A river delta is a triangular landform created by the deposition of the sediments that are carried by the waters of a river , where the river merges with a body of slow-moving water or with a body of stagnant water. The creation of a river delta occurs at the river mouth , where the river merges into an ocean , a sea , or an estuary , into a lake , a reservoir , or (more rarely) into another river that cannot carry away the sediment supplied by the feeding river. Etymologically, the term river delta derives from the triangular shape (Δ) of the uppercase Greek letter delta . In hydrology , the dimensions of a river delta are determined by the balance between the watershed processes that supply sediment and the watershed processes that redistribute, sequester, and export the supplied sediment into the receiving basin.
123-397: River deltas are important in human civilization , as they are major agricultural production centers and population centers. They can provide coastline defence and can impact drinking water supply. They are also ecologically important, with different species' assemblages depending on their landscape position. On geologic timescales , they are also important carbon sinks . A river delta
246-404: A philosophy that assumed there were innate differences between "civilized" and "uncivilized" peoples. "Civilization" can also refer to the culture of a complex society, not just the society itself. Every society, civilization or not, has a specific set of ideas and customs, and a certain set of manufactures and arts that make it unique. Civilizations tend to develop intricate cultures, including
369-636: A state -based decision-making apparatus, a literature , professional art , architecture , organized religion and complex customs of education , coercion and control associated with maintaining the elite. The intricate culture associated with civilization has a tendency to spread to and influence other cultures, sometimes assimilating them into the civilization, a classic example being Chinese civilization and its influence on nearby civilizations such as Korea , Japan and Vietnam Many civilizations are actually large cultural spheres containing many nations and regions. The civilization in which someone lives
492-472: A "civilized" way of living. In the 19th century, the idea of European culture as "civilized" and superior to "uncivilized" non-European cultures was fully developed, and civilization became a core part of European identity. The idea of civilization can also be used as a justification for dominating another culture and dispossessing a people of their land. For example, in Australia , British settlers justified
615-450: A characteristic of early civilizations. This " urban revolution "—a term introduced by Childe in the 1930s—from the 4th millennium BCE, marked the beginning of the accumulation of transferable economic surpluses , which helped economies and cities develop. Urban revolutions were associated with the state monopoly of violence , the appearance of a warrior , or soldier, class and endemic warfare (a state of continual or frequent warfare),
738-404: A civilization as a complex system , i.e., a framework by which a group of objects can be analysed that work in concert to produce some result. Civilizations can be seen as networks of cities that emerge from pre-urban cultures and are defined by the economic, political, military, diplomatic, social and cultural interactions among them. Any organization is a complex social system and a civilization
861-537: A civilization has often been understood as a larger and "more advanced" culture , in implied contrast to smaller, supposedly less advanced cultures. In this broad sense, a civilization contrasts with non-centralized tribal societies, including the cultures of nomadic pastoralists , Neolithic societies, or hunter-gatherers ; however, sometimes it also contrasts with the cultures found within civilizations themselves. Civilizations are organized densely-populated settlements divided into hierarchical social classes with
984-493: A common location for civilizations to flourish due to access to flat land for farming, freshwater for sanitation and irrigation , and sea access for trade. Deltas often host extensive industrial and commercial activities, and agricultural land is frequently in conflict. Some of the world's largest regional economies are located on deltas such as the Pearl River Delta , Yangtze River Delta , European Low Countries and
1107-443: A complex recording system consisting of knotted strings of different lengths and colors: the " Quipus ", and still functioned as a civilized society. Aided by their division of labour and central government planning, civilizations have developed many other diverse cultural traits. These include organized religion , development in the arts, and countless new advances in science and technology. Assessments of what level of civilization
1230-470: A critical threshold where collapse is inevitable. Politically associated with over-reach, and as a result of the environmental exhaustion and polarization of wealth between rich and poor, he concludes the current system is fast arriving at a situation where continuation of the existing system saddled with huge deficits and a hollowed-out economy is physically, socially, economically and politically impossible. Although developed in much more depth, Berman's thesis
1353-544: A delta but enter into the sea in the form of an estuary . Notable examples include the Gulf of Saint Lawrence and the Tagus estuary. In rare cases, the river delta is located inside a large valley and is called an inverted river delta . Sometimes a river divides into multiple branches in an inland area, only to rejoin and continue to the sea. Such an area is called an inland delta , and often occurs on former lake beds. The term
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#17327733285291476-693: A division of labour and a more diverse range of human activity, a defining trait of civilizations. However, in some places hunter-gatherers have had access to food surpluses, such as among some of the indigenous peoples of the Pacific Northwest and perhaps during the Mesolithic Natufian culture . It is possible that food surpluses and relatively large scale social organization and division of labour predates plant and animal domestication. Civilizations have distinctly different settlement patterns from other societies. The word civilization
1599-533: A fan. The more often the flow changes course, the shape develops closer to an ideal fan because more rapid changes in channel position result in a more uniform deposition of sediment on the delta front. The Mississippi and Ural River deltas, with their bird's feet, are examples of rivers that do not avulse often enough to form a symmetrical fan shape. Alluvial fan deltas, as seen by their name, avulse frequently and more closely approximate an ideal fan shape. Most large river deltas discharge to intra-cratonic basins on
1722-429: A few main distributaries. Once a wave-dominated or river-dominated distributary silts up, it is abandoned, and a new channel forms elsewhere. In a tidal delta, new distributaries are formed during times when there is a lot of water around – such as floods or storm surges . These distributaries slowly silt up at a more or less constant rate until they fizzle out. A tidal freshwater delta is a sedimentary deposit formed at
