption
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Subglacial eruptions, those of ice-covered volcanoes, result in the interaction of magma with ice and snow, leading to meltwater formation, jökulhlaups, and lahars. Flooding associated with meltwater is a significant hazard in some areas, including Iceland, Alaska. It is important to explore volcano-ice interactions to improve our ability to monitor these events. The resulting flood severely damaged buildings on the island, with destruction of a British scientific station. Over a period of 13 days,3 km2 of ice was melted with erupted magma fracturing into glass to form a 7 km long and 300 m high hyaloclastite ridge under 750 m of ice. Meltwater flowed along a narrow basal glacier bed into a lake for five weeks, before being released as a sudden flood. Research demonstrated that for warm-based glaciers, the effects of volcanic eruptions are localised, with eruptions forming deep depressions. In the first two days of the eruption, ice cauldrons were formed over the volcanic vents, radar images reveal the development of these cauldrons in a 200 m thick ice cover within the summit caldera. They can also be used to document the subglacial and supraglacial passage of meltwater away from the eruption site
7.
Subglacial lake
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A subglacial lake is a lake under a glacier, typically an ice cap or ice sheet. There are many lakes, with Lake Vostok in Antarctica being by far the largest known at present. The water below the ice remains liquid since geothermal heating balances the loss at the ice surface. The pressure causes the point of water to be below 0°C. The ceiling of the lake will be at the level where the pressure melting point of water intersects the temperature gradient. In Lake Vostok the ice over the lake is much thicker than the ice sheet around it. The water in the lake can have a level much above the level of the ground threshold. In fact, theoretically a sub-glacial lake can even exist on the top of a hill, the floating level can be thought of as the water level in a hole drilled through the ice into the lake. It is equivalent to the level at which a piece of the ice over it would if it were a normal ice shelf. The ceiling can therefore be conceived as an ice shelf that is grounded along its entire perimeter, as it moves over the lake, it enters the lake at the floating line, and it leaves the lake at the grounding line. For the lake to exist there must be a hydrostatic seal along the entire perimeter, a hydrostatic seal is created when the ice is so much higher around the lake that the equipotential surface dips down into impermeable ground. Water from underneath this ice rim is then pressed back into the lake by the hydrostatic seal, the ice surface is ten times more important than the bed surface in creating the hydrostatic seal. This means that a 1 m rise in the ice surface at the ice rim is as efficient as a 10 m rise in the bed level below it. In Lake Vostok the ice rim has been estimated to a mere 7 m, if the hydrostatic seal is penetrated when the floating level is high, the water will start flowing out in a jökulhlaup. Due to melting of the channel the discharge increases exponentially, unless other processes allow the discharge to increase even faster, due to the high head that can be achieved in subglacial lakes, jökulhlaups may reach very high rates of discharge. Russian scientist Peter Kropotkin first proposed the idea of water under Antarctic ice sheets at the end of the 19th century. Kropotkins theory was developed by Russian glaciologist I. A Zotikov. Andrey Kapitsa used seismic soundings in the region of Vostok Station made during the Soviet Antarctic Expeditions in 1959 and 1964 to measure the thickness of the ice sheet
8.
Proglacial lake
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At the end of the last ice age approximately 10,000 years ago, large proglacial lakes were a widespread feature in the northern hemisphere. In some cases, such lakes gradually evaporated during the period after the Quaternary ice age. Good examples of structures can be found in the Channeled Scablands of eastern Washington. In Great Britain, Lake Lapworth, Lake Harrison and Lake Pickering were examples of proglacial lakes, the receding glaciers of the tropical Andes have formed a number of proglacial lakes, especially in the Cordillera Blanca of Peru, where 70% of all tropical glaciers are. Several such lakes have formed rapidly during the 20th century and these lakes may burst, creating a hazard for zones below. Many natural dams containing the water have been reinforced with safety dams. Some 34 such dams have been built in the Cordillera Blanca to contain proglacial lakes, several proglacial lakes have also formed in recent decades at the end of glaciers on the eastern side of New Zealands Southern Alps. The most accessible, Lake Tasman, hosts boat trips for tourists, list of prehistoric lakes Pluvial lake Proglacial lakes of Minnesota
9.
Hydrostatics
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Fluid statics or hydrostatics is the branch of fluid mechanics that studies incompressible fluids at rest. It encompasses the study of the conditions under which fluids are at rest in stable equilibrium as opposed to fluid dynamics, hydrostatics are categorized as a part of the fluid statics, which is the study of all fluids, incompressible or not, at rest. Hydrostatics is fundamental to hydraulics, the engineering of equipment for storing, transporting and using fluids and it is also relevant to geophysics and astrophysics, to meteorology, to medicine, and many other fields. Some principles of hydrostatics have been known in an empirical and intuitive sense since antiquity, by the builders of boats, cisterns, aqueducts and fountains. Archimedes is credited with the discovery of Archimedes Principle, which relates the force on an object that is submerged in a fluid to the weight of fluid displaced by the object. The fair cup or Pythagorean cup, which dates from about the 6th century BC, is a technology whose invention is credited to the Greek mathematician. It was used as a learning tool, the cup consists of a line carved into the interior of the cup, and a small vertical pipe in the center of the cup that leads to the bottom. The height of this pipe is the same as the line carved into the interior of the cup, the cup may be filled to the line without any fluid passing into the pipe in the center of the cup. However, when the amount of fluid exceeds this fill line, due to the drag that molecules exert on one another, the cup will be emptied. Herons fountain is a device invented by Heron of Alexandria that consists of a jet of fluid being fed by a reservoir of fluid. The fountain is constructed in such a way that the height of the jet exceeds the height of the fluid in the reservoir, the device consisted of an opening and two containers arranged one above the other. The intermediate pot, which was sealed, was filled with fluid, trapped air inside the vessels induces a jet of water out of a nozzle, emptying all water from the intermediate reservoir. Pascal made contributions to developments in both hydrostatics and hydrodynamics, due to the fundamental nature of fluids, a fluid cannot remain at rest under the presence of a shear stress. However, fluids can exert pressure normal to any contacting surface, if a point in the fluid is thought of as an infinitesimally small cube, then it follows from the principles of equilibrium that the pressure on every side of this unit of fluid must be equal. If this were not the case, the fluid would move in the direction of the resulting force, thus, the pressure on a fluid at rest is isotropic, i. e. it acts with equal magnitude in all directions. This characteristic allows fluids to transmit force through the length of pipes or tubes, i. e. a force applied to a fluid in a pipe is transmitted, via the fluid, to the other end of the pipe. This principle was first formulated, in an extended form, by Blaise Pascal. In a fluid at rest, all frictional and inertial stresses vanish, when this condition of V =0 is applied to the Navier-Stokes equation, the gradient of pressure becomes a function of body forces only
10.
Discharge (hydrology)
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In hydrology, discharge is the volume rate of water flow that is transported through a given cross-sectional area. It includes any suspended solids, dissolved chemicals, or biologic material in addition to the water itself, GH Dury and MJ Bradshaw are two hydrologists who devised the models showing the relationship between discharge and other variables in a river. The units that are used to express discharge include m³/s, ft³/s and/or acre-feet per day. For example, the discharge of the Rhine river in Europe is 2,200 cubic metres per second or 190,000,000 cubic metres per day. A commonly applied methodology for measuring, and estimating, the discharge of a river is based on a form of the continuity equation. In storm hydrology, an important consideration is the streams discharge hydrograph, the stream rises to a peak flow after each precipitation event, then falls in a slow recession. Because the peak flow also corresponds to the water level reached during the event. The amount of precipitation correlates to the volume of water that flows out of the river. The relationship between the discharge in the stream at a given cross-section and the level of the stream is described by a rating curve, average velocities and the cross-sectional area of the stream are measured for a given stream level. The velocity and the give the discharge for that level. After measurements are made for different levels, a rating table or rating curve may be developed. Once rated, the discharge in the stream may be determined by measuring the level, if a continuous level-recording device is located at a rated cross-section, the streams discharge may be continuously determined. Larger flows can transport more sediment and larger particles downstream than smaller flows due to their greater force, larger flows can also erode stream banks and damage public infrastructure
11.
Hydrograph
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A hydrograph is a graph showing the rate of flow versus time past a specific point in a river, or other channel or conduit carrying flow. The rate of flow is typically expressed in meters or cubic feet per second. It can also refer to a showing the volume of water reaching a particular outfall. Graphs are commonly used in the design of sewerage, more specifically, the discharge is measured at a specific point in a river and is typically time variant. The end of stormflow and the return to groundwater-derived flow is taken as the point of inflection of the recession limb. The recession limb represents the withdrawal of water from the built up in the basin during the earlier phases of the hydrograph. k. a. However, the process of separating “baseflow” from “direct runoff” is an inexact science, in part this is because these two concepts are not, themselves, entirely distinct and unrelated. Therefore, separation of a purely “baseflow component” in a hydrograph is a somewhat arbitrary exercise, nevertheless, various graphical and empirical techniques have been developed to perform these hydrograph separations. A unit hydrograph is the hypothetical unit response of a watershed to an input of rainfall. It can be defined as the runoff hydrograph resulting from one unit of effective rainfall occurring uniformly over that watershed at a uniform rate over a unit period of time. As a UH is applicable only to the direct component of a hydrograph. A UH is specific to a watershed, and specific to a particular length of time corresponding to the duration of the effective rainfall. That is, the UH is specified as being the 1-hour, 6-hour, or 24-hour UH, thus, for a given watershed, there can be many unit hydrographs, each one corresponding to a different duration of effective rainfall. The UH technique provides a practical and relatively easy-to-apply tool for quantifying the effect of a unit of rainfall on the runoff from a particular drainage basin. UH theory assumes that a watersheds runoff response is linear and time-invariant, in the real world, none of these assumptions are strictly true. Nevertheless, application of UH methods typically yields an approximation of the flood response of natural watersheds. This allows for a straightforward calculation of the hydrograph response to any arbitrary rain event. An instantaneous unit hydrograph is a refinement of the concept, for an IUH
12.
