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126-483: The dunes of Lençóis are an important area of environmental preservation. Also of interest is the state capital of São Luís , which is a UNESCO World Heritage Site. Another important conservation area is the Parnaíba River delta, between the states of Maranhão and Piauí, with its lagoons , desert dunes and deserted beaches or islands, such as Caju island, which shelters rare birds. The northern portion of

252-423: A Portuguese hereditary captaincy . The first European settlement, however, was made by a French trading expedition under Jacques Riffault , of Dieppe , in 1594, who lost two of his three vessels in the vicinity of São Luís Island , and left a part of his men on that island when he returned home. Subsequently, Daniel de La Touche, Seigneur de La Rividière was sent to report on the place, and was then commissioned by

378-487: A DNA study from 2005, the average ancestral composition of São Luís , the biggest city in Maranhão, is 42% European, 39% native American and 19% African. Religion in Maranhão (2010) According to the 2010 Brazilian Census, most of the population (74.5%) is Roman Catholic , other religious groups include Protestants or evangelicals (17.2%), Spiritists (0.2%), Nones 6.3%, and people with other religions (1.8). Portuguese

504-562: A dune forms, plant succession occurs. The conditions on an embryo dune are harsh, with salt spray from the sea carried on strong winds. The dune is well drained and often dry, and composed of calcium carbonate from seashells. Rotting seaweed , brought in by storm waves adds nutrients to allow pioneer species to colonize the dune. For example, in the United Kingdom these pioneer species are often marram grass , sea wort grass and other sea grasses. These plants are well adapted to

630-537: A few days downriver by ascending another river to the north. De Orellana took about 57 men, the boat, and some canoes and left Pizarro's troops on 26 December 1541. However, De Orellana missed the confluence (probably with the Aguarico ) where he was searching supplies for his men. By the time he and his men reached another village, many of them were sick from hunger and eating "noxious plants", and near death. Seven men died in that village. His men threatened to mutiny if

756-708: A few hills, and the river enters the enormous Amazon rainforest . Although the Ucayali–Marañón confluence is the point at which most geographers place the beginning of the Amazon River proper, in Brazil the river is known at this point as the Solimões das Águas . The river systems and flood plains in Brazil, Peru, Ecuador, Colombia, and Venezuela, whose waters drain into the Solimões and its tributaries, are called

882-590: A few tens of metres except at their nose, where vegetation stops or slows the advance of accumulating sand. Simple parabolic dunes have only one set of arms that trail upwind, behind the leading nose. Compound parabolic dunes are coalesced features with several sets of trailing arms. Complex parabolic dunes include subsidiary superposed or coalesced forms, usually of barchanoid or linear shapes. Parabolic dunes, like crescent dunes, occur in areas where very strong winds are mostly unidirectional. Although these dunes are found in areas now characterized by variable wind speeds,

1008-469: A fourth found it profitable to navigate some of the smaller streams. In that same period, the Amazonas Company was increasing its fleet. Meanwhile, private individuals were building and running small steam craft of their own on the main river as well as on many of its tributaries. On 31 July 1867, the government of Brazil, constantly pressed by the maritime powers and by the countries encircling

1134-407: A low-lying pan within the basin where the water evaporates, depositing the gypsum and forming crystals known as selenite . The crystals left behind by this process are eroded by the wind and deposited as vast white dune fields that resemble snow-covered landscapes. These types of dune are rare, and only form in closed arid basins that retain the highly soluble gypsum that would otherwise be washed into

1260-491: A population of 1.9 million people in 2014, Manaus is the largest city on the Amazon. Manaus alone makes up approximately 50% of the population of the largest Brazilian state of Amazonas . The racial makeup of the city is 64% pardo (mulatto and mestizo) and 32% white . Although the Amazon river remains undammed, around 412 dams are in operation on the Amazon's tributary rivers. Of these 412 dams, 151 are constructed over six of