1845-542: A flat arid area splits into channels that evaporate as it progresses into the desert. The Okavango Delta in Botswana is one example. See endorheic basin . The generic term mega delta can be used to describe very large Asian river deltas, such as the Yangtze , Pearl , Red , Mekong , Irrawaddy , Ganges-Brahmaputra , and Indus . The formation of a delta is complicated, multiple, and cross-cutting over time, but in
1968-431: A flat or gently ascending back, which are also called as “Gilbert-type” mouth bars, commonly in deep-water areas of the delta . Lateral spreading of turbulent jet enhanced by increasing frictional resistance in shallow inshore waters, also associated with high bed load, produces almost triangular “middle ground bar” in the mouth of the river causing the channel to bifurcate. As progradation continues, new bars develop at
2091-437: A mature delta with a distributary network. Another way these distributary networks form is from the deposition of mouth bars (mid-channel sand and/or gravel bars at the mouth of a river). When this mid-channel bar is deposited at the mouth of a river, the flow is routed around it. This results in additional deposition on the upstream end of the mouth bar, which splits the river into two distributary channels. A good example of
2214-695: A new approach was developed, especially in Germany, first by Johann Gottfried Herder and later by philosophers such as Kierkegaard and Nietzsche . This sees cultures as natural organisms, not defined by "conscious, rational, deliberative acts", but a kind of pre-rational "folk spirit". Civilization, in contrast, though more rational and more successful in material progress, is unnatural and leads to "vices of social life" such as guile, hypocrisy, envy and avarice. In World War II , Leo Strauss , having fled Germany, argued in New York that this opinion of civilization
2337-580: A polity has reached are based on comparisons of the relative importance of agricultural as opposed to trading or manufacturing capacities, the territorial extensions of its power, the complexity of its division of labour , and the carrying capacity of its urban centres . Secondary elements include a developed transportation system, writing, standardized measurement, currency, contractual and tort -based legal systems, art, architecture, mathematics, scientific understanding, metallurgy , political structures, and organized religion. The idea of civilization implies
2460-417: A progression or development from a previous "uncivilized" state. Traditionally, cultures that defined themselves as "civilized" often did so in contrast to other societies or human groupings viewed as less civilized, calling the latter barbarians , savages , and primitives . Indeed, the modern Western idea of civilization developed as a contrast to the indigenous cultures European settlers encountered during
2583-426: A river mouth bar basinward of the levee tips due to the decrease in jet momentum flux and resulting the high sedimentation rate in this region; (2) The subaqueous levees extend basinward and the river mouth bar aggrades and progrades since its presence causes flow acceleration on streamlines over the bar, and subsequently, this acceleration changes the sediment transport gradient over the bar triggering erosion on
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#17327733285292706-533: A ruling elite and subordinate urban and rural populations, which engage in intensive agriculture , mining , small-scale manufacture and trade . Civilization concentrates power, extending human control over the rest of nature, including over other human beings. The word civilization relates to the Latin civitas or ' city '. As the National Geographic Society has explained it: "This
2829-444: A simple delta three main types of bedding may be distinguished: the bottomset beds, foreset/frontset beds, and topset beds. This three-part structure may be seen on small scale by crossbedding . Human activities in both deltas and the river basins upstream of deltas can radically alter delta environments. Upstream land use change such as anti-erosion agricultural practices and hydrological engineering such as dam construction in
2952-455: A species of developed humanity is capable". This "unified culture" concept of civilization also influenced the theories of historian Arnold J. Toynbee in the mid-twentieth century. Toynbee explored civilization processes in his multi-volume A Study of History , which traced the rise and, in most cases, the decline of 21 civilizations and five "arrested civilizations". Civilizations generally declined and fell, according to Toynbee, because of
3075-507: A strategic location for the research projects regarding estuarine and delta restoration which makes them ideal for studying the effects of river sediment reduction and relative sea level rise and for estimating the evolution, including land loss and inundation, of the river deltas. A serious example is the Mississippi River Delta where coastal wetlands are disappearing at a rate of approximately 1% of land per year. On
3198-411: A surplus of food, particularly when people use intensive agricultural techniques such as artificial fertilization , irrigation and crop rotation . It is possible but more difficult to accumulate horticultural production, and so civilizations based on horticultural gardening have been very rare. Grain surpluses have been especially important because grain can be stored for a long time. Research from
3321-549: Is a good example of a fluvial-dominated delta whose outflow is buoyancy-dominated. Channel abandonment has been frequent, with seven distinct channels active over the last 5000 years. Other fluvial-dominated deltas include the Mackenzie delta and the Alta delta. A Gilbert delta (named after Grove Karl Gilbert ) is a type of fluvial-dominated delta formed from coarse sediments, as opposed to gently sloping muddy deltas such as that of
3444-513: Is a large organization. Systems theory helps guard against superficial and misleading analogies in the study and description of civilizations. Systems theorists look at many types of relations between cities, including economic relations, cultural exchanges and political/diplomatic/military relations. These spheres often occur on different scales. For example, trade networks were, until the nineteenth century, much larger than either cultural spheres or political spheres. Extensive trade routes, including
3567-758: Is a major sign that Mars once had large amounts of water. Deltas have been found over a wide geographical range. Below are pictures of a few. Civilization A civilization (also spelled civilisation in British English ) is any complex society characterized by the development of the state , social stratification , urbanization , and symbolic systems of communication beyond signed or spoken languages (namely, writing systems and graphic arts ). Civilizations include features such as agriculture , architecture , infrastructure , technological advancement , currency , taxation , regulation , and specialization of labour . Historically,
3690-436: Is believed by some archaeologists to be the oldest known town in present-day Europe. The 8.2 Kiloyear Arid Event and the 5.9 Kiloyear Inter-pluvial saw the drying out of semiarid regions and a major spread of deserts . This climate change shifted the cost-benefit ratio of endemic violence between communities, which saw the abandonment of unwalled village communities and the appearance of walled cities, seen by some as