Last glacial period
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The last glacial period, popularly known as the Ice Age, was the most recent glacial period, which occurred from c. 110,000 – c. 11,700 years ago. This most recent glacial period is part of a pattern of glacial and interglacial periods known as the Quaternary glaciation. From this point of view, scientists consider this ice age to be merely the latest glaciation event in a larger ice age. During this last glacial period, there were changes between glacier advance and retreat. The Last Glacial Maximum, the extent of glaciation within the last glacial period, was approximately 22,000 years ago. Approximately 13,000 years ago, the Late Glacial Maximum began, around 11,700 years ago marked the beginning of the Holocene geological epoch, which includes the Holocene glacial retreat. From the point of view of archaeology, it falls in the Paleolithic and Mesolithic periods. When the glaciation event started, Homo sapiens were confined to Africa and used tools comparable to those used by Neanderthals in western and central Eurasia, near the end of the event, Homo sapiens spread into Eurasia and Australia. The retreat of the glaciers allowed groups of Asians to migrate to the Americas, glacials, on the other hand, refer to colder phases within an ice age that separate interglacials. Thus, the end of the last glacial period is not the end of the last ice age, the end of the last glacial period was about 11,700 years ago, while the end of the last ice age has not yet come. Over the past few years the glacial-interglacial cycle has been paced by periodic variations in the Earths orbit via Milankovitch cycles which are thus the cause of ice ages. The glaciations that occurred during this period covered many areas, mainly in the Northern Hemisphere. The geochronological Late Pleistocene comprises the late glacial and the immediately preceding penultimate interglacial preiond, the last glaciation centered on the huge ice sheets of North America and Eurasia. Considerable areas in the Alps, the Himalaya and the Andes were ice-covered, Canada was nearly completely covered by ice, as well as the northern part of the United States, both blanketed by the huge Laurentide ice sheet. Alaska remained mostly ice free due to climate conditions. Local glaciations existed in the Rocky Mountains and the Cordilleran ice sheet and as ice fields, the maximum extent of western Siberian glaciation was reached by approximately 16, 000–15,000 BCE and thus later than in Europe. Northeastern Siberia was not covered by an ice sheet. Instead, large, but restricted, icefield complexes covered mountain ranges within northeast Siberia, according to the sediment composition retrieved from deep-sea cores there must even have been times of seasonally open waters
13.
Lake Agassiz
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Lake Agassiz was a very large glacial lake located in the middle of the northern part of North America. First postulated in 1823 by William H. Keating, it was named by Warren Upham in 1879 after Louis Agassiz, during the last Ice Age, northern North America was covered by a glacier, which alternately advanced and melted with variations in the climate. This continental ice sheet formed during the now known as the Wisconsin glaciation. Around 13,000 years ago, the lake came to much of Manitoba, northwestern Ontario, northern Minnesota, eastern North Dakota. At its greatest extent, it may have covered as much as 440,000 km2, larger than any currently existing lake in the world and approximately the size of the Black Sea. Geologists have found evidence that an outbreak of Lake Agassiz, about 13,000 years ago. A return of the ice for some time offered a reprieve, the last major shift in drainage occurred around 8,200 years ago. The melting of remaining Hudson Bay ice caused Lake Agassiz to drain nearly completely and this final drainage of Lake Agassiz is associated with an estimated 0.8 to 2.8 m rise in global sea levels. Lake Agassizs major drainage reorganization events were of such magnitudes that they had significant impact on climate, sea level, major freshwater release into the Arctic Ocean is considered to disrupt oceanic circulation and cause temporary cooling. The draining of 13,000 years ago may be the cause of the Younger Dryas stadial, the draining at 9, 900–10,000 years ago may be the cause of the 8,200 yr climate event. The lowest point between the drainage of Hudson Bay and the Gulf of Mexico is in the Traverse Gap between the U. S. states of Minnesota and South Dakota and it lies between Lake Traverse and Big Stone Lake. This subcontinental divide is about 300 metres above sea level, when Lake Agassiz existed the gap was the outlet of River Warren. The outflow from the melting glaciers filled Lake Agassiz and then drained through the gap to the Gulf of Mexico and this mass of moving water eroded a valley about 2–5 kilometres wide and from 100 feet to 125 feet deep. Today, this contains the Minnesota River, joined by the Upper Mississippi River at Mendota, Minnesota. The northern part of the lakebed is the valley of the Red River of the North. In the following sections, YBP denotes years before present, during the Lockhart Phase, water accumulated in the Red River valley of North Dakota and Minnesota. As the water reached to the top of the divide to the south and this occurred while the Laurentian Ice Sheet was at or below the current Canada–US border. As the ice sheet melted northward, an early Lake Agassiz covered southern Manitoba, the Minnesota and Ontario boundary country, the Lockhart phase is associated with the Herman lake stage, the highest shoreline of Lake Agassiz
14.
English Channel
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The English Channel, also called simply the Channel, is the body of water that separates southern England from northern France, and links the southern part of the North Sea to the Atlantic Ocean. It is about 560 km long and varies in width from 240 km at its widest to 33.3 km in the Strait of Dover and it is the smallest of the shallow seas around the continental shelf of Europe, covering an area of some 75,000 km2. The International Hydrographic Organization defines the limits of the English Channel as follows, a line joining Isle Vierge to Lands End. The southwestern limit of the North Sea, the IHO defines the southwestern limit of the North Sea as a line joining the Walde Lighthouse and Leathercoat Point. The Walde Lighthouse is 6 km east of Calais, and Leathercoat Point is at the end of St Margarets Bay. The Strait of Dover, at the Channels eastern end, is its narrowest point and it is relatively shallow, with an average depth of about 120 m at its widest part, reducing to a depth of about 45 m between Dover and Calais. Eastwards from there the adjoining North Sea reduces to about 26 m in the Broad Fourteens where it lies over the watershed of the land bridge between East Anglia and the Low Countries. It reaches a depth of 180 m in the submerged valley of Hurds Deep,48 km west-northwest of Guernsey. The eastern region along the French coast between Cherbourg and the mouth of the Seine river at Le Havre is frequently referred to as the Bay of the Seine. There are several islands in the Channel, the most notable being the Isle of Wight off the English coast. The coastline, particularly on the French shore, is indented, several small islands close to the coastline, including Chausey. The Cotentin Peninsula in France juts out into the Channel, whilst on the English side there is a parallel channel known as the Solent between the Isle of Wight and the mainland. The Celtic Sea is to the west of the Channel, the time difference of about six hours between high water at the eastern and western limits of the Channel is indicative of the tidal range being amplified further by resonance. It was never defined as a border and the names were more or less descriptive. It was not considered as the property of a nation, strangely, before the development of the modern nations, British scholars very often referred to it as Gaulish and the French one as British or English. The name English Channel has been used since the early 18th century. In modern Dutch, however, it is known as Het Kanaal, later, it has also been known as the British Channel or the British Sea having been called the Oceanus Britannicus by the 2nd-century geographer Ptolemy. The same name is used on an Italian map of about 1450, the Anglo-Saxon texts often call it Sūð-sǣ as opposed to Norð-sǣ
15.
Ablation
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Ablation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes. Biological ablation is the removal of a structure or functionality. Genetic ablation is another term for gene silencing, in gene expression is abolished through the alteration or deletion of genetic sequence information. In cell ablation, individual cells in a population or culture are destroyed or removed, both can be used as experimental tools, as in loss-of-function experiments. In glaciology and meteorology, ablation—the opposite of accumulation—refers to all processes that remove snow, ice, Ablation refers to the melting of snow or ice that runs off the glacier, evaporation, sublimation, calving, or erosive removal of snow by wind. Air temperature is typically the dominant control of ablation, with precipitation exercising secondary control, in a temperate climate during ablation season, ablation rates typically average around 2 mm/h. Where solar radiation is the dominant cause of snow ablation, characteristic ablation textures such as suncups, Ablation can refer either to the processes removing ice and snow or to the quantity of ice and snow removed. Laser ablation is greatly affected by the nature of the material and its ability to absorb energy, since the cornea does not grow back, laser is used to remodel the cornea refractive properties to correct refraction errors, such as astigmatism, myopia, and hyperopia. Laser ablation is used to remove part of the uterine wall in women with menstruation. Ablative paints are often utilized for this purpose to prevent the dilution or deactivation of the antifouling agent, over time, the paint will slowly decompose in the water, exposing fresh antifouling compounds on the surface. Engineering the antifouling agents and the rate can produce long-lived protection from the deleterious effects of biofouling. In medicine, ablation is the same as removal of a part of biological tissue, surface ablation of the skin can be carried out by chemicals, by lasers, or by electricity. Its purpose is to remove skin spots, aged skin, wrinkles, surface ablation is also employed in otolaryngology for several kinds of surgery, such as for snoring. The term is used in the context of laser ablation. For a laser to ablate tissues, the density or fluence must be high, otherwise thermocoagulation occurs. Rotoablation is a type of arterial cleansing that consists of inserting a tiny, diamond-tipped, the procedure is used in the treatment of coronary heart disease to restore blood flow. Radiofrequency ablation is a method of removing aberrant tissue from within the body via minimally invasive procedures, microwave ablation is similar to RFA but at higher frequency of electromagnetic radiation. Bone marrow ablation is a process whereby the human bone marrow cells are eliminated in preparation for a marrow transplant
16.