1386-519: A result of a civil war in 1684 for their opposition to the enslavement of the Indians. Ceará was subsequently detached, but the State of Maranhão remained separate until 1774, when it again became subject to the colonial administration of Brazil. In the late 18th century, there was a great influx of enslaved peoples into the region, which corresponded to the increased cultivation of cotton . According to

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1512-485: A second line to make six round voyages a year between Manaus and Tabatinga, and a third, two trips a month between Pará and Cametá. This was the first step in opening up the vast interior. The success of the venture called attention to the opportunities for economic exploitation of the Amazon, and a second company soon opened commerce on the Madeira, Purús, and Negro; a third established a line between Pará and Manaus, and

1638-412: A significant role in minimizing wave energy as it moves onshore. As a result, coastal dunes, especially those in the foredune area affected by a storm surge , will retreat or erode. To counteract the damage from tropical activity on coastal dunes, short term post-storm efforts can be made by individual agencies through fencing to help with sand accumulation. How much a dune erodes during any storm surge

1764-462: A star dune superimposed on its crest is the most common complex dune. Simple dunes represent a wind regime that has not changed in intensity or direction since the formation of the dune, while compound and complex dunes suggest that the intensity and direction of the wind has changed. The sand mass of dunes can move either windward or leeward, depending on if the wind is making contact with the dune from below or above its apogee. If wind hits from above,

1890-819: A unidirectional wind. In the sheltered troughs between highly developed seif dunes, barchans may be formed, because the wind is constrained to be unidirectional by the dunes. Seif dunes are common in the Sahara. They range up to 300 m (980 ft) in height and 300 km (190 mi) in length. In the southern third of the Arabian Peninsula, a vast erg , called the Rub' al Khali or Empty Quarter, contains seif dunes that stretch for almost 200 km (120 mi) and reach heights of over 300 m (980 ft). Linear loess hills known as pahas are superficially similar. These hills appear to have been formed during

2016-449: Is a landform composed of wind- or water-driven sand . It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex . A large dune complex is called a dune field , while broad, flat regions covered with wind-swept sand or dunes, with little or no vegetation, are called ergs or sand seas . Dunes occur in different shapes and sizes, but most kinds of dunes are longer on

2142-485: Is a type of sandstone that is formed when a marine or aeolian sand dune becomes compacted and hardened. Once in this form, water passing through the rock can carry and deposit minerals, which can alter the colour of the rock. Cross-bedded layers of stacks of lithified dunes can produce the cross-hatching patterns, such as those seen in Zion National Park in the western United States. A slang term, used in

2268-442: Is a very large aeolian landform, with a length of several kilometers and a height of tens to hundreds of meters, and which may have superimposed dunes. Dunes are made of sand-sized particles, and may consist of quartz, calcium carbonate, snow, gypsum, or other materials. The upwind/upstream/upcurrent side of the dune is called the stoss side; the downflow side is called the lee side. Sand is pushed (creep) or bounces ( saltation ) up

2394-410: Is blown along the beach. Dunes form where the beach is wide enough to allow for the accumulation of wind-blown sand, and where prevailing onshore winds tend to blow sand inland. The three key ingredients for coastal dune formation are a large sand supply, winds to move said sand supply, and a place for the sand supply to accumulate. Obstacles—for example, vegetation, pebbles and so on—tend to slow down

2520-445: Is by saltation , where sand particles skip along the ground like a bouncing ball . When these skipping particles land, they may knock into other particles and cause them to move as well, in a process known as creep . With slightly stronger winds, particles collide in mid-air, causing sheet flows . In a major dust storm , dunes may move tens of metres through such sheet flows. Also as in the case of snow, sand avalanches , falling down

2646-428: Is due to a number of pressures related to their proximity to the ocean and confinement to growth on sandy substrates. These include: Plants have evolved many adaptations to cope with these pressures: In deserts where large amounts of limestone mountains surround a closed basin , such as at White Sands National Park in south-central New Mexico , occasional storm runoff transports dissolved limestone and gypsum into