3813-588: Is called by the Ionians ", including describing the outflow of silt into the sea and the convexly curved seaward side of the triangle. Despite making comparisons to other river systems deltas, Herodotus did not describe them as "deltas". The Greek historian Polybius likened the land between the Rhône and Isère rivers to the Nile Delta, referring to both as islands, but did not apply the word delta. According to
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3936-422: Is concerned with the study of artifact remains of non-human civilizations to reconstruct and interpret past lives of alien societies if such get discovered and confirmed scientifically. Mouth bars A mouth bar is an element of a deltaic system, which refers to the typically mid-channel deposition of the sediment transported by the river channel at the river mouth . River mouth bars form because
4059-562: Is extremely significant within the coastal landscape. Most of the time, they are subaqueous and inaccessible. However, after they emerge and their subaerial portion becomes visible, they evolve into deltaic islands. Consequently, by promoting land expansion, they restore artificially modified shorelines and mitigate coastal erosion , protect coastal communities, promote vegetation growth, provide habitat for rich and productive estuarine ecosystems, and potentially be utilized for farming, living and engineering. Moreover, mouth bar deposits offer
4182-410: Is similar in some ways to that of Urban Planner, Jane Jacobs who argues that the five pillars of United States culture are in serious decay: community and family; higher education; the effective practice of science; taxation and government; and the self-regulation of the learned professions. The corrosion of these pillars, Jacobs argues, is linked to societal ills such as environmental crisis, racism and
4305-547: Is so named because the shape of the Nile Delta approximates the triangular uppercase Greek letter delta . The triangular shape of the Nile Delta was known to audiences of classical Athenian drama ; the tragedy Prometheus Bound by Aeschylus refers to it as the "triangular Nilotic land", though not as a "delta". Herodotus 's description of Egypt in his Histories mentions the Delta fourteen times, as "the Delta, as it
4428-409: Is sometimes defined as "living in cities". Non-farmers tend to gather in cities to work and to trade. Compared with other societies, civilizations have a more complex political structure, namely the state . State societies are more stratified than other societies; there is a greater difference among the social classes. The ruling class , normally concentrated in the cities, has control over much of
4551-565: Is that person's broadest cultural identity. It is precisely the protection of this cultural identity that is becoming increasingly important nationally and internationally. According to international law, the United Nations and UNESCO try to set up and enforce relevant rules. The aim is to preserve the cultural heritage of humanity and also the cultural identity, especially in the case of war and armed conflict. According to Karl von Habsburg , President of Blue Shield International ,
4674-502: Is the key indicator in determining the extent of a civilization. David Wilkinson has proposed that economic and military-diplomatic integration of the Mesopotamian and Egyptian civilizations resulted in the creation of what he calls the "Central Civilization" around 1500 BCE. Central Civilization later expanded to include the entire Middle East and Europe, and then expanded to a global scale with European colonization, integrating
4797-566: Is why the most basic definition of the word civilization is 'a society made up of cities.'" The earliest emergence of civilizations is generally connected with the final stages of the Neolithic Revolution in West Asia , culminating in the relatively rapid process of urban revolution and state formation , a political development associated with the appearance of a governing elite. The English word civilization comes from
4920-579: The Journal of Political Economy contradicts the surplus model. It postulates that horticultural gardening was more productive than cereal farming. However, only cereal farming produced civilization because of the appropriability of yearly harvest. Rural populations that could only grow cereals could be taxed allowing for a taxing elite and urban development. This also had a negative effect on rural population, increasing relative agricultural output per farmer. Farming efficiency created food surplus and sustained
5043-659: The Greater Tokyo Area . The Ganges–Brahmaputra Delta , which spans most of Bangladesh and West Bengal and empties into the Bay of Bengal , is the world's largest delta. The Selenga River delta in the Russian republic of Buryatia is the largest delta emptying into a body of fresh water, in its case Lake Baikal . Researchers have found a number of examples of deltas that formed in Martian lakes . Finding deltas
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5166-824: The Neolithic and Mesolithic stage of the cultures of many of the peoples they encountered. Nonetheless, developments in the Neolithic stage, such as agriculture and sedentary settlement, were critical to the development of modern conceptions of civilization. The Natufian culture in the Levantine corridor provides the earliest case of a Neolithic Revolution, with the planting of cereal crops attested from c. 11,000 BCE. The earliest neolithic technology and lifestyle were established first in Western Asia (for example at Göbekli Tepe , from about 9,130 BCE), later in
5289-529: The Nile Delta and Colorado River Delta are some of the most extreme examples of the devastation caused to deltas by damming and diversion of water. Historical data documents show that during the Roman Empire and Little Ice Age (times when there was considerable anthropogenic pressure), there was significant sediment accumulation in deltas. The industrial revolution has only amplified the impact of humans on delta growth and retreat. Ancient deltas benefit
5412-573: The Royal Cemetery at Ur is suggested was traded northwards from Mozambique. Many theorists argue that the entire world has already become integrated into a single " world system ", a process known as globalization . Different civilizations and societies all over the globe are economically, politically, and even culturally interdependent in many ways. There is debate over when this integration began, and what sort of integration – cultural, technological, economic, political, or military-diplomatic –
5535-658: The Silk Road through Central Asia and Indian Ocean sea routes linking the Roman Empire , Persian Empire , India and China, were well established 2000 years ago when these civilizations scarcely shared any political, diplomatic, military, or cultural relations. The first evidence of such long-distance trade is in the ancient world . During the Uruk period , Guillermo Algaze has argued that trade relations connected Egypt, Mesopotamia, Iran and Afghanistan. Resin found later in
5658-567: The Yellow River and Yangtze basins in China (for example the Peiligang and Pengtoushan cultures), and from these cores spread across Eurasia. Mesopotamia is the site of the earliest civilizations developing from 7,400 years ago. This area has been evaluated by Beverley Milton-Edwards as having "inspired some of the most important developments in human history including the invention of