Weichselian glaciation
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In the Alpine region it corresponds to the Würm glaciation. It was characterised by an ice sheet that spread out from the Scandinavian Mountains and extended as far as the east coast of Schleswig-Holstein. In Northern Europe it was the youngest of the glacials of the Pleistocene ice age, the preceding warm period in this region was the Eemian interglacial. The last cold period began about 115,000 years ago and its end corresponds with the end of the Pleistocene epoch and start of the Holocene. About 115,000 years ago average temperatures dropped markedly and warmth-loving woodland species were displaced and this significant turning point in average temperatures marked the end of the Eemian interglacial and start of the Weichselian glacial stage. It is divided into three sections, based on the variation, the Weichselian Early Glacial, the Weichselian High Glacial. During the Weichselian, there were frequent major variations in climate in the northern hemisphere, the Weichsel Early Glacial is in turn divided into four stages, Odderade Interstadial. The pollen spectra indicate a boreal forest and it starts with a tree birch phase, which rapidly transitions to pine forest. Also apparent are larches and spruce as well as low numbers of alder, in North Germany the pollen spectra indicate a grassy tundra followed later by shrubby tundra. Several profiles show a period of cooling shortly after the start of the Brörup Interstadial. This led some authors to distinguish the first warm period as the Amersfoort Interstadial, however, since then, this first warm period and cooling phase has been included in the Brörup Interstadial. Northern Central Europe was populated by birch and pine woods, the Brörup Interstadial is identified with marine isotope stage 5c. The Herning Stadial was the first cold phase, in which northwestern Europe was largely treeless and it corresponds to marine isotope stage 5d. In the Weichselian High Glacial the ice advanced into North Germany. In this period, however, several interstadials have been documented, glaciation and ice sheet advances to North Germany. The pollen spectra indicates a shrubby tundra landscape, the pollen show sedges and temporarily a high number of dwarf birches. The pollen spectra show a treeless tundra vegetation with a proportion of sedges. The pollen diagrams indicate a treeless, shrubby tundra, in North Germany this period is characterised by pollen-free sands
17.
Aquifer
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An aquifer is an underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials from which groundwater can be extracted using a water well. The study of flow in aquifers and the characterization of aquifers is called hydrogeology. Related terms include aquitard, which is a bed of low permeability along an aquifer, and aquiclude, if the impermeable area overlies the aquifer, pressure could cause it to become a confined aquifer. Aquifers may occur at various depths and those closer to the surface are not only more likely to be used for water supply and irrigation, but are also more likely to be topped up by the local rainfall. Many desert areas have limestone hills or mountains within them or close to them that can be exploited as groundwater resources, overexploitation can lead to the exceeding of the practical sustained yield, i. e. more water is taken out than can be replenished. The beach provides a model to help visualize an aquifer, if a hole is dug into the sand, very wet or saturated sand will be located at a shallow depth. This hole is a well, the wet sand represents an aquifer. In 2013 large freshwater aquifers were discovered under continental shelves off Australia, China, North America and they contain an estimated half a million cubic kilometers of “low salinity” water that could be economically processed into potable water. The reserves formed when ocean levels were lower and rainwater made its way into the ground in areas that were not submerged until the ice age ended 20,000 years ago. The volume is estimated to be 100x the amount of extracted from other aquifers since 1900. The above diagram indicates typical flow directions in a view of a simple confined or unconfined aquifer system. The system shows two aquifers with one aquitard between them, surrounded by the bedrock aquiclude, which is in contact with a gaining stream, the water table and unsaturated zone are also illustrated. An aquitard is a zone within the earth that restricts the flow of groundwater from one aquifer to another, an aquitard can sometimes, if completely impermeable, be called an aquiclude or aquifuge. Aquitards are composed of layers of clay or non-porous rock with low hydraulic conductivity. Groundwater can be found at every point in the Earths shallow subsurface to some degree. Saturated means the head of the water is greater than atmospheric pressure. The definition of the table is the surface where the pressure head is equal to atmospheric pressure. Unsaturated conditions occur above the table where the pressure head is negative
18.
Hydraulic conductivity
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Hydraulic conductivity, symbolically represented as K, is a property of vascular plants, soils and rocks, that describes the ease with which a fluid can move through pore spaces or fractures. It depends on the permeability of the material, the degree of saturation. Saturated hydraulic conductivity, Ksat, describes water movement through saturated media, by definition, hydraulic conductivity is the ratio of velocity to hydraulic gradient indicating permeability of porous media.0 and 1.5, with an average value of 1.0. A. F. Salarashayeri & M. Siosemarde give C as usually taken between 1.0 and 1.5, with D in mm and K in cm/s. There are relatively simple and inexpensive laboratory tests that may be run to determine the conductivity of a soil, constant-head method. The constant-head method is used on granular soil. This procedure allows water to move through the soil under a steady state head condition while the quantity of flowing through the soil specimen is measured over a period of time. The water is allowed to flow through the soil without adding any water. The advantage to the method is that it can be used for both fine-grained and coarse-grained soils. When the water table is shallow, the method, a slug test. The method was developed by Hooghoudt in The Netherlands and introduced in the US by Van Bavel en Kirkham, the picture shows a large variation of K -values measured with the augerhole method in an area of 100 ha. The ratio between the highest and lowest values is 25, the cumulative frequency distribution is lognormal and was made with the CumFreq program. The transmissivity is a measure of how water can be transmitted horizontally. Transmissivity should not be confused with the similar word transmittance used in optics, an aquifer may consist of n soil layers. Expressing K i in m/day and d i in m, the transmissivity T i is found in units m2/day. The total transmissivity T t of the aquifer is, T t = ∑ T i where ∑ signifies the summation over all layers i =1,2,3, ⋯, n, the transmissivity of an aquifer can be determined from pumping tests. Influence of the water table When a soil layer is above the table, it is not saturated. When the soil layer is entirely below the table, its saturated thickness corresponds to the thickness of the soil layer itself
19.
Gravity
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Gravity, or gravitation, is a natural phenomenon by which all things with mass are brought toward one another, including planets, stars and galaxies. Since energy and mass are equivalent, all forms of energy, including light, on Earth, gravity gives weight to physical objects and causes the ocean tides. Gravity has a range, although its effects become increasingly weaker on farther objects. The most extreme example of this curvature of spacetime is a hole, from which nothing can escape once past its event horizon. More gravity results in time dilation, where time lapses more slowly at a lower gravitational potential. Gravity is the weakest of the four fundamental interactions of nature, the gravitational attraction is approximately 1038 times weaker than the strong force,1036 times weaker than the electromagnetic force and 1029 times weaker than the weak force. As a consequence, gravity has an influence on the behavior of subatomic particles. On the other hand, gravity is the dominant interaction at the macroscopic scale, for this reason, in part, pursuit of a theory of everything, the merging of the general theory of relativity and quantum mechanics into quantum gravity, has become an area of research. While the modern European thinkers are credited with development of gravitational theory, some of the earliest descriptions came from early mathematician-astronomers, such as Aryabhata, who had identified the force of gravity to explain why objects do not fall out when the Earth rotates. Later, the works of Brahmagupta referred to the presence of force, described it as an attractive force. Modern work on gravitational theory began with the work of Galileo Galilei in the late 16th and this was a major departure from Aristotles belief that heavier objects have a higher gravitational acceleration. Galileo postulated air resistance as the reason that objects with less mass may fall slower in an atmosphere, galileos work set the stage for the formulation of Newtons theory of gravity. In 1687, English mathematician Sir Isaac Newton published Principia, which hypothesizes the inverse-square law of universal gravitation. Newtons theory enjoyed its greatest success when it was used to predict the existence of Neptune based on motions of Uranus that could not be accounted for by the actions of the other planets. Calculations by both John Couch Adams and Urbain Le Verrier predicted the position of the planet. A discrepancy in Mercurys orbit pointed out flaws in Newtons theory, the issue was resolved in 1915 by Albert Einsteins new theory of general relativity, which accounted for the small discrepancy in Mercurys orbit. The simplest way to test the equivalence principle is to drop two objects of different masses or compositions in a vacuum and see whether they hit the ground at the same time. Such experiments demonstrate that all objects fall at the rate when other forces are negligible
20.
