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81-456: The site of Spina was lost until modern times, when drainage schemes in the delta of the Po River in 1922 first officially revealed a necropolis of Etruscan Spina about four miles west of the commune of Comacchio . The fishermen of Comacchio, it soon turned out, had been the source of "Etruscan" vases (actually ancient imports from Greece) and other artifacts that had appeared for years on

162-432: A density current that deposits its sediments as turbidites . When 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

243-569: A festival called the Dionysia , which honoured the god Dionysus . Tragedy (late 500 BC), comedy (490 BC), and the satyr play were the three dramatic genres emerged there. Athens exported the festival to its numerous colonies. Modern Western theatre comes, in large measure, from the theatre of ancient Greece , from which it borrows technical terminology, classification into genres, and many of its themes , stock characters , and plot elements. The word τραγῳδία , tragodia , from which

324-484: A comedy. Aristotle claimed that Aeschylus added the second actor ( deuteragonist ), and that Sophocles introduced the third ( tritagonist ). Apparently, the Greek playwrights never used more than three actors based on what is known about Greek theatre. Tragedy and comedy were viewed as completely separate genres, and no plays ever merged aspects of the two. Satyr plays dealt with the mythological subject matter of

405-493: 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

486-545: 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

567-533: 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

648-399: 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

729-545: 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

810-580: A hill, producing a natural viewing area known as the theatron (literally "seeing place"). In cities without suitable hills, banks of earth were piled up. At the foot of the hill was a flattened, generally circular performance space with an average diameter of 78 feet (24 m), known as the orchestra (literally "dancing place"), where a chorus of typically 12 to 15 people performed plays in verse accompanied by music. There were often tall, arched entrances called parodoi or eisodoi , through which actors and chorus members entered and exited

891-573: A hypocynal delta dip at a very shallow angle, around 1 degree. Fluvial-dominated deltas are further distinguished by 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

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972-439: 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

1053-524: A play entitled The Fall of Miletus and produced it, the whole theatre fell to weeping; they fined Phrynichus a thousand drachmas for bringing to mind a calamity that affected them so personally and forbade the performance of that play forever." He is also thought to be the first to use female characters (though not female performers). Until the Hellenistic period , all tragedies were unique pieces written in honour of Dionysus and played only once; what

1134-563: A play, such as the Furies in Aeschylus ' Eumenides and Pentheus and Cadmus in Euripides ' The Bacchae . Worn by the chorus, the masks created a sense of unity and uniformity, while representing a multi-voiced persona or single organism and simultaneously encouraged interdependency and a heightened sensitivity between each individual of the group. Only 2 to 3 actors were allowed on

1215-419: A result the disastrous spring floods were mitigated. Much other evidence of Etruscan hydraulic engineering works remains in the area. They have drained the marshes and provided irrigation for dry lands. 44°41′35″N 12°06′04″E  /  44.6930555556°N 12.1011111111°E  / 44.6930555556; 12.1011111111 River delta A river delta is a triangular landform created by

1296-423: A sedimentary deposit formed at 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

1377-447: 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

1458-551: 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

1539-439: 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. Ancient Greek drama A theatrical culture flourished in ancient Greece from 700 BC. At its centre was the city-state of Athens , which became a significant cultural, political, and religious place during this period, and the theatre was institutionalised there as part of

1620-591: 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

1701-522: Is normally regarded as the Golden Age of Greek drama. The center-piece of the annual Dionysia , which took place once in winter and once in spring, was a competition between three tragic playwrights at the Theatre of Dionysus . Each submitted three tragedies, plus a satyr play (a comic, burlesque version of a mythological subject). Beginning in a first competition in 486 BC each playwright submitted

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1782-542: Is presently known, was created in Athens around 532 BC, when Thespis was the earliest recorded actor. Being a winner of the first theatrical contest held in Athens, he was the exarchon , or leader, of the dithyrambs performed in and around Attica, especially at the Rural Dionysia . By Thespis' time, the dithyramb had evolved far away from its cult roots. Under the influence of heroic epic, Doric choral lyric and