5781-428: The cross-sectional area of the expanding sediment-laden outflow increases, and consequently, the sediment transport rate down the jet centerline decreases basinward as flow progresses from confined to unconfined. More specifically, four stages of the river mouth bar formation are: (1) Turbulent jet, expanding into a shallow and sloping basin, first creates parallel subaqueous levees extending basinward and starting
5904-505: The geologic record . Analyses of the hydraulic and sedimentologic conditions of river mouth bar formation, progradation and aggradation , and prediction on their shape, size and spacing are incredibly valuable for reservoir prediction. Eventually, in estuarine regions, there is a mutual interaction between morphology and flow dynamics. While mouth bar morphology is shaped and affected by flow and sediment dynamics or wave and current patterns, mouth bars also modify those dynamics and change
6027-677: The silurian hypothesis , however, considers whether it would "be possible to detect an industrial civilization in the geological record" given the paucity of geological information about eras before the quaternary . Astronomers speculate about the existence of communicating with intelligent civilizations within and beyond the Milky Way galaxy, usually using variants of the Drake equation . They conduct searches for such intelligences – such as for technological traces, called " technosignatures ". The proposed proto-scientific field " xenoarchaeology "
6150-646: The "true clash of civilizations" between the Muslim world and the West is caused by the Muslim rejection of the West's more liberal sexual values, rather than a difference in political ideology, although they note that this lack of tolerance is likely to lead to an eventual rejection of (true) democracy. In Identity and Violence Sen questions if people should be divided along the lines of a supposed "civilization", defined by religion and culture only. He argues that this ignores
6273-581: The 1760s, again from French. The first known use in French is in 1757, by Victor de Riqueti, marquis de Mirabeau , and the first use in English is attributed to Adam Ferguson , who in his 1767 Essay on the History of Civil Society wrote, "Not only the individual advances from infancy to manhood but the species itself from rudeness to civilisation". The word was therefore opposed to barbarism or rudeness, in
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#17327733285296396-503: The 18th century, civilization was not always seen as an improvement. One historically important distinction between culture and civilization is from the writings of Rousseau , particularly his work about education, Emile . Here, civilization, being more rational and socially driven, is not fully in accord with human nature , and "human wholeness is achievable only through the recovery of or approximation to an original discursive or pre-rational natural unity" (see noble savage ). From this,
6519-460: The 19th century were taller than their "civilized" American and European counterparts. The average stature of a population is a good measurement of the adequacy of its access to necessities, especially food, and its freedom from disease. Writing , developed first by people in Sumer , is considered a hallmark of civilization and "appears to accompany the rise of complex administrative bureaucracies or
6642-656: The Americas, Australia, China and Japan by the nineteenth century. According to Wilkinson, civilizations can be culturally heterogeneous, like the Central Civilization, or homogeneous, like the Japanese civilization. What Huntington calls the "clash of civilizations" might be characterized by Wilkinson as a clash of cultural spheres within a single global civilization. Others point to the Crusading movement as
6765-515: The European colonization of the Americas and Australia. The term "primitive," though once used in anthropology , has now been largely condemned by anthropologists because of its derogatory connotations and because it implies that the cultures it refers to are relics of a past time that do not change or progress. Because of this, societies regarding themselves as "civilized" have sometimes sought to dominate and assimilate "uncivilized" cultures into
6888-423: The French civilisé ('civilized'), from Latin : civilis ('civil'), related to civis ('citizen') and civitas ('city'). The fundamental treatise is Norbert Elias 's The Civilizing Process (1939), which traces social mores from medieval courtly society to the early modern period . In The Philosophy of Civilization (1923), Albert Schweitzer outlines two opinions: one purely material and
7011-497: The German word Kultur , "culture", for what many call a "civilization". Spengler believed a civilization's coherence is based on a single primary cultural symbol. Cultures experience cycles of birth, life, decline, and death, often supplanted by a potent new culture, formed around a compelling new cultural symbol. Spengler states civilization is the beginning of the decline of a culture as "the most external and artificial states of which
7134-699: The Greek geographer Strabo , the Cynic philosopher Onesicritus of Astypalaea , who accompanied Alexander the Great 's conquests in India , reported that Patalene (the delta of the Indus River ) was "a delta" ( Koinē Greek : καλεῖ δὲ τὴν νῆσον δέλτα , romanized: kalei de tēn nēson délta , lit. 'he calls the island a delta'). The Roman author Arrian 's Indica states that "the delta of
7257-668: The Mississippi Delta, in order to eliminate land loss and mitigate coastal erosion, artificial diversions, reconnecting river to the deltaic wetland , have been constructed. Essentially, these diversions are expected to generate mouth bars at downstream end. Therefore, the restoration plans and studies by many scientists and engineers aim ultimately to promote mouth bar deposition by strategically selecting diversion sites and diversion geometries, and consequently stabilizing jet, enhancing bottom friction and sediment trapping efficiencies. This example shows how extremely essential
7380-501: The Mississippi. For example, a mountain river depositing sediment into a freshwater lake would form this kind of delta. It is commonly a result of homopycnal flow. Such deltas are characterized by a tripartite structure of topset, foreset, and bottomset beds. River water entering the lake rapidly deposits its coarser sediments on the submerged face of the delta, forming steeping dipping foreset beds. The finer sediments are deposited on
7503-472: The ability to pile up and accumulate due to the sediment traveling into a steep subduction trench rather than a shallow continental shelf . There are many other lesser factors that could explain why the majority of river deltas form along passive margins rather than active margins. Along active margins, orogenic sequences cause tectonic activity to form over-steepened slopes, brecciated rocks, and volcanic activity resulting in delta formation to exist closer to
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#17327733285297626-534: The active pursuit of progress characteristic of the Age of Enlightenment . In the late 1700s and early 1800s, during the French Revolution , "civilization" was used in the singular , never in the plural, and meant the progress of humanity as a whole. This is still the case in French. The use of "civilizations" as a countable noun was in occasional use in the 19th century, but has become much more common in