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2772-589: Is home to the Maranhão Babaçu forests , a tropical moist forest ecoregion dominated by the Babaçu palm. The Babaçu palm produces oil which is extracted commercially and used for a variety of purposes including food and beauty products. The southern portion of the state belong to the lower terraces of the great Brazilian Highlands , occupied by the Cerrado savannas. Several plateau escarpments , including

2898-519: Is located 13 kilometres (8.1 mi) from the center of São Luís . It began handling international flights in October 2004. It has a covered area of 8,100 square metres (87,000 sq ft) and a capacity of one million passengers per year. Renato Moreira Airport is a national airport located in Imperatriz . Infraero has administered the airport since November 3, 1980, one year before it

3024-404: Is related to its location on the coastal shoreline and the profile of the beach during a particular season. In those areas with harsher winter weather, during the summer a beach tends to take on more of a convex appearance due to gentler waves, while the same beach in the winter may take on more of a concave appearance. As a result, coastal dunes can get eroded much more quickly in the winter than in

3150-531: Is the babassu . Agribusiness , the aluminium and alumina transformation industries, the pulp industry , natural gas production , and the food and timber industries complement the state economy. The Maranhão agricultural sector stands out in the production of rice (fifth-largest rice production in the country, and highest in the Northeast), cassava (second-largest planted area in the Northeast), soybean , cotton (in both cases second-largest producer in

3276-850: Is the largest river by discharge volume of water in the world, and the longest or second-longest river system in the world , a title which is disputed with the Nile . The headwaters of the Apurímac River on Nevado Mismi had been considered for nearly a century the Amazon basin 's most distant source until a 2014 study found it to be the headwaters of the Mantaro River on the Cordillera Rumi Cruz in Peru . The Mantaro and Apurímac rivers join, and with other tributaries form

3402-522: Is the Brazilian state capital which most closely resembles a Portuguese city. By the early 20th century São Luís had about 30,000 inhabitants, and contained several convents, charitable institutes, the episcopal palace, a fine Carmelite church, and an ecclesiastical seminary. The historic city center was declared a World Heritage Site in 1997. According to the IBGE , there were 6,776,699 people residing in

3528-477: Is the largest drainage basin in the world, with an area of approximately 7,000,000 km (2,700,000 sq mi). The portion of the river's drainage basin in Brazil alone is larger than any other river's basin. The Amazon enters Brazil with only one-fifth of the flow it finally discharges into the Atlantic Ocean , yet already has a greater flow at this point than the discharge of any other river in

3654-466: Is the largest river branch one encounters when journeying upstream, and lies farther to the west than any other tributary of the Amazon. For most of the 18th–19th centuries and into the 20th century, the Marañón was generally considered the source of the Amazon. Early scientific, zoological, and botanical exploration of the Amazon River and basin took place from the 18th century through the first half of

3780-491: Is the official national language, and thus the primary language taught in schools. English and Spanish are part of the official high school curriculum. Educational institutions in Maranhão include: Maranhão is one of the poorest states of Brazil. The state has 3.4% of the Brazilian population and produces only 1.3% of the Brazilian GDP . The service sector is the largest component of GDP at 70%, followed by

3906-627: Is uncertain; the name probably originates from Portuguese settlers from Maranhão in Avis in the province of Alentejo. The word was first used to refer to the Amazon River , which is today used to refer to the Peruvian part of the river ( Marañón ). The first known European to explore Maranhão was the Spanish explorer Vicente Yáñez Pinzón in 1500, but it was granted to João de Barros in 1534 as

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4032-712: The Amazon warriors , a tribe of women warriors related to Iranian Scythians and Sarmatians mentioned in Greek mythology . The word Amazon itself may be derived from the Iranian compound * ha-maz-an- "(one) fighting together" or ethnonym * ha-mazan- "warriors", a word attested indirectly through a derivation, a denominal verb in Hesychius of Alexandria 's gloss "ἁμαζακάραν· πολεμεῖν. Πέρσαι" (" hamazakaran : 'to make war' in Persian"), where it appears together with