Hydraulic head
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Hydraulic head or piezometric head is a specific measurement of liquid pressure above a geodetic datum. It is usually measured as a surface elevation, expressed in units of length. In an aquifer, it can be calculated from the depth to water in a piezometric well, hydraulic head can similarly be measured in a column of water using a standpipe piezometer by measuring the height of the water surface in the tube relative to a common datum. The hydraulic head can be used to determine a hydraulic gradient between two or more points, in fluid dynamics, head is a concept that relates the energy in an incompressible fluid to the height of an equivalent static column of that fluid. Head is expressed in units of such as meters or feet. The static head of a pump is the height it can deliver. The capability of the pump at a certain RPM can be read from its Q-H curve, a common misconception is that the head equals the fluids energy per unit weight, while, in fact, the term with pressure does not represent any type of energy. Head is useful in specifying centrifugal pumps because their pumping characteristics tend to be independent of the fluids density, there are four types of head used to calculate the total head in and out of a pump, Velocity head is due to the bulk motion of a fluid. Its pressure head correspondent is the dynamic pressure, elevation head is due to the fluids weight, the gravitational force acting on a column of fluid. Pressure head is due to the pressure, the internal molecular motion of a fluid that exerts a force on its container. Resistance head is due to the forces acting against a fluids motion by the container. In a flowing fluid, it represents the energy of the due to its bulk motion. The total hydraulic head of a fluid is composed of pressure head, the pressure head is the equivalent gauge pressure of a column of water at the base of the piezometer, and the elevation head is the relative potential energy in terms of an elevation. The head equation, a form of the Bernoulli Principle for incompressible fluids, can be expressed as, h = ψ + z where h is the hydraulic head. This means that the hydraulic head calculation is dependent on the density of the water within the piezometer, for groundwater, it is also called the Darcy slope, since it determines the quantity of a Darcy flux or discharge. It also has applications in open-channel flow where it can be used to determine whether a reach is gaining or losing energy. This requires a hydraulic head field, which can only be obtained from a numerical model. As with any other example in physics, energy must flow from high to low and this vector can be used in conjunction with Darcys law and a tensor of hydraulic conductivity to determine the flux of water in three dimensions
21.
Tunnel valley
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A tunnel valley can be as long as 100 km,4 km wide, and 400 m deep. Tunnel valleys were formed by erosion by water and served as subglacial drainage pathways carrying large volumes of melt water. Their cross-sections exhibit steep-sided flanks similar to fjord walls, and their bottoms are typical of subglacial glacial erosion. They presently appear as dry valleys, lakes, seabed depressions, if they are filled with sediment, their lower layers are filled primarily with glacial, glaciofluvial or glaciolacustrine sediment, supplemented by upper layers of temperate infill. They can be found in areas covered by glacial ice sheets including Africa, Asia, North America, Europe, Australia and offshore in the North Sea. Tunnel valleys appear in the literature under several terms, including tunnel channels, subglacial valleys, iceways, snake coils. The Upper Ordovician–Lower Silurian materials there contain a roughly 20 m thick, approximately 30% of the worlds oil is found in these shale deposits. The shale has been linked to glacial meltwater nutrient enrichment of the marine environment. Hence the presence of tunnel valleys is an indicator of the presence of oil in these areas, tunnel valleys represent a substantial fraction of all melt-water drainage from glaciers. Tunnel valleys are eroded into bedrock and filled with glacial debris of varying sizes. This configuration makes them excellent at capturing and storing water, hence they serve an important role as aquifers across much of Northern Europe, Canada and the United States. Examples include Oak Ridges Moraine Aquifer, Spokane Valley-Rathdrum Prairie Aquifer, Mahomet Aquifer, the Saginaw Lobe Aquifer, tunnel valleys have been observed as open valleys and as partially or totally buried valleys. If buried they may be partially or totally filled with glacial outwash or other debris, the valleys may be incised in bedrock, sand, silt, or clay. They vary in depth and width, Danish examples run from 0. 5–4 km wide. They have steep sides which are frequently asymmetric, tunnel valleys frequently include relatively straight individual segments parallel to and independent of one another. Tunnel valley courses may be interrupted, the interruption may include a stretch of elevated esker. The upstream portion – that section furthest into the glacier - consists of a branching system forming a network and they typically exhibit the largest cross-sectional area in the center of the course and terminate over a relatively short distance in elevated outwash fans at the ice-margin. Tunnel valleys are found to cross the regional gradient - as a result they may be crosscut by modern stream networks, in one example, tributaries of the Kalamazoo River cut at nearly right angles across buried tunnel channel filled with ice and debris
22.
Laurentide Ice Sheet
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Louis, Missouri—and then followed quite precisely the present course of the Missouri River up to the northern slopes of the Cypress Hills, beyond which it merged with the Cordilleran Ice Sheet. The ice coverage extended approximately as far south as 38 degrees latitude in the mid-continent and this ice sheet was the primary feature of the Pleistocene epoch in North America, commonly referred to as the ice age. It was up to 2 mi thick in Nunavik, Quebec, Canada and it created much of the surface geology of southern Canada and the northern United States, leaving behind glacially scoured valleys, moraines, eskers and glacial till. It also caused changes to the shape, size. Its cycles of growth and melting were an influence on global climate during its existence. This is because it served to divert the jet stream which would flow from the relatively warm Pacific Ocean through Montana. This interrupted the thermohaline circulation, creating the brief Younger Dryas cold epoch and a temporary re-advance of the ice sheet, some people have argued that huge influxes of fresh water stopped the feeding of the ice sheet and starved it, aiding the retreat that had already begun. During the Pre-Illinoian Stage the Laurentide Ice Sheet extended even farther south, advancing as far as the Missouri, the ultimate collapse of the Laurentide Ice Sheet is also suspected to have influenced European agriculture indirectly through the rise of global sea levels. Canadas oldest ice is a 20, 000-year-old remnant of the Laurentide Ice Sheet called the Barnes Ice Cap, canadian Shield Glacial history of Minnesota Lake Agassiz Wisconsin glaciation Noahs Flood Kick-started European Farming. The Retreat of Glaciers in North America
23.
Katla (volcano)
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Katla is a large volcano in southern Iceland. It is very active, twenty eruptions have been documented between 930 and 1918, at intervals of 13–95 years. It has not erupted violently for 99 years, although there may have small eruptions that did not break the ice cover, including ones in 1955,1999. Prior eruptions have had a Volcanic Explosivity Index of between 4 and 6 on a scale of 0 to 8, in comparison, the Eyjafjallajökull 2010 eruption had a VEI-4. The bigger VEI-6 eruptions are comparable to Mount Pinatubos 1991 eruption, Katla is one of the largest volcanoes in Iceland. It is situated to the north of Vík í Mýrdal and to the east of the smaller glacier Eyjafjallajökull and its peak reaches 1,512 metres and is partially covered by the Mýrdalsjökull glacier. The system has an area of 595 km2, the Eldgjá canyon is part of the same volcanic system. The caldera of the Katla volcano has a diameter of 10 km and is covered with 200–700 metres of ice, the volcano normally erupts every 40–80 years. The flood discharge at the peak of an eruption in 1755 has been estimated at 200, 000–400,000 m3/s, comparable to the average discharge of the Amazon, Mississippi, Nile. The name Katla derives from the word ketill, referring to the form of the volcano, Katla is also used as a female first name. Sixteen eruptions have been recorded for Katla since 930, the last major eruption started on 12 October 1918 and lasted for 24 days. It was likely a VEI-5 level eruption, the 1918 eruption resulted in extending the southern coast by 5 km due to laharic flood deposits. Its present dormancy is among the longest in known history, minor eruptions occurred in 2011,1999 and 1955. Major eruptions occurred in, Most of these resulted in glacial floods. The severe fissure eruption in 934 was one of the largest lava eruptions in the past 10,000 years, before the Hringvegur was constructed in 1974, people feared traversing the plains in front of the volcano because of the frequent jökulhlaup and the deep river crossings. Especially dangerous was the glacier outburst that followed the eruption of 1918, Katla has been showing signs of unrest since 1999, and geologists have concerns that it might erupt in the near future. Particularly, monitoring has been intensified following the March 2010 eruptions of a neighbouring volcano. The eruption of this nearby long-dormant volcano in March and April 2010 prompted fears among some geophysicists that it might trigger an eruption at the larger, in the past 1,000 years, all three known eruptions of Eyjafjallajökull have triggered subsequent Katla eruptions
24.
British Columbia
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British Columbia is the westernmost province of Canada, with a population of more than four million people located between the Pacific Ocean and the Rocky Mountains. British Columbia is also a component of the Pacific Northwest and the Cascadia bioregion, along with the U. S. states of Idaho, Oregon, Washington and Alaska. The first British settlement in the area was Fort Victoria, established in 1843, subsequently, on the mainland, the Colony of British Columbia was founded by Richard Clement Moody and the Royal Engineers, Columbia Detachment, in response to the Fraser Canyon Gold Rush. Port Moody is named after him, in 1866, Vancouver Island became part of the colony of British Columbia, and Victoria became the united colonys capital. In 1871, British Columbia became the province of Canada. Its Latin motto is Splendor sine occasu, the capital of British Columbia remains Victoria, the fifteenth-largest metropolitan region in Canada, named for the Queen who created the original European colonies. The largest city is Vancouver, the third-largest metropolitan area in Canada, the largest in Western Canada, in October 2013, British Columbia had an estimated population of 4,606,371. British Columbia evolved from British possessions that were established in what is now British Columbia by 1871, First Nations, the original inhabitants of the land, have a history of at least 10,000 years in the area. Today there are few treaties and the question of Aboriginal Title, notably, the Tsilhqotin Nation has established Aboriginal title to a portion of their territory, as a result of the recent Supreme Court of Canada decision. BCs economy is diverse, with service producing industries accounting for the largest portion of the provinces GDP and it is the endpoint of transcontinental railways, and the site of major Pacific ports that enable international trade. Though less than 5% of its vast 944,735 km2 land is arable and its climate encourages outdoor recreation and tourism, though its economic mainstay has long been resource extraction, principally logging, farming, and mining. Vancouver, the provinces largest city and metropolitan area, also serves as the headquarters of many western-based natural resource companies and it also benefits from a strong housing market and a per capita income well above the national average. The Northern Interior region has a climate with very cold winters. The climate of Vancouver is by far the mildest winter climate of the major Canadian cities, the provinces name was chosen by Queen Victoria, when the Colony of British Columbia, i. e. the Mainland, became a British colony in 1858. The current southern border of British Columbia was established by the 1846 Oregon Treaty, British Columbias land area is 944,735 square kilometres. British Columbias rugged coastline stretches for more than 27,000 kilometres and it is the only province in Canada that borders the Pacific Ocean. British Columbias capital is Victoria, located at the tip of Vancouver Island. Only a narrow strip of the Island, from Campbell River to Victoria, is significantly populated, much of the western part of Vancouver Island and the rest of the coast is covered by thick, tall and sometimes impenetrable temperate rainforest
25.