7749-458: The amount of energy a civilization is able to harness. The scale is only hypothetical, but it puts energy consumption in a cosmic perspective. The Kardashev scale makes provisions for civilizations far more technologically advanced than any currently known to exist. The current scientific consensus is that human beings are the only animal species with the cognitive ability to create civilizations that has emerged on Earth. A recent thought experiment,
7872-444: The bar, increased water and sediment discharges around the bar cause widening and creation of a classic triangular river mouth bar in plan view. Sediment erosion and deposition dynamics in estuarine region, consequently the formation and growth of mouth bars, are affected by several natural and artificial factors. Human activities, such as reservoir construction, large-scale reclamation and embankment construction completely disturb
7995-438: The basin water, the delta is characterized by homopycnal flow , in which the river water rapidly mixes with basin water and abruptly dumps most of its sediment load. Where the river water has a higher density than basin water, typically from a heavy load of sediment, the delta is characterized by hyperpycnal flow in which the river water hugs the basin bottom as a density current that deposits its sediments as turbidites . When
8118-1248: The basins feeding deltas have reduced river sediment delivery to many deltas in recent decades. This change means that there is less sediment available to maintain delta landforms, and compensate for erosion and sea level rise , causing some deltas to start losing land. Declines in river sediment delivery are projected to continue in the coming decades. The extensive anthropogenic activities in deltas also interfere with geomorphological and ecological delta processes. People living on deltas often construct flood defences which prevent sedimentation from floods on deltas, and therefore means that sediment deposition can not compensate for subsidence and erosion . In addition to interference with delta aggradation , pumping of groundwater , oil , and gas , and constructing infrastructure all accelerate subsidence , increasing relative sea level rise. Anthropogenic activities can also destabilise river channels through sand mining , and cause saltwater intrusion . There are small-scale efforts to correct these issues, improve delta environments and increase environmental sustainability through sedimentation enhancing strategies . While nearly all deltas have been impacted to some degree by humans,
8241-422: The bird's-foot of the Mississippi or Ural river deltas), pushing its mouth into the standing water. As the deltaic lobe advances, the gradient of the river channel becomes lower because the river channel is longer but has the same change in elevation (see slope ). As the gradient of the river channel decreases, the amount of shear stress on the bed decreases, which results in the deposition of sediment within
8364-415: The boundary between an upland stream and an estuary, in the region known as the "subestuary". Drowned coastal river valleys that were inundated by rising sea levels during the late Pleistocene and subsequent Holocene tend to have dendritic estuaries with many feeder tributaries. Each tributary mimics this salinity gradient from its brackish junction with the mainstem estuary up to the fresh stream feeding
8487-449: The channel and a rise in the channel bed relative to the floodplain . This destabilizes the river channel. If the river breaches its natural levees (such as during a flood), it spills out into a new course with a shorter route to the ocean, thereby obtaining a steeper, more stable gradient. Typically, when the river switches channels in this manner, some of its flow remains in the abandoned channel. Repeated channel-switching events build up
8610-607: The channel flow due to initial mouth bar formation forms new distributary channels and they extend as the mouth bar migrates. Lateral and upstream growth of mouth bar reduces the flow velocity and sediment flux, i.e., flow capacity to carry sediments, through that channel resulting in filling and abandonment of the terminal distributary channel. The active channel, where the flow is diverted into, bifurcates again, following formation of another mouth bar, and creates another unit of channels. Moreover, river mouth bars are important hydrocarbon reservoirs , and have been widely interpreted in
8733-532: The collapse of civilization. Some focus on historical examples, and others on general theory. According to political scientist Samuel P. Huntington , the 21st century will be characterized by a clash of civilizations , which he believes will replace the conflicts between nation-states and ideologies that were prominent in the 19th and 20th centuries. However, this viewpoint been strongly challenged by others such as Edward Said , Muhammed Asadi and Amartya Sen . Ronald Inglehart and Pippa Norris have argued that
8856-532: The conquest state". Traders and bureaucrats relied on writing to keep accurate records. Like money, the writing was necessitated by the size of the population of a city and the complexity of its commerce among people who are not all personally acquainted with each other. However, writing is not always necessary for civilization, as shown by the Inca civilization of the Andes, which did not use writing at all but except for
8979-429: The delta. Mississippi delta is composed of widely separated buoyancy-dominated mouth bar types in the south ( Southwest Pass and South Pass). Powerful and persistent wave energy and corresponding processes such as wave reworking, refraction of outflow, mixing due to wave breaking , longshore and cross-shore dispersion of sediment generate regular, commonly sand-filled, crescentic bars located at short distances from
9102-597: The destruction of cultural assets is also part of psychological warfare. The target of the attack is often the opponent's cultural identity, which is why symbolic cultural assets become a main target. It is also intended to destroy the particularly sensitive cultural memory (museums, archives, monuments, etc.), the grown cultural diversity, and the economic basis (such as tourism) of a state, region or community. Many historians have focused on these broad cultural spheres and have treated civilizations as discrete units. Early twentieth-century philosopher Oswald Spengler , uses
9225-478: The development of distinct mouth bar morphologies. River discharge , tides and waves can also simultaneously affect the outflow dynamics depending on buoyancy, which play an important role on the evolution of mouth bars. When a river-dominated delta is considered, formation and evolution of terminal distributary channels of the delta, which are the most active parts of the distributive channel network, are closely related to mouth bar formation. Bifurcation of
9348-634: The development of state structures, in which power was further monopolized by an elite ruling class who practiced human sacrifice. Towards the end of the Neolithic period, various elitist Chalcolithic civilizations began to rise in various "cradles" from around 3600 BCE beginning with Mesopotamia , expanding into large-scale kingdoms and empires in the course of the Bronze Age ( Akkadian Empire , Indus Valley Civilization , Old Kingdom of Egypt , Neo-Sumerian Empire , Middle Assyrian Empire , Babylonian Empire , Hittite Empire , and to some degree