1863-645: Is primarily extant today are the pieces that were still remembered well enough to have been repeated when the repetition of old tragedies became fashionable (the accidents of survival, as well as the subjective tastes of the Hellenistic librarians later in Greek history, also played a role in what survived from this period). After the Achaemenid destruction of Athens in 480 BC, the town and acropolis were rebuilt, and theatre became formalized and an even greater part of Athenian culture and civic pride. This century

1944-548: 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

2025-538: Is the Pronomos Vase where actors are painted at a show's after party. Costuming would give off a sense of character, as in gender, age, social status, and class. For example, characters of higher class would be dressed in nicer clothing, although everyone was dressed fairly nicely. Contrary to popular belief, they did not dress in only rags and sandals, as they wanted to impress. Some examples of Greek theatre costuming include long robes called chiton that reached

2106-599: Is unclear at best, but his name has been given a longer life in English as a common term for performer—i.e., a "thespian." The dramatic performances were important to the Athenians – this is made clear by the creation of a tragedy competition and festival in the City Dionysia (or Great Dionysia). This was organized possibly to foster loyalty among the tribes of Attica (recently created by Cleisthenes ). The festival

2187-582: The Golden Age such as the Danaids , Phoenician Women and Alcestis . He was the first poet we know of to use a historical subject – his Fall of Miletus , produced in 493–2, chronicled the fate of the town of Miletus after it was conquered by the Persians. Herodotus reports that "the Athenians made clear their deep grief for the taking of Miletus in many ways, but especially in this: when Phrynichus wrote

2268-662: 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

2349-532: 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

2430-411: 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

2511-470: The 1960s. Greek mask-maker Thanos Vovolis suggests that the mask serves as a resonator for the head, thus enhancing vocal acoustics and altering its quality. This leads to increased energy and presence, allowing for the more complete metamorphosis of the actor into his character. In a large open-air theatre, like the Theatre of Dionysus in Athens , the classical masks were able to create a sense of dread in

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2592-648: 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

2673-503: 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

2754-472: 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

2835-474: The actors' voices could be heard throughout the theatre, including the very top row of seats. The Greek's understanding of acoustics compares very favorably with the current state of the art . There were several scenic elements commonly used in Greek theatre: The Ancient Greek term for a mask is prosopon (lit., "face"), and was a significant element in the worship of Dionysus at Athens likely used in ceremonial rites and celebrations. Many masks worshipped

2916-400: The altar of Dionysus after performances. Nevertheless, the mask is known to have been used since the time of Aeschylus and considered to be one of the iconic conventions of classical Greek theatre. Masks were also made for members of the chorus, who play some part in the action and provide a commentary on the events in which they are caught up. Although there are twelve or fifteen members of

2997-420: The archeological black market . The archaeological finds from the burials of Spina were discovered with the help of aerial photography . Aside from the white reflective surfaces of the modern drainage channels there appeared in the photographs a ghostly network of dark lines and light rectangles, the former indicating richer vegetation on the sites of ancient canals . Thus the layout of the ancient trading port

3078-542: The audience creating large scale panic, especially since they had intensely exaggerated facial features and expressions. They enabled an actor to appear and reappear in several different roles, thus preventing the audience from identifying the actor to one specific character. Their variations help the audience to distinguish sex, age, and social status, in addition to revealing a change in a particular character's appearance, e.g., Oedipus , after blinding himself. Unique masks were also created for specific characters and events in

3159-1256: 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,

3240-601: The bigger Etruscan city of Felsina (ancient name of Bologna ). The city was at the southern end of the ancient Amber Road from the Baltic Sea. This trade was done through the Veneti , whose cities were to the north. They also traded in horses, for which the Veneti were famous. Etruscan hydraulic engineers managed to confine the wide Po river at Spina to its bed, by the means of constructing many canals to direct its flow. As

3321-422: 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

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3402-433: The bottom of the theatron where the chorus and actors performed; the word means "dancing space", as the chorus also danced in early periods. Originally unraised, Greek theatre would later incorporate a raised stage for easier viewing. This practice would become common after the advent of "New Comedy," which incorporated dramatic portrayal of individual characters. The coryphaeus was the head chorus member, who could enter