Coast Mountains
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The mountain ranges name derives from its proximity to the sea coast, and is often referred to as the Coast Range. The range includes volcanic and non-volcanic mountains and the ice fields of the Pacific and Boundary Ranges. The Coast Mountains are approximately 1,600 kilometres long and average 300 kilometres in width, covered in dense temperate rainforest on its western exposures, the range rises to heavily glaciated peaks, including the largest temperate-latitude ice fields in the world. On its eastern flanks, the tapers to the dry Interior Plateau. The Coast Mountains are part of the Pacific Ring of Fire—the ring of volcanoes, the Coast Mountains consists of three subdivisions known as the Pacific Ranges, the Kitimat Ranges, and the Boundary Ranges. The Pacific Ranges are the southernmost subdivision of the Coast Mountains, included in this subdivision is four of the five major coastal icecaps in the southern Coast Mountains. These are the largest temperate-latitude icecaps in the world and fuel a number of major rivers, other than logging and a large ski resort at the resort town of Whistler, most of the land in the range is completely undeveloped. Mount Waddington, the highest mountain of the Coast Mountains, lies in the Waddington Range of the Pacific Ranges, just north of the Pacific Ranges lies the central subdivision known as the Kitimat Ranges. This subdivision extends from the Bella Coola River and Burke Channel in the south to the Nass River in the north, the third and northernmost subdivision of the Coast Mountains is the Boundary Ranges, extending from the Nass River in the south to the Kelsall River in the north. This precipitation is among the heaviest in North America, the eastern slopes are relatively dry and less steep and protect the British Columbia Interior from the Pacific weather systems, resulting in dry warm summers and dry cold winters. Beyond the eastern slopes is a 154,635 km2 plateau occupying the southern, included within the Interior Plateau is a coalescing series of layered flood basalt lava flows. These sequences of fluid volcanic rock cover about 25,000 km2 of the Interior Plateau and have a volume of about 1,800 km3, the Coast Mountains consists of deformed igneous and metamorphosed structurally complex pre-Tertiary rocks. These originated in locations around the globe, the area is built of several different terranes of different ages with a broad range of tectonic origins. Further north the northwesterly structural trend of the Coast Mountains lies partly in a continental rift responsible for the creation of several volcanoes. These volcanoes form part of the Northern Cordilleran Volcanic Province, the most volcanically active area in Canada, the first event began 130 million years ago when a group of active volcanic islands approached a pre-existing continental margin and coastline of North America. This subduction zone eventually jammed and shut down completely 115 million years ago, ending the Omineca Arc, compression resulting from this collision crushed, fractured and folded rocks along the old continental margin. The Insular Belt then welded onto the continental margin by magma that eventually cooled to create a large mass of igneous rock. This large mass of rock is the largest granite outcropping in North America
26.
Chilko Lake
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Chilko Lake is a 180 km² lake in west-central British Columbia, at the head of the Chilko River on the Chilcotin Plateau. The lake is about 65 km long, with a southwest arm 10 km long and it is one of the largest lakes by volume in the province because of its great depth, and the largest above 1,000 m in elevation. It and Harrison Lake are the largest lakes in the southern Coast Mountains, Tatlayoko Lake, to the west across another range, is not part of the Chilcotin-Fraser drainage, however, but is part of the Homathko River drainage to Bute Inlet. The area spanning the head of Chilko Lake and Taseko Lake basins, Tsil. os is the Tsilhqotin name for Mount Tatlow 3,063 m, which stands in the ranges between Chilko and Taseko Lakes. In the 1950s, Chilko Lake and River were passed over as a potential resource for Alcan due to the salmon presence. The area between Tatlayoko and Chilko Lakes is not protected, however, and plans for the dams, one, the largest, would be built immediately atop the site of the first battle of the Chilcotin War, marked on government maps as Murderers Bar
27.
North America
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North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can also be considered a subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea. North America covers an area of about 24,709,000 square kilometers, about 16. 5% of the land area. North America is the third largest continent by area, following Asia and Africa, and the fourth by population after Asia, Africa, and Europe. In 2013, its population was estimated at nearly 565 million people in 23 independent states, or about 7. 5% of the worlds population, North America was reached by its first human populations during the last glacial period, via crossing the Bering land bridge. The so-called Paleo-Indian period is taken to have lasted until about 10,000 years ago, the Classic stage spans roughly the 6th to 13th centuries. The Pre-Columbian era ended with the migrations and the arrival of European settlers during the Age of Discovery. Present-day cultural and ethnic patterns reflect different kind of interactions between European colonists, indigenous peoples, African slaves and their descendants, European influences are strongest in the northern parts of the continent while indigenous and African influences are relatively stronger in the south. Because of the history of colonialism, most North Americans speak English, Spanish or French, the Americas are usually accepted as having been named after the Italian explorer Amerigo Vespucci by the German cartographers Martin Waldseemüller and Matthias Ringmann. Vespucci, who explored South America between 1497 and 1502, was the first European to suggest that the Americas were not the East Indies, but a different landmass previously unknown by Europeans. In 1507, Waldseemüller produced a map, in which he placed the word America on the continent of South America. He explained the rationale for the name in the accompanying book Cosmographiae Introductio, for Waldseemüller, no one should object to the naming of the land after its discoverer. He used the Latinized version of Vespuccis name, but in its feminine form America, following the examples of Europa, Asia and Africa. Later, other mapmakers extended the name America to the continent, In 1538. Some argue that the convention is to use the surname for naming discoveries except in the case of royalty, a minutely explored belief that has been advanced is that America was named for a Spanish sailor bearing the ancient Visigothic name of Amairick. Another is that the name is rooted in a Native American language, the term North America maintains various definitions in accordance with location and context. In Canadian English, North America may be used to refer to the United States, alternatively, usage sometimes includes Greenland and Mexico, as well as offshore islands
28.
Adirondack Mountains
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The Adirondack Mountains /ædᵻˈrɒndæk/ form a massif in the northeast of Upstate New York in the United States. Its boundaries correspond to the boundaries of Adirondack Park, the mountains form a roughly circular dome, about 160 miles in diameter and about 1 mile high. The current relief owes much to glaciation, the earliest written use of the name, spelled Rontaks, was in 1724 by the French missionary Joseph-François Lafitau. He defined it as tree eaters, in the Mohawk language, Adirondack means porcupine, an animal that may eat bark. The Mohawks had no written language at the time so Europeans have used various phonetic spellings, an English map from 1761 labels it simply Deer Hunting Country and the mountains were named Adirondacks in 1837 by Ebenezer Emmons. People first arrived in the following the settlement of the Americas around 10,000 BC. The Algonquian peoples and the Mohawk nation used the Adirondacks for hunting and travel, european colonisation of the area began with Samuel de Champlain visiting what is now Ticonderoga in 1609, and Jesuit missionary Isaac Jogues visited the region in 1642. In 1664 the land came under the control of the English when New Netherland was ceded to The Crown, after the American Revolutionary War, the lands passed to the people of New York State. Needing money to war debts, the new government sold nearly all the original public acreage about 7 million acres for pennies an acre. Lumbermen were welcomed to the interior, with few restraints, resulting in massive deforestation, for the history of the area since industrialization, see The History of Adirondack Park. In 1989, part of the Adirondack region was designated by UNESCO as the Champlain-Adirondack Biosphere Reserve, the rocks of the mountains originated about two billion years ago as 50,000 feet deep sediments at the bottom of a sea near the equator. Because of continental drift these collided with Laurentia in a mountain building episode known as the Grenville orogeny, during this time the sedimentary rock was changed into metamorphic rock. It is these Proterozoic minerals and lithologies that make up the core of the massif, such minerals of interest include, wollastonite, mined near Harrisville magnetite and hematite, formerly mined at the Benson Mines, Lyon Mountain, Mineville, Tawahus, and Witherbee. Graphite, mined near Hague and Ticonderoga, garnet, mined at the Barton Mine, north of Gore Mountain. Anorthosite, visible in road cuts on the New York State Route 3 between Saranac Lake and Tupper Lake, marble zinc, The Balmat-Edwards district on the northwest flank of the massif also in St. Lawrence County was a major zinc ore deposit titanium was mined at Tawahus. Around 600 million years ago the area began to be pulled apart, as Laurentia drifted away from Baltica, faults developed, running north to north east which formed valleys and deep lakes. Examples visible today include the grabens Lake George and Schroon Lake, by this time the Grenville mountains had been eroded away and the area was covered by a shallow sea. Several thousand feet of sediment accumulated on the sea bed, trilobites were the principal life-form of the sea bed, and fossil tracks can be seen in the Potsdam sandstone floor of the Paul Smiths Visitor Interpretive Center
29.