9471-746: The displacement of Indigenous Australians by observing that the land appeared uncultivated and wild, which to them reflected that the inhabitants were not civilized enough to "improve" it. The behaviors and modes of subsistence that characterize civilization have been spread by colonization , invasion , religious conversion , the extension of bureaucratic control and trade , and by the introduction of new technologies to cultures that did not previously have them. Though aspects of culture associated with civilization can be freely adopted through contact between cultures, since early modern times Eurocentric ideals of "civilization" have been widely imposed upon cultures through coercion and dominance. These ideals complemented
9594-409: The early Iron Age , contemporary civilizations developed money as a medium of exchange for increasingly complex transactions. In a village, the potter makes a pot for the brewer and the brewer compensates the potter by giving him a certain amount of beer. In a city, the potter may need a new roof, the roofer may need new shoes, the cobbler may need new horseshoes, the blacksmith may need a new coat and
9717-616: The economy due to their well-sorted sand and gravel . Sand and gravel are often quarried from these old deltas and used in concrete for highways , buildings, sidewalks, and landscaping. More than 1 billion tons of sand and gravel are produced in the United States alone. Not all sand and gravel quarries are former deltas, but for ones that are, much of the sorting is already done by the power of water. Urban areas and human habitation tend to be located in lowlands near water access for transportation and sanitation . This makes deltas
9840-482: The energy of slaves to plant crops, clothe emperors, and build cities" and considers slavery to be a common feature of pre-modern civilizations. All civilizations have depended on agriculture for subsistence, with the possible exception of some early civilizations in Peru which may have depended upon maritime resources. The traditional "surplus model" postulates that cereal farming results in accumulated storage and
9963-438: The failure of a "creative minority", through moral or religious decline, to meet some important challenge, rather than mere economic or environmental causes. Samuel P. Huntington defines civilization as "the highest cultural grouping of people and the broadest level of cultural identity people have short of that which distinguishes humans from other species". Another group of theorists, making use of systems theory , looks at
10086-485: The first step in globalization. The more conventional viewpoint is that networks of societies have expanded and shrunk since ancient times , and that the current globalized economy and culture is a product of recent European colonialism . The notion of human history as a succession of "civilizations" is an entirely modern one. In the European Age of Discovery , emerging Modernity was put into stark contrast with
10209-412: The flow enters the standing water, it is no longer confined to its channel and expands in width. This flow expansion results in a decrease in the flow velocity , which diminishes the ability of the flow to transport sediment . As a result, sediment drops out of the flow and is deposited as alluvium , which builds up to form the river delta. Over time, this single channel builds a deltaic lobe (such as
10332-485: The food surplus through decreasing rural population growth in favour of urban growth. Suitability of highly productive roots and tubers was in fact a curse of plenty, which prevented the emergence of states and impeded economic development. A surplus of food permits some people to do things besides producing food for a living: early civilizations included soldiers , artisans , priests and priestesses, and other people with specialized careers. A surplus of food results in
10455-409: The growing gulf between rich and poor. Cultural critic and author Derrick Jensen argues that modern civilization is directed towards the domination of the environment and humanity itself in an intrinsically harmful, unsustainable, and self-destructive fashion. Defending his definition both linguistically and historically, he defines civilization as "a culture... that both leads to and emerges from
10578-671: The growth of cities", with "cities" defined as "people living more or less permanently in one place in densities high enough to require the routine importation of food and other necessities of life". This need for civilizations to import ever more resources, he argues, stems from their over-exploitation and diminution of their own local resources. Therefore, civilizations inherently adopt imperialist and expansionist policies and, to maintain these, highly militarized, hierarchically structured, and coercion-based cultures and lifestyles. The Kardashev scale classifies civilizations based on their level of technological advancement, specifically measured by
10701-478: The head of tidal propagation. As a result, the tributaries are considered to be "subestuaries". The origin and evolution of a tidal freshwater delta involves processes that are typical of all deltas as well as processes that are unique to the tidal freshwater setting. The combination of processes that create a tidal freshwater delta result in a distinct morphology and unique environmental characteristics. Many tidal freshwater deltas that exist today are directly caused by
10824-686: The hydrodynamic balance of the system and permanently interfere with the morphology of mouth bars. Moreover, hydrodynamic factors such as water runoff , discharge fluctuations of the rivers, i.e., non-uniform flow conditions linked to the river hydrograph , sediment flux, sediment characteristics, river mouth geometry, vegetation, existence of tides and waves, play a vital role in sediment erosion and deposition dynamics at river mouths and activate serious geomorphologic controls on mouth bar development. Regarding sediment characteristics, mass and cohesiveness play important roles in river mouth bar evolution. Since coarser sediments are not well suspended by
10947-408: The jet, they are likely to deposit close to the river mouth and lead to mouth bar construction. On the other hand, since fine sediments are generally transported in a suspended form, they can be carried further and disperse widely, and most of the time, lead to levee construction. Moreover, sediment cohesion, and similarly vegetation , play a role in the morphology of river mouth deposits by enhancing
11070-403: The lake bottom beyond this steep slope as more gently dipping bottomset beds. Behind the delta front, braided channels deposit the gently dipping beds of the topset on the delta plain. While some authors describe both lacustrine and marine locations of Gilbert deltas, others note that their formation is more characteristic of the freshwater lakes, where it is easier for the river water to mix with
11193-592: The lakewater faster (as opposed to the case of a river falling into the sea or a salt lake, where less dense fresh water brought by the river stays on top longer). Gilbert himself first described this type of delta on Lake Bonneville in 1885. Elsewhere, similar structures occur, for example, at the mouths of several creeks that flow into Okanagan Lake in British Columbia and form prominent peninsulas at Naramata , Summerland , and Peachland . In wave-dominated deltas, wave-driven sediment transport controls