4158-580: The Center-West of the country. It is the second deepest port in the world. Among the main products handled in 2017 are soybeans (6,152,909 tons), corn (1,642,944 tons), fertilizers (1,536,697 tons), copper (836,062 tons), coal (636,254 tons), pig iron (505,733 t) clinker + slag (225,796 t), manganese (147,063 t), rice (89,833 t), imported liquid bulk (3,881,635 t), caustic soda (86,542 t), ethanol and LPG (150,753 t), totaling an annual turnover of 17,140,470 tons. The port of Ponta da Madeira, belonging to

4284-454: The Chapada das Mangabeiras , Serra do Tiracambu , and Serra das Alpercatas , mark the state's northern margin and the outlines of river valleys. The climate is hot, and the year is divided into a wet and dry season. Extreme humidity characterizes the wet season. The heat, however, is greatly modified on the coast by the south-east trade winds. The rivers of the state all flow northward to

4410-578: The Indo-Iranian root * kar- "make" (from which Sanskrit karma is also derived). Other scholars claim that the name is derived from the Tupi word amassona , meaning "boat destroyer". Recent geological studies suggest that for millions of years the Amazon River used to flow in the opposite direction - from east to west. Eventually the Andes Mountains formed, blocking its flow to

4536-519: The Pacific Ocean , and causing it to switch directions to its current mouth in the Atlantic Ocean . During what many archaeologists called the formative stage , Amazonian societies were deeply involved in the emergence of South America's highland agrarian systems. The trade with Andean civilizations in the terrains of the headwaters in the Andes formed an essential contribution to

4662-788: The Río Apurímac . A 2014 study by Americans James Contos and Nicolas Tripcevich in Area , a peer-reviewed journal of the Royal Geographical Society , however, identifies the most distant source of the Amazon as actually being in the Río Mantaro drainage. A variety of methods were used to compare the lengths of the Mantaro river vs. the Apurímac river from their most distant source points to their confluence, showing

4788-707: The Ucayali River , which in turn meets the Marañón River upstream of Iquitos, Peru , forming what countries other than Brazil consider to be the main stem of the Amazon. Brazilians call this section the Solimões River above its confluence with the Rio Negro forming what Brazilians call the Amazon at the Meeting of Waters ( Portuguese : Encontro das Águas ) at Manaus , the largest city on

4914-548: The Vale do Rio Doce is mainly destined for the export of iron ore brought from the Serra dos Carajás , in Pará. Between January and November 2017, 153.466 million tons were transported, and it is the national champion in moving loads. The Alumar Consortium Port transported 13.720 million tons between January and November 2017, mainly alumina. Marechal Cunha Machado International Airport

5040-523: The Western Desert of Egypt . The largest crescentic dunes on Earth, with mean crest-to-crest widths of more than three kilometres, are in China's Taklamakan Desert . Abundant barchan dunes may merge into barchanoid ridges, which then grade into linear (or slightly sinuous) transverse dunes, so called because they lie transverse, or across, the wind direction, with the wind blowing perpendicular to

5166-540: The industrial sector at 19.6%. Agriculture represents 10.4% of GDP (2015). Maranhão is the fourth-largest economy in the Northeast region and the 17th-largest in Brazil. Maranhão exports: aluminium 50%, iron 23.7%, soybean 13.1% (2002). Share of the Brazilian economy: 0.9% (2004). Maranhão is also known as the land of the palm trees, as the various species of this tree provide its major source of income. The most important of them, from an economic point of view,

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5292-568: The rubber boom it is estimated that diseases brought by immigrants, such as typhus and malaria , killed 40,000 native Amazonians. The first direct foreign trade with Manaus commenced around 1874. Local trade along the river was carried on by the English successors to the Amazonas Company—the Amazon Steam Navigation Company—as well as numerous small steamboats, belonging to companies and firms engaged in