St. Lawrence Lowlands
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The Great Lakes-St. Lawrence Lowland is a bowl-shaped area located near to the Great Lakes. The Great Lakes basin area became a lake after the ice sheet melted. However, due to the presence of a deep faultline, all of water was eventually siphoned into the ocean. Thus, the primary defining historic feature of the lowlands the presence of deep soils within the watershed, the lowlands are split into these sub-regions by intrusions from adjacent physiographic regions. The next notable pinching occurs at Quebec City, where again the Shield meets the shore, anticosti and Newfoundland, both being islands, are separated by stretches of open salt water. There are animals such as warblers, wolves, snowshoe hares, blue birds, white-tailed deer, red-winged black birds, coyotes, frogs, eagles, and beavers. Even though the St. Lawrence Lowlands is the smallest landform region in Canada, it has a dense population, the Lowlands are abundant with agriculture, commerce, recreation locations, and transportation hubs. The St. Lawrence Lowlands is the most heavily industrialized landform in Canada and it is 70% of Canadas manufacturing systems and also 70% farm land. The soil is good for agricultural uses. It has the most fertile top soil in Canada
30.
Glacial Lake Iroquois
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Glacial Lake Iroquois was a prehistoric proglacial lake that existed at the end of the last ice age approximately 13,000 years ago. The lake was essentially an enlargement of the present Lake Ontario that formed because the St. Lawrence River downstream from the lake was blocked by the ice sheet near the present Thousand Islands, the level of the lake was approximately 30 m above the present level of Lake Ontario. The lake drained to the southeast, through a channel passing near present day Rome, the Rome Sand Plains has several sand ridges that geologists think were formed at this time. The channel then followed the valley of the Mohawk River to the Hudson River, the subsequent melting of the ice dam resulted in a sudden lowering of the lake to its present level, a potential trigger for the Younger Dryas episode. Two ancient shorelines in the Toronto area mark the existence of former glacial lakes, about 2 km inland from the shore a ridge known as the Iroquois Shoreline can be discerned. The old shoreline runs west-east running roughly parallel to Davenport Road just south of St. Clair Avenue West, further east, the Scarborough Bluffs also formed part of the shoreline of the ancient lake. Another ancient shoreline exists between 2–4 km offshore of Toronto and it is known as the Toronto Scarp and formed the shore of Glacial Lake Warren or Admiralty Lake. From Bluffers Park in Scarborough to just west of Hanlans Point is an underwater bluff, in New York, Ridge Road and New York State Route 104 run from west to east along a ridge of the old shoreline of Lake Iroquois. List of prehistoric lakes History of Lake Iroquois Lake Iroquois and its shore cliff, showing map of the lake Deglaciation of the Central St. Lawrence Lowland
31.
Hudson Valley
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The Hudson Valley comprises the valley of the Hudson River and its adjacent communities in the U. S. state of New York, from the cities of Albany and Troy southward to Yonkers in Westchester County. In the Hudson Highlands, the river enters a cut during previous ice ages. To the west lie the extensive Appalachian highlands, in the Tappan Zee region, the west side of the river has high cliffs produced by an erosion-resistant diabase, these cliffs range from 400–800 feet in height. The Hudson Valley is one section of the larger Ridge-and-Valley province. The northern portions of the Hudson Valley fall within the Eastern Great Lakes, during the last ice age, the valley was filled by a large glacier that pushed south as far as Long Island. Near the end of the last ice age, the Great Lakes drained south down the Hudson River, Lake Ontario is the remnant of that Lake. Large sand deposits remain from where Lake Iroquois drained into the Hudson, the first Dutch settlement was in the 1610s with the establishment of Fort Nassau, a trading post south of modern-day Albany, with the purpose of exchanging European goods for beaver pelts. Fort Nassau was later replaced by Fort Orange, during the French and Indian War in the 1750s, the northern end of the valley became the bulwark of the British defense against French invasion from Canada via Lake Champlain. The valley became one of the regions of conflict during the American Revolution. Part of the strategy of the British was to sever the colonies in two by maintaining control of the river. In 1797, the capital of New York was established permanently at Albany. Following the building of the Erie Canal, the became an important industrial center. The canal opened the Hudson Valley and New York City to commerce with the Midwest, however, in the mid 20th century, many of the industrial towns went into decline. The area is associated with the Hudson River School, a group of American Romantic painters who worked from about 1830 to 1870, a similar 30-mile stretch of the east bank in Dutchess and Columbia counties has been designated a National Historic Landmark. Tourism became an industry as early as 1810, as elite visitors frequented the mineral water at Ballston Spa. With convenient steamboat connections in New York City, and numerous hotels in romantic settings. Early guidebooks providing suggestions on their itinerary, middle-class people who read James Fenimore Coopers novels, or saw the paintings of the Hudson River School, were especially attracted. Hudson Valley Tech Valley is a name for the eastern part of New York State, including the Hudson Valley
32.
Glacial erratic
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A glacial erratic is a piece of rock that differs from the size and type of rock native to the area in which it rests. Erratics take their name from the Latin word errare, and are carried by glacial ice, Erratics can range in size from pebbles to large boulders such as Big Rock in Alberta. Geologists identify erratics by studying the surrounding the position of the erratic. Erratics are significant because, They can be transported by glaciers and their lithographic origin can be traced to the parent bedrock, allowing for confirmation of the ice flow route. They can be transported by ice rafting and this allows quantification of the extent of glacial flooding resulting from ice dam failure which release the waters stored in proglacial lakes such as Lake Missoula. Erratics released by ice-rafts that were stranded and subsequently melt, dropping their load, Erratics dropped by icebergs melting in the ocean can be used to track Antarctic and Arctic-region glacial movements for periods prior to record retention. Also known as dropstones, these can be correlated with ocean temperatures and levels to better understand, and examination of their mineralogical character leads the identification of their sources…. In geology, an erratic is material moved by forces from one location to another. Erratics are formed by ice erosion resulting from the movement of ice. Glaciers erode by multiple processes, abrasion/scouring, plucking, ice thrusting, glaciers crack pieces of bedrock off in the process of plucking, producing the larger erratics. In an abrasion process, debris in the basal ice scrapes along the bed, polishing and gouging the underlying rocks, similar to sandpaper on wood, producing smaller glacial till. In ice thrusting, the glacier freezes to its bed, then as it surges forward, evidence supports another option for creation of erratics as well, rock avalanches onto the upper surface of the glacier. Rock avalanche–supraglacial transport occurs when the glacier undercuts a rock face, the characteristics of rock avalanche–supraglacial transport includes, Monolithologic composition - a cluster of boulders of similar composition are frequently found in close proximity. Commingling of the multiple lithologies normally present throughout the basin, has not occurred. Angularity - the supraglacially transported rocks tend to be rough and irregular, the sides of boulders are roughly planar, suggesting that some surfaces may be original fracture planes. Great size - the size distribution of the boulders tends to be skewed toward larger boulders than those produced subglacially, surficial positioning of the boulders - the boulders are positioned on the surface of glacial deposits, as opposed to partially or totally buried. Orientations - the boulders may be enough that original fracture planes can be matched. Locations of the boulder trains - the boulders appear in rows, Erratic materials may be transported by multiple glacier flows prior to their deposition, which can complicate the reconstruction of the glacial flow
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Saint Lawrence River
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The Saint Lawrence River is a large river in the middle latitudes of North America. The Saint Lawrence River flows in a roughly north-easterly direction, connecting the Great Lakes with the Atlantic Ocean and forming the primary drainage outflow of the Great Lakes Basin. It traverses the Canadian provinces of Quebec and Ontario, and is part of the boundary between Ontario, Canada, and the U. S. state of New York. This river also provides the basis of the commercial Saint Lawrence Seaway, the estuary begins at the eastern tip of Île dOrléans, just downstream from Quebec City. The river becomes tidal around Quebec City, the St. Lawrence River runs 3,058 kilometres from the farthest headwater to the mouth and 1,197 km from the outflow of Lake Ontario. The farthest headwater is the North River in the Mesabi Range at Hibbing, the average discharge below the Saguenay River is 16,800 cubic metres per second. At Quebec City, it is 12,101 m3/s, the average discharge at the rivers source, the outflow of Lake Ontario, is 7,410 m3/s. The St. Lawrence River includes Lake Saint-Louis south of Montreal, Lake Saint Francis at Salaberry-de-Valleyfield, pierre Archipelago and the smaller Mingan Archipelago. Other islands include Île dOrléans near Quebec City and Anticosti Island north of the Gaspé and it is the second longest river in Canada. Lake Champlain and the Ottawa, Richelieu, Saguenay, and Saint-François rivers drain into the St. Lawrence. The St. Lawrence River is in an active zone where fault reactivation is believed to occur along late Proterozoic to early Paleozoic normal faults related to the opening of Iapetus Ocean. The faults in the area are related and are called the Saint Lawrence rift system. According to the United States Geological Survey, the St. Lawrence Valley is a province of the larger Appalachian division, containing the Champlain. However, in Canada, where most of the valley is, it is considered part of a distinct Saint Lawrence Lowlands physiographic division. Lawrence River itself was Jacques Cartier, at that time, the land along the river was inhabited by the St. Lawrence Iroquoians, at the time of Cartiers second voyage in 1535. Because Cartier arrived in the estuary on St. Lawrences feast day, the St. Lawrence River is partly within the U. S. and as such is that countrys sixth oldest surviving European place-name. The earliest regular Europeans in the area were the Basques, who came to the St Lawrence Gulf, the Basque whalers and fishermen traded with indigenous Americans and set up settlements, leaving vestiges all over the coast of eastern Canada and deep into the Saint Lawrence River. Basque commercial and fishing activity reached its peak before the Armada Invencibles disaster, initially, the whaling galleons from Labourd were not affected by the Spanish defeat
34.