11316-581: The land of the Indians is made by the Indus river no less than is the case with that of Egypt". As a generic term for the landform at the mouth of the river, the word delta is first attested in the English-speaking world in the late 18th century, in the work of Edward Gibbon . River deltas form when a river carrying sediment reaches a body of water, such as a lake, ocean, or a reservoir . When
11439-408: The land. Because a percentage of people in civilizations do not grow their own food, they must trade their goods and services for food in a market system, or receive food through the levy of tribute , redistributive taxation , tariffs or tithes from the food producing segment of the population. Early human cultures functioned through a gift economy supplemented by limited barter systems. By
11562-543: The later 20th century, sometimes just meaning culture (itself in origin an uncountable noun, made countable in the context of ethnography ). Only in this generalized sense does it become possible to speak of a "medieval civilization", which in Elias's sense would have been an oxymoron. Using the terms "civilization" and "culture" as equivalents are controversial and generally rejected so that for example some types of culture are not normally described as civilizations. Already in
11685-533: The living standards of the populace. For example, although the Middle Ages is often portrayed as an era of decline from the Roman Empire, studies have shown that the average stature of males in the Middle Ages (c. 500 to 1500 CE) was greater than it was for males during the preceding Roman Empire and the succeeding Early Modern Period (c. 1500 to 1800 CE). Also, the Plains Indians of North America in
11808-426: The main control on deposition, which is a combination of river, wave , and tidal processes, depending on the strength of each. The other two factors that play a major role are landscape position and the grain size distribution of the source sediment entering the delta from the river. Fluvial-dominated deltas are found in areas of low tidal range and low wave energy. Where the river water is nearly equal in density to
11931-518: The many others identities that make up people and leads to a focus on differences. Cultural Historian Morris Berman argues in Dark Ages America: the End of Empire that in the corporate consumerist United States, the very factors that once propelled it to greatness―extreme individualism, territorial and economic expansion, and the pursuit of material wealth―have pushed the United States across
12054-580: The morphology of estuaries. Therefore, the understanding of mouth bar evolution is key for further and better quantification of the changes in river hydraulics and morphodynamics due to mouth bar existence. Mouth bars are categorized based on the primary forces dominating their formation: (1) outflow inertia, (2) turbulent bed friction, (3) effluent buoyancy , (4) wave-induced, and finally, (5) tidal forces. Processes linked to high outflow velocities at deep water outlet and dispersion of sediment due to turbulent jet produce narrow, elongated lunate bars with
12177-477: The mouth. The shape and location of the mouth bar also changes with normal or oblique wave incidence. The development of tidal-dominated river mouth bars highly depends on the bidirectional sediment transport by tidal currents causing significant upstream return of sediment into channel. Flood and ebb-dominated sediment transports generate a broad, discontinuous, radial mouth bar dominated by large tidal ridges separated by deep channels. River mouth bar evolution
12300-451: The mouths of the bifurcated channels and enhance basinward the delta growth. Mississippi Delta is composed of shallow-water friction-dominated types in the east (Northeast Pass). Dominance of buoyancy processes at the river mouth associated with strong outflow density stratification and fine-grained sediment load rather than bed load , produces laterally restricted, narrow radial bars with gently dipping slopes in shallow water areas of
12423-520: The onset of or changes in historical land use, especially deforestation , intensive agriculture , and urbanization . These ideas are well illustrated by the many tidal freshwater deltas prograding into Chesapeake Bay along the east coastline of the United States. Research has demonstrated that the accumulating sediments in this estuary derive from post-European settlement deforestation, agriculture, and urban development. Other rivers, particularly those on coasts with significant tidal range , do not form
12546-407: The other hand, depend on the relative strength of river inertia with respect to the tidal energy. When tidal energy is much higher than the fluvial one, hydrodynamics of the jet exiting the river mouth, dominating the sediment deposition, are highly affected. Continuously altered tidal wave velocity, width of spreading jet, water depth, and therefore, bottom friction throughout the tidal cycle, cause
12669-475: The other material and ethical . He said that the world crisis was from humanity losing the ethical idea of civilization, "the sum total of all progress made by man in every sphere of action and from every point of view in so far as the progress helps towards the spiritual perfecting of individuals as the progress of all progress". Related words like "civility" developed in the mid-16th century. The abstract noun "civilization", meaning "civilized condition", came in
12792-498: The rapid development of hierarchies , and the use of human sacrifice . The civilized urban revolution in turn was dependent upon the development of sedentism , the domestication of grains, plants and animals, the permanence of settlements and development of lifestyles that facilitated economies of scale and accumulation of surplus production by particular social sectors. The transition from complex cultures to civilizations , while still disputed, seems to be associated with
12915-451: The relative importance of the inertia of rapidly flowing water, the importance of turbulent bed friction beyond the river mouth, and buoyancy . Outflow dominated by inertia tends to form Gilbert-type deltas. Outflow dominated by turbulent friction is prone to channel bifurcation, while buoyancy-dominated outflow produces long distributaries with narrow subaqueous natural levees and few channel bifurcations. The modern Mississippi River delta
13038-487: The result of this process is the Wax Lake Delta . In both of these cases, depositional processes force redistribution of deposition from areas of high deposition to areas of low deposition. This results in the smoothing of the planform (or map-view) shape of the delta as the channels move across its surface and deposit sediment. Because the sediment is laid down in this fashion, the shape of these deltas approximates
13161-575: The river delta, causing the delta to retreat. For deltas that form further upriver in an estuary, there are complex yet quantifiable linkages between winds, tides, river discharge, and delta water levels. Erosion is also an important control in tide-dominated deltas, such as the Ganges Delta , which may be mainly submarine, with prominent sandbars and ridges. This tends to produce a "dendritic" structure. Tidal deltas behave differently from river-dominated and wave-dominated deltas, which tend to have
13284-435: The river mouth bar. In addition to the controls related to fluvial processes , the effects of marine controls, such as wave activity and tides, on river mouths are significant on the mouth bar evolution. Waves have a double effect on mouth bar growth; while small and locally generated waves favor the bar formation by increasing the jet spreading, large, swell waves suppress bar development. The complex effects of tides, on