3483-450: 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

3564-619: 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

3645-789: 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. 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

3726-454: The floor for actors playing gods, heroes, and old men. Actors playing goddesses and women characters that held a lot of power wore purple and gold. Actors playing queens and princesses wore long cloaks that dragged on the ground and were decorated with gold stars and other jewels, and warriors were dressed in a variety of armor and wore helmets adorned with plumes. Costumes were supposed to be colourful and obvious to be easily seen by every seat in

3807-414: 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

3888-506: The fresh stream feeding 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

3969-466: The geomorphology and ecosystem. Deltas are typically classified according to 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

4050-555: The higher power, the gods, making masks also very important for religion. Most of the evidence comes from only a few vase paintings of the 5th century BC, such as one showing a mask of the god suspended from a tree with decorated robe hanging below it and dancing and the Pronomos vase, which depicts actors preparing for a satyr play . No physical evidence remains available to us, as the masks were made of organic materials and not considered permanent objects, ultimately being dedicated at

4131-545: The innovations of the poet Arion , it had become a narrative, ballad-like genre. Because of these, Thespis is often called the "Inventor of Tragedy"; however, his importance is disputed, and Thespis is sometimes listed as late as 16th in the chronological order of Greek tragedians; the statesman Solon , for example, is credited with creating poems in which characters speak with their own voice, and spoken performances of Homer 's epics by rhapsodes were popular in festivals prior to 534 BC. Thus, Thespis's true contribution to drama

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4212-406: 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

4293-594: 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

4374-583: 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

4455-411: The masked actor from the theatrical character. The mask-makers were called skeuopoios or "maker of the props", thus suggesting that their role encompassed multiple duties and tasks. The masks were most likely made out of light weight, organic materials like stiffened linen, leather, wood, or cork, with the wig consisting of human or animal hair. Due to the visual restrictions imposed by these masks, it

4536-447: The mouth and an integrated wig. These paintings never show actual masks on the actors in performance. They are most often shown being handled by the actors before or after a performance. This demonstrates the way in which the mask was to 'melt' into the face and allow the actor to vanish into the role. Effectively, the mask transformed the actor as much as memorization of the text. Therefore, performance in ancient Greece did not distinguish

4617-524: 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

4698-443: The orchestra and also served as an area where actors could change their costumes. After 425 BC a stone scene wall, called a paraskenia , became a common supplement to skené . The paraskenia was a long wall with projecting sides, which may have had doorways for entrances and exits. Just behind the paraskenia was the proskenion ("in front of the scene"), which is similar to the modern day proscenium . The upper story

4779-423: The orchestra. In some theatres, behind the orchestra, was a backdrop or scenic wall known as the skené . The term theatre eventually came to mean the whole area of theatron , orchestra , and skené . The theatron was the seating area, built into a hill to create a natural viewing space. The first seats in Greek theatres (other than just sitting on the ground) were wooden, but around 499 BC,

4860-735: The other actors. The actors with comedic roles only wore a thin-soled shoe called a soccus or sock. For this reason, dramatic art is sometimes called " sock and buskin ." Male actors playing female roles would wear a wooden structure on their chests ( posterneda ) to imitate the look of breasts and another structure on their stomachs ( progastreda ) to make them appear softer and more lady like. They would also wear white body stockings under their costumes to make their skin appear fairer. Most costuming detail comes from pottery paintings from that time as costumes and masks were fabricated out of disposable material, so there are little to no remains of any costume from that time. The biggest source of information

4941-502: The power of the spoken word, and it was their main method of communication and storytelling. Bahn and Bahn write, "To Greeks, the spoken word was a living thing and infinitely preferable to the dead symbols of a written language." Socrates himself believed that once something has been written down, it lost its ability for change and growth. For these reasons, among many others, oral storytelling flourished in Greece. Greek tragedy , as it

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5022-442: The practice of inlaying stone blocks into the side of the hill to create permanent, stable seating became more common. They were called the prohedria and reserved for priests and a few of the most respected citizens. The diazoma separated the upper and lower seating areas. After 465 BC, playwrights began using a backdrop or scenic wall, called the skené (from which the word scene derives), that hung or stood behind