Atlantic Ocean
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The Atlantic Ocean is the second largest of the worlds oceans with a total area of about 106,460,000 square kilometres. It covers approximately 20 percent of the Earths surface and about 29 percent of its surface area. It separates the Old World from the New World, the Atlantic Ocean occupies an elongated, S-shaped basin extending longitudinally between Eurasia and Africa to the east, and the Americas to the west. The Equatorial Counter Current subdivides it into the North Atlantic Ocean, in contrast, the term Atlantic originally referred specifically to the Atlas Mountains in Morocco and the sea off the Strait of Gibraltar and the North African coast. The Greek word thalassa has been reused by scientists for the huge Panthalassa ocean that surrounded the supercontinent Pangaea hundreds of years ago. The term Aethiopian Ocean, derived from Ancient Ethiopia, was applied to the Southern Atlantic as late as the mid-19th century, many Irish or British people refer to the United States and Canada as across the pond, and vice versa. The Black Atlantic refers to the role of ocean in shaping black peoples history. Irish migration to the US is meant when the term The Green Atlantic is used, the term Red Atlantic has been used in reference to the Marxian concept of an Atlantic working class, as well as to the Atlantic experience of indigenous Americans. Correspondingly, the extent and number of oceans and seas varies, the Atlantic Ocean is bounded on the west by North and South America. It connects to the Arctic Ocean through the Denmark Strait, Greenland Sea, Norwegian Sea, to the east, the boundaries of the ocean proper are Europe, the Strait of Gibraltar and Africa. In the southeast, the Atlantic merges into the Indian Ocean, the 20° East meridian, running south from Cape Agulhas to Antarctica defines its border. In the 1953 definition it extends south to Antarctica, while in later maps it is bounded at the 60° parallel by the Southern Ocean, the Atlantic has irregular coasts indented by numerous bays, gulfs, and seas. Including these marginal seas the coast line of the Atlantic measures 111,866 km compared to 135,663 km for the Pacific. Including its marginal seas, the Atlantic covers an area of 106,460,000 km2 or 23. 5% of the ocean and has a volume of 310,410,900 km3 or 23. 3%. Excluding its marginal seas, the Atlantic covers 81,760,000 km2 and has a volume of 305,811,900 km3, the North Atlantic covers 41,490,000 km2 and the South Atlantic 40,270,000 km2. The average depth is 3,646 m and the maximum depth, the bathymetry of the Atlantic is dominated by a submarine mountain range called the Mid-Atlantic Ridge. It runs from 87°N or 300 km south of the North Pole to the subantarctic Bouvet Island at 42°S, the MAR divides the Atlantic longitudinally into two halves, in each of which a series of basins are delimited by secondary, transverse ridges. The MAR reaches above 2000 m along most of its length, the MAR is a barrier for bottom water, but at these two transform faults deep water currents can pass from one side to the other
35.
Champlain Sea
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The Champlain Sea was a temporary inlet of the Atlantic Ocean, created by the retreating glaciers during the close of the last ice age. The Sea once included lands in what are now the Canadian provinces of Quebec and Ontario, as well as parts of the American states of New York, the mass of ice from the continental ice sheets had depressed the rock beneath it over millennia. As the land rose again, in the process known as isostatic rebound. The sea lasted from about 13,000 years ago to about 10,000 years ago and was continuously shrinking during that time, since the rebounding continent was slowly rising above sea level. At its peak, the sea extended inland as far south as Lake Champlain and somewhat farther west than the city of Ottawa, Ontario, the remaining glaciers fed the sea during that time, making it more brackish than typical seawater. It is estimated that the sea was as much as 150 metres above the level of todays Saint Lawrence, the best evidence of this former sea is the vast clay plain deposited along the Ottawa and St. Lawrence Rivers. This resulted in distinctive forest types, and large wetlands, other modern evidence of the sea can be seen in the form of whale fossils, and marine shells that have been found near the cities of Ottawa, Ontario, and Montreal, Quebec. There are also fossils of fish such as capelin. The Sea also left ancient raised shorelines in the coastal regions. The northern shore of the lake was in southern Quebec where outcrops of the Canadian shield form the Eardley Escarpment and this escarpment still has distinctive plants that may date back to the sea. The Late Quaternary Development of the Champlain Sea Basin, geological Association of Canada, Special Paper 36
36.
Thermohaline circulation
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Thermohaline circulation is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content, wind-driven surface currents travel polewards from the equatorial Atlantic Ocean, cooling en route, and eventually sinking at high latitudes. This dense water then flows into the ocean basins, while the bulk of it upwells in the Southern Ocean, the oldest waters upwell in the North Pacific. Extensive mixing therefore takes place between the basins, reducing differences between them and making the Earths oceans a global system. On their journey, the water masses transport both energy and matter around the globe, as such, the state of the circulation has a large impact on the climate of the Earth. The thermohaline circulation is called the ocean conveyor belt, the great ocean conveyor, or the global conveyor belt. On occasion, it is used to refer to the overturning circulation. Moreover, temperature and salinity gradients can lead to circulation effects that are not included in the MOC itself. The movement of surface currents pushed by the wind is fairly intuitive, for example, the wind easily produces ripples on the surface of a pond. Thus the deep ocean—devoid of wind—was assumed to be perfectly static by early oceanographers, however, modern instrumentation shows that current velocities in deep water masses can be significant. In general ocean water velocities range from fractions of centimeters per second to more than 1 m/s in surface currents like the Gulf Stream. In the deep ocean, the predominant driving force is differences in density, caused by salinity, there is often confusion over the components of the circulation that are wind and density driven. Note that ocean currents due to tides are also significant in places, most prominent in relatively shallow coastal areas. There they are thought to facilitate mixing processes, especially diapycnal mixing. The density of water is not globally homogeneous, but varies significantly and discretely. Sharply defined boundaries exist between water masses which form at the surface, and subsequently maintain their own identity within the ocean, but these sharp boundaries are not to be imagined spatially but rather in a T-S-diagram where water masses are distinguished. They position themselves above or below each other according to their density, warm seawater expands and is thus less dense than cooler seawater. Saltier water is denser than water because the dissolved salts fill interstices between water molecules, resulting in more mass per unit volume
37.
Columbia River Gorge
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The Columbia River Gorge is a canyon of the Columbia River in the Pacific Northwest of the United States. The gorge holds federally protected status as a National Scenic Area called the Columbia Gorge National Scenic Area and is managed by the Columbia River Gorge Commission, the gorge is a popular recreational destination. Each river has created a gorge through the Cascade Mountain Range, the Columbia River Gorge marks the state line between Oregon and Washington. The wide range of elevation and precipitation makes the Columbia River Gorge an extremely diverse, isolated micro-habitats have allowed for many species of endemic plants and animals to prosper, including at least 13 endemic wildflowers. The Gorge transitions between temperate rainforest to dry grasslands in only 80 miles, hosting a dramatic change in scenery while driving down I-84, in the western, temperate rainforest areas, forests are marked by bigleaf maples, Douglas Fir, and Western hemlock, all covered in epiphytes. In the transition zone, vegetation turns to Oregon white oak, Ponderosa pine, at the eastern end, the forests make way for expansive grasslands, with occasional pockets of lodgepole pine and Ponderosa pine. It also creates the conditions for snow and ice storms during the winter months which also draws very cold east winds at the mouth of the gorge on the west end. The Gorge is a destination for hiking, biking, sight-seeing, fishing. The area is known for its concentration of waterfalls, with over 90 on the Oregon side of the Gorge alone. Many are along the Historic Columbia River Highway, including the notable 620-foot -high Multnomah Falls, trails and day use sites are maintained by the Forest Service and many Oregon and Washington state parks. The Columbia River Gorge began forming as far back as the Miocene, during this period the Cascades Range was forming, which slowly moved the Columbia Rivers delta about 100 miles north to its current location. This quick erosion left many layers of rock exposed. The gorge has supported human habitation for over 13,000 years, evidence of the Folsom and Marmes people, who crossed the Bering land bridge from Asia, were found in archaeological digs. Excavations near Celilo Falls, a few miles east of The Dalles, the gorge has provided a transportation corridor for thousands of years. Native Americans would travel through the Gorge to trade at Celilo Falls, in 1805, the route was used by the Lewis and Clark Expedition to reach the Pacific. Early European and American settlers subsequently established steamboat lines and railroads through the gorge, today, the BNSF Railway runs freights along the Washington side of the river, while its rival, the Union Pacific Railroad, runs freights along the Oregon shore. Until 1997, Amtraks Pioneer also used the Union Pacific tracks, the Portland segment of the Empire Builder uses the BNSF tracks that pass through the gorge. The Columbia River Highway, built in the early 20th century, was the first major paved highway in the Pacific Northwest
38.