5418-664: The slipface of the dunes—that face away from the winds—also move the dunes forward. Amazon River (Amazon–Ucayali–Tambo–Ené– Apurimac 6,400 km (4,000 mi) to 6,500 km (4,000 mi) (Period: 1971–2000)173,272.6 m /s (6,119,060 cu ft/s) (Period: 1928–1996)176,177 m /s (6,221,600 cu ft/s) (Period: 1903–2023)260,000 m /s (9,200,000 cu ft/s) The Amazon River ( UK : / ˈ æ m ə z ən / , US : / ˈ æ m ə z ɒ n / ; Spanish : Río Amazonas , Portuguese : Rio Amazonas ) in South America

5544-459: The southwest US , for consolidated and hardened sand dunes is "slickrock", a name that was introduced by pioneers of the Old West because their steel-rimmed wagon wheels could not gain traction on the rock. Sand dunes can have a negative impact on humans when they encroach on human habitats. Sand dunes move via a few different means, all of them helped along by wind. One way that dunes can move

5670-659: The stoss (upflow) side, where the sand is pushed up the dune, and have a shorter slip face in the lee side. The valley or trough between dunes is called a dune slack . Dunes are most common in desert environments, where the lack of moisture hinders the growth of vegetation that would otherwise interfere with the development of dunes. However, sand deposits are not restricted to deserts, and dunes are also found along sea shores, along streams in semiarid climates, in areas of glacial outwash , and in other areas where poorly cemented sandstone bedrock disintegrates to produce an ample supply of loose sand. Subaqueous dunes can form from

5796-604: The upper Amazon basin, especially Peru, decreed the opening of the Amazon to all countries, but they limited this to certain defined points: Tabatinga – on the Amazon; Cametá – on the Tocantins; Santarém – on the Tapajós; Borba – on the Madeira, and Manaus – on the Rio Negro. The Brazilian decree took effect on 7 September 1867. Thanks in part to the mercantile development associated with steamboat navigation coupled with

5922-671: The "Companhia de Navegação e Comércio do Amazonas" in Rio de Janeiro in 1852; in the following year it commenced operations with four small steamers, the Monarca ('Monarch'), the Cametá , the Marajó and the Rio Negro . At first, navigation was principally confined to the main river; and even in 1857 a modification of the government contract only obliged the company to a monthly service between Pará and Manaus, with steamers of 200 tons cargo capacity,

6048-587: The "Upper Amazon". The Amazon proper runs mostly through Brazil and Peru, and is part of the border between Colombia and Peru. It has a series of major tributaries in Colombia , Ecuador and Peru , some of which flow into the Marañón and Ucayali , and others directly into the Amazon proper. These include rivers Putumayo , Caquetá , Vaupés , Guainía , Morona , Pastaza , Nucuray, Urituyacu, Chambira , Tigre , Nanay , Napo , and Huallaga . At some points,

6174-623: The "land without people" in the Amazon Basin. This was done in conjunction with infrastructure projects mainly the Trans-Amazonian Highway ( Transamazônica ). The Trans-Amazonian Highway's three pioneering highways were completed within ten years but never fulfilled their promise. Large portions of the Trans-Amazonian and its accessory roads, such as BR-317 (Manaus- Porto Velho ), are derelict and impassable in

6300-518: The 19th century. The Cabanagem revolt (1835–1840) was directed against the white ruling class. It is estimated that from 30% to 40% of the population of Grão-Pará , estimated at 100,000 people, died. The population of the Brazilian portion of the Amazon basin in 1850 was perhaps 300,000, of whom about 175,000 were Europeans and 25,000 were slaves. The Brazilian Amazon's principal commercial city, Pará (now Belém), had from 10,000 to 12,000 inhabitants, including slaves. The town of Manáos, now Manaus, at