13407-482: The river water is less dense than the basin water, as is typical of river deltas on an ocean coastline, the delta is characterized by hypopycnal flow in which the river water is slow to mix with the denser basin water and spreads out as a surface fan. This allows fine sediments to be carried a considerable distance before settling out of suspension. Beds in a hypocynal delta dip at a very shallow angle, around 1 degree. Fluvial-dominated deltas are further distinguished by
13530-478: The sediment is never piled up in thick sequences due to the sediment traveling and depositing in deep subduction trenches. At the mouth of a river, the change in flow conditions can cause the river to drop any sediment it is carrying. This sediment deposition can generate a variety of landforms, such as deltas, sand bars, spits, and tie channels. Landforms at the river mouth drastically alter the geomorphology and ecosystem. Deltas are typically classified according to
13653-510: The sediment source. When sediment does not travel far from the source, sediments that build up are coarser grained and more loosely consolidated, therefore making delta formation more difficult. Tectonic activity on active margins causes the formation of river deltas to form closer to the sediment source which may affect channel avulsion , delta lobe switching, and auto cyclicity. Active margin river deltas tend to be much smaller and less abundant but may transport similar amounts of sediment. However,
13776-423: The shape of the delta, and much of the sediment emanating from the river mouth is deflected along the coastline. The relationship between waves and river deltas is quite variable and largely influenced by the deepwater wave regimes of the receiving basin. With a high wave energy near shore and a steeper slope offshore, waves will make river deltas smoother. Waves can also be responsible for carrying sediments away from
13899-440: The stabilization, consequently changing the hydraulic geometry of the mouth and altering the hydrodynamics of the jet. Grain size , which controls the settling velocity of the particles, also influences the location of the river mouth bar basinward of the outlet. In addition, model results recently suggest that river channel width, depth, outflow velocity, and basin slope are the most important variables influencing distance to
14022-594: The surplus and exercises its will through the actions of a government or bureaucracy . Morton Fried , a conflict theorist and Elman Service , an integration theorist, have classified human cultures based on political systems and social inequality . This system of classification contains four categories. Economically, civilizations display more complex patterns of ownership and exchange than less organized societies. Living in one place allows people to accumulate more personal possessions than nomadic people. Some people also acquire landed property , or private ownership of
14145-486: The tanner may need a new pot. These people may not be personally acquainted with one another and their needs may not occur all at the same time. A monetary system is a way of organizing these obligations to ensure that they are fulfilled. From the days of the earliest monetarized civilizations, monopolistic controls of monetary systems have benefited the social and political elites. The transition from simpler to more complex economies does not necessarily mean an improvement in
14268-839: The territorial expansions of the Elamites , Hurrians , Amorites and Ebla ). Outside the Old World, development took place independently in the Pre-Columbian Americas . Urbanization in the Caral-Supe civilization in coastal Peru began about 3500 BCE. In North America, the Olmec civilization emerged about 1200 BCE; the oldest known Mayan city, located in Guatemala, dates to about 750 BCE. and Teotihuacan in Mexico
14391-654: The trailing edges of passive margins due to the majority of large rivers such as the Mississippi , Nile , Amazon , Ganges , Indus , Yangtze , and Yellow River discharging along passive continental margins. This phenomenon is due mainly to three factors: topography , basin area, and basin elevation. Topography along passive margins tend to be more gradual and widespread over a greater area enabling sediment to pile up and accumulate over time to form large river deltas. Topography along active margins tends to be steeper and less widespread, which results in sediments not having
14514-410: The upstream bar face and deposition in the downstream bar wake ; (3) River mouth bar progradation stops and it stagnates when depth over the bar is shallow enough to create a fluid pressure on the upstream side of the bar forcing flow around the bar, and consequently decreasing velocity and shear stress over the bar top; (4) Finally, as the levees continue to grow and spread due to the presence of
14637-518: The wheel, the building of the earliest cities and the development of written cursive script". Similar pre-civilized "neolithic revolutions" also began independently from 7,000 BCE in northwestern South America (the Caral-Supe civilization ) and in Mesoamerica . The Black Sea area served as a cradle of European civilization. The site of Solnitsata – a prehistoric fortified ( walled ) stone settlement (prehistoric proto-city ) (5500–4200 BCE) –
14760-498: The world, incorporating earlier cultures into the technological and industrial society of the present. Civilizations are traditionally understood as ending in one of two ways; either through incorporation into another expanding civilization (e.g. as Ancient Egypt was incorporated into Hellenistic Greek, and subsequently Roman civilizations), or by collapsing and reverting to a simpler form of living, as happens in so-called Dark Ages. There have been many explanations put forward for
14883-506: Was behind Nazism and German militarism and nihilism . Social scientists such as V. Gordon Childe have named a number of traits that distinguish a civilization from other kinds of society. Civilizations have been distinguished by their means of subsistence, types of livelihood , settlement patterns, forms of government , social stratification , economic systems, literacy and other cultural traits. Andrew Nikiforuk argues that "civilizations relied on shackled human muscle. It took
15006-726: Was first coined by Alexander von Humboldt for the middle reaches of the Orinoco River , which he visited in 1800. Other prominent examples include the Inner Niger Delta , Peace–Athabasca Delta , the Sacramento–San Joaquin River Delta , and the Sistan delta of Iran. The Danube has one in the valley on the Slovak–Hungarian border between Bratislava and Iža . In some cases, a river flowing into
15129-771: Was one of the largest cities in the world in 350 CE, with a population of about 125,000. The Bronze Age collapse was followed by the Iron Age around 1200 BCE, during which a number of new civilizations emerged, culminating in a period from the 8th to the 3rd century BCE which Karl Jaspers termed the Axial Age , presented as a critical transitional phase leading to classical civilization . A major technological and cultural transition to modernity began approximately 1500 CE in Western Europe , and from this beginning new approaches to science and law spread rapidly around
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