Missoula Floods
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The Missoula Floods refer to the cataclysmic floods that swept periodically across eastern Washington and down the Columbia River Gorge at the end of the last ice age. The glacial flood events have been researched since the 1920s and these glacial lake outburst floods were the result of periodic sudden ruptures of the ice dam on the Clark Fork River that created Glacial Lake Missoula. After each ice dam rupture, the waters of the lake would rush down the Clark Fork and the Columbia River, flooding much of eastern Washington, after the rupture, the ice would reform, creating Glacial Lake Missoula again. Alternate estimates for the flow rate of the largest flood include 17 cubic kilometers per hour. The maximum flow speed approached 36 meters/second.5 million years ago, Geologist J Harlen Bretz first recognized evidence of the catastrophic floods, which he called the Spokane Floods, in the 1920s. He was researching the Channeled Scablands in Eastern Washington, the Columbia Gorge, in the summer of 1922, and for the next seven years, Bretz conducted field research of the Columbia River Plateau. He had been interested in unusual erosion features in the area since 1910 after seeing a newly published topographic map of the Potholes Cataract, Bretz coined the term Channeled Scablands in 1923 to refer to the area near the Grand Coulee, where massive erosion had cut through basalt deposits. Bretz published a paper in 1923, arguing that the channeled scablands in Eastern Washington were caused by flooding in the distant past. Bretzs view, which was seen as arguing for an explanation of the geology, ran against the prevailing view of uniformitarianism. Another geologist at the meeting, J. T. Pardee, had worked with Bretz and had evidence of an ancient glacial lake that lent credence to Bretzs theories, Bretz defended his theories, and this kicked off an acrimonious 40-year debate over the origin of the Scablands. After Pardee studied the canyon of the Flathead River, he estimated that flood waters in excess of 45 miles per hour would be required to roll the largest of the boulders moved by the flood. He estimated the flow was nine cubic miles per hour. Estimates place the flow at ten times the flow of all current rivers combined, the Missoula Floods have also been referred to as the Bretz Floods in honor of Bretz. As the depth of the water in Lake Missoula increased, the pressure at the bottom of the ice dam increased enough to lower the point of water below the temperature of the ice forming the dam. This allowed liquid water to seep into minuscule cracks present in the ice dam, over a period of time, the friction from water flowing through these cracks generated enough heat to melt the ice walls and enlarge the cracks. This allowed more water to flow through the cracks, generating more heat and this feedback cycle eventually weakened the ice dam so much that it could no longer support the pressure of the water behind it, and it failed catastrophically. This process is known as a lake outburst flood. As the water emerged from the Columbia River gorge, it backed up again at the 1 mile wide narrows near Kalama, some temporary lakes rose to an elevation of more than 400 ft, flooding the Willamette Valley to Eugene, Oregon and beyond
39.
Altai flood
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The Altai flood refers to the cataclysmic flood that according to some geomorphologists swept along the Katun River in the Altai Republic at the end of the last ice age. These glacial lake outburst floods were the result of periodic sudden ruptures of ice dams like those triggering the Missoula flood, large glacial outburst floods have been researched since the 1920s in USA only. The largest of these lakes had a volume of hundreds of cubic kilometers. Giant current ripples of up to 18 meters high and 225 meters per wavelength were created at several places on the lake bottom. They are best developed just east of the Tyetyo River in the part of the Kuray Basin. They are made up of rounded pebble gravel, Giant bars found along the lower Chuya River and the Katun River as much as 300 m above modern river levels, with lengths up to five kilometers. These bars diminish in height and thickness downstream to about 60 m near Gorno-Altaisk, some of these bars form lakes when blocking small tributaries of the Katun. Much of the gravel deposited along the Katun valley lacks a stratigraphic structure, unique block deposits cap erosional terraces that are a few kilometers long, tens of meters wide, and about 4 m above the lower bars. Block sizes range up to 20 m on the long axis, cuspate erosional hollows and accumulation ridges are associated with individual blocks. Rudoy estimates the discharge required to transport these blocks in suspension was about 1 million cms, ice-rafted boulders up to several meters in diameter. Eddy deposits are seen along the Katun River between Inya and Mali Yaloman, dating of the gravel bars has yielded at least 3 times of deposition, suggesting that multiple floods occurred. As the lake grew larger and deeper, the ice dam eventually failed and this flood may have been the greatest discharge of freshwater on Earth, since its magnitude has been estimated similar to that of the Missoula flood in North America. The age of catastrophic flooding is not tightly constrained, and may involve several events, the mechanisms of lake filling and ice dam failure would suggest an early or late glacial time, whereas conditions at glacial maxima would seem to preclude such events. The catastrophic flood occurred between 12000 BC and 9000 BC, most of the water discharge is thought to have occurred during one day, with peak discharges of 107 m3/s. The maximum lake volume was 6x1011 m3 with an area of 1. 5x109 m2, the ice dam was about 650 m high. From there the waters may have followed through the Uzboy spillway into the Caspian Sea, then through the Maryinsky spillway into the Black Sea. Diluvium Giant current ripples Missoula flood Outburst flood Lee,2004, in Russian, Eng. summary, pp. 134-211 pp
40.
Diluvium
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The term was formerly given to the boulder clay deposits, supposed to have been caused by the Noachian deluge. The term diluvium in the meaning of A. N. Rudoy has become accepted, nearly all intermountain depressions in southern Siberia and northern Mongolia hosted glacier-dammed lakes during the Pleistocene ice ages. Climatic changes and hydrostatic alterations of the ice dams were followed by repeated fillings, the lake outbursts had a cataclysmic character. In accordance with conditions, the glaciers would protrude again into the main drainage valleys immediately after dam deformations and lake outbursts. The greatest of the lakes achieved volumes up to hundreds of cubic kilometres and these floods transformed the drainage valleys, repeatedly building new sediment deposits. The dating of the latter proves the occurrence of floods in the Chuya. During that period there were at least five large-scale flooding events, enormous water masses were drained simultaneously and repeatedly toward the south of West Siberia. The total water volume out of the Altai basins only used to reach 10 thousand cubic kilometres, with some periodicity, all of the basins of South Siberia were able to deliver northwards about 60 thousand cubic kilometres of flood waters. Alluvium Altai flood Channeled Scablands Colluvium Eluvium Giant current ripples Illuvium Chuya Flood Video Rudoy, glacier-dammed lakes and geological work of glacial superfloods in the Late Pleistocene, Southern Siberia, Altai Mountains, Quaternary International,2002, Vol. 87/1, pp. 119-140. Ice-dammed lakes and glacial debris super-flows in the Altay and the Sayan Mountains in late Wurm, Новые результаты моделирования гидравлических характеристик дилювиальных потоков из позднечетвертичного Чуйско-Курайского ледниково-подпрудного озера. Diluvium Video Athabasca-video in large Scale Alexei Rudoy, Giant gravel bars - дилювиально-аккумулятивные валы. Glacial Lakes and Glacial Lake Outburst Floods in Nepal, - International Centre for Integrated Mountain Development, Kathmandu, March 2011
41.
Giant current ripples
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Giant current ripples are active channel topographic forms up to 20 m high, which develop within near-talweg areas of the main outflow valleys created by glacial lake outburst floods. Giant current ripple marks are morphologic and genetic macroanalogues of small current ripples formed in sandy stream sediments, the giant current ripple marks are important depositional forms in diluvial plain and mountain scablands. J. Pardee gave brief characteristics to the forms found by him already in the early 20th century while researching the Late Pleistocene lake Missoula, J. Pardee was a member of this organization. Thus, it is this name that we should associate with the discovery. After Pardees publication in 1942, giant current ripples have been found everywhere on the territory of the basaltic Columbia Plateau. A special study of the geomorphology and palaeohydrology of the American scabland was begun by Victor Baker, some other so far known means had certainly been used for the purpose as well since Bretzs times, in particular, the functional dependences by Schezi and Manning. However, those dependences estimated velocities and discharges of the floods at the line. For nearly sixty years the well-known ice-dammed Lake Missoula and its cataclysmic outbursts was considered as a one in the worlds scientific literature. Special tourist routes were organised at most impressive sites of giant vessels, canyons-coulees, vast fields of giant current ripples, here professional guides tell the tourists about hydrospheric catastrophes which took place in the ice ages in America. A. Carling flood deposit sedimentology is becoming more and more notable, in Russia nobody had known anything about the regime of ice-dammed lakes until the 1980s and, of course, had not looked for any traces of their failures, either. As a matter of fact, this question was considered rhetorical, since there are strandlines on the sides of the depressions, moreover, in some authors opinions, the lakes appeared in the depressions, in particular in the Altai, only once, at the most – twice. And when such lake terraces could be distinguished, if any at all, in the depressions, then the question of the lakes did not arise. Nevertheless, in the late 1950s G. F. Lungershausen, the genetic diagnostics of the giant ripples in the Kuray Basin had a general character and was essentially limited to the terminologically correct definition only. The article explained the origin of the direction of the water torrents proper by some neotectonic reasons, Rakovets about the diluvial origin of giant ripple marks in Kuray was denied by E. V. Deviatkin, who referred to a conclusion made by E. V. Shantser and wrote that the ripple marks in Kuray Basin were results of heavy erosional processing of a huge fluvioglacial fan. Petkevich expressed an opinion in her candidate thesis. She believed that the relief on the right bank of the Tetio River in Kuray Basin was a washed proluvial fan
42.
Lake Ojibway
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Lake Ojibway was a prehistoric lake in what is now northern Ontario and Quebec in Canada. Ojibway was the last of the proglacial lakes of the last ice age. Comparable in size to Lake Agassiz, and north of the Great Lakes, the former lakebed forms the modern Clay Belt, an area of fertile land. The lake drained in what must have been a catastrophic and dramatic manner around 8,200 years BP, one hypothesis is that a weakening ice dam separating it from Hudson Bay broke, as the lake was roughly 250 m above sea level. A comparable mechanism produced the Missoula floods that created the channeled scablands of the Columbia River basin. A recent analysis states it has not been determined whether the lake drained by a breach of the ice dam, by water spilling over the glacier. It is also not conclusively known whether there were one or more pulses, the draining of Lake Ojibway is a possible cause of the 8.2 kiloyear event, a major global cooling that occurred 8,200 years BP. Tyrrell Sea Glacial lake outburst flood Lake Agassiz Glacial Lake Missoula List of prehistoric lakes Deluge How it happened, The catastrophic flood that cooled the Earth