5103-487: 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

5184-579: 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

5265-414: The river water is nearly equal in density to 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

5346-399: 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

5427-514: 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,

5508-424: 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

5589-435: The stage at one time, and masks permitted quick transitions from one character to another. There were only male actors, but masks allowed them to play female characters. The modern method to interpret a role by switching between a few simple characters goes back to changing masks in the theatre of ancient Greece. The actors in these plays that had tragic roles wore boots called cothurnus ( buskin ), that elevated them above

5670-439: The story as a character able to interact with the characters of a play. Plays often began in the morning and lasted into the evening. The theatres were built on a large scale to accommodate a large number of performers on stage and in the audience—up to fourteen thousand . Physics and mathematics played a significant role in the construction of these theatres, as their designers had to be able to create acoustics in them such that

5751-529: The tragedies, but in a purely comedic manner. The power of Athens declined following its defeat in the Peloponnesian War against Sparta . From that time on, the theatre started performing old tragedies again. Although its theatrical traditions seem to have lost their vitality, Greek theatre continued into the Hellenistic period (the period following Alexander the Great 's conquests in the fourth century BC). The primary Hellenistic theatrical form

5832-415: The tragic chorus, they all wear the same mask because they are considered to be representing one character. Stylized comedy and tragedy masks said to originate in ancient Greek theatre have come to widely symbolize the performing arts generally. Illustrations of theatrical masks from 5th century display helmet-like masks, covering the entire face and head, with holes for the eyes and a small aperture for

5913-656: 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

5994-432: The word " tragedy " is derived, is a compound of two Greek words: τράγος , tragos or "goat" and ᾠδή , ode meaning "song", from ἀείδειν , aeidein , 'to sing'. This etymology indicates a link with the practices of the ancient Dionysian cults . It is impossible, however, to know with certainty how these fertility rituals became the basis for tragedy and comedy . The Ancient Greeks valued

6075-518: Was called the episkenion . Some theatres also had a raised speaking place on the orchestra called the logeion . By the end of the 5th century BC, around the time of the Peloponnesian War, the skené was two stories high. The death of a character was always heard behind the skené , for it was considered inappropriate to show a killing in view of the audience. Conversely, there are scholarly arguments that death in Greek tragedy

6156-409: Was created roughly around 508 BC. While no drama texts exist from the sixth century BC, the names of three competitors besides Thespis are known: Choerilus, Pratinas, and Phrynichus . Each is credited with different innovations in the field. Some information is known about Phrynichus. He won his first competition between 511 BC and 508 BC. He produced tragedies on themes and subjects later exploited in

6237-732: 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

6318-416: Was imperative that the actors hear in order to orient and balance themselves. Thus, it is believed that the ears were covered by substantial amounts of hair and not the helmet-mask itself. The mouth opening was relatively small, preventing the mouth being seen during performances. Vervain and Wiles posit that this small size discourages the idea that the mask functioned as a megaphone, as originally presented in

6399-408: Was not tragedy but New Comedy , comic episodes about the lives of ordinary citizens. The only extant playwright from the period is Menander . One of New Comedy's most important contributions was its influence on Roman comedy, an influence that can be seen in the surviving works of Plautus and Terence . Most ancient Greek cities lay on or near hills, so seating was generally built into the slope of

6480-399: Was portrayed off stage primarily because of dramatic considerations, and not prudishness or sensitivity of the audience. A temple nearby, especially on the right side of the scene, is almost always part of the Greek theatre complex. This could justify, as a transposition, the recurrence of the pediment with the later solidified stone scene. The orchestra was a circular piece of ground at

6561-600: Was revealed, now miles from the sea, due to the sedimentation of the Po delta. Spina was founded around 525 BC, soon after Adria . Despite the Greek foundation story mentioned by Pliny the Elder , it had a predominantly Etruscan population, but also a significant Greek presence. The population of Spina became significantly Hellenised . The city built a treasury in Delphi . Many of the goods imported through Spina were destined for

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