6426-538: The 20th century. Wary of foreign exploitation of the nation's resources, Brazilian governments in the 1940s set out to develop the interior, away from the seaboard where foreigners owned large tracts of land. The original architect of this expansion was president Getúlio Vargas , with the demand for rubber from the Allied forces in World War II providing funding for the drive. In the 1960s, economic exploitation of

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6552-413: The Amazon River." In March 1500, Spanish conquistador Vicente Yáñez Pinzón was the first documented European to sail up the Amazon River. Pinzón called the stream Río Santa María del Mar Dulce , later shortened to Mar Dulce , literally, sweet sea , because of its freshwater pushing out into the ocean. Another Spanish explorer, Francisco de Orellana , was the first European to travel from

6678-582: The Amazon basin was seen as a way to fuel the "economic miracle" occurring at the time. This resulted in the development of "Operation Amazon", an economic development project that brought large-scale agriculture and ranching to Amazonia. This was done through a combination of credit and fiscal incentives. However, in the 1970s the government took a new approach with the National Integration Program (PIN). A large-scale colonization program saw families from northeastern Brazil relocated to

6804-416: The Amazon in 1541, more than 3 million indigenous people lived around the Amazon. These pre-Columbian settlements created highly developed civilizations. For instance, pre-Columbian indigenous people on the island of Marajó may have developed social stratification and supported a population of 100,000 people. To achieve this level of development, the indigenous inhabitants of the Amazon rainforest altered

6930-513: The Amazon river is about 80 km longer than previously thought. Contos continued downstream to the ocean and finished the first complete descent of the Amazon river from its newly identified source (finishing November 2012), a journey repeated by two groups after the news spread. After about 700 km (430 mi), the Apurímac then joins Río Mantaro to form the Ene, which joins the Perene to form

7056-403: The Amazon will harm its biodiversity in the same way by "blocking fish-spawning runs, reducing the flows of vital oil nutrients and clearing forests". Damming the Amazon River could potentially bring about the "end of free flowing rivers" and contribute to an " ecosystem collapse " that will cause major social and environmental problems. The most distant source of the Amazon was thought to be in

7182-409: The Amazon, investigating many of its tributaries, including the Rio Negro, and covering a distance of over 10,000 km (6,200 mi). In what is currently in Brazil, Ecuador, Bolivia, Colombia, Peru, and Venezuela, several colonial and religious settlements were established along the banks of primary rivers and tributaries for trade, slaving , and evangelization among the indigenous peoples of

7308-564: The Apurímac river drainage for nearly a century. Such studies continued to be published even as recently as 1996, 2001, 2007, and 2008, where various authors identified the snowcapped 5,597 m (18,363 ft) Nevado Mismi peak, located roughly 160 km (99 mi) west of Lake Titicaca and 700 km (430 mi) southeast of Lima , as the most distant source of the river. From that point, Quebrada Carhuasanta emerges from Nevado Mismi, joins Quebrada Apacheta and soon forms Río Lloqueta which becomes Río Hornillos and eventually joins

7434-509: The Atlantic and a majority have navigable channels. The Gurupí River forms the northwestern boundary of the state, separating Maranhão from neighboring Pará. The Tocantins River forms part the state's southwestern boundary with Tocantins state. The Parnaíba River forms the eastern boundary of Maranhão, but it has one large tributary, the Balsas, entirely within the state. Other rivers in

7560-775: The Baía de Turiassu, facing which is São João Island , and the contiguous bays of São Marcos and São José, between which is the large island of São Luís . This indented shoreline is home to the Maranhão mangroves , the tallest mangrove forests in the world. The coastline east of Baía de São José is less indented and characterized by sand dunes, including the stark dune fields of the Lençóis Maranhenses National Park , as well as restinga forests that form on stabilized dunes. Chapada das Mangabeiras 804 m, at 10º 15' 45" S, 46º 00' 15" W. The etymology of Maranhão

7686-646: The French crown to found a colony on the island ( Equinoctial France ); this was done in 1612. The French were expelled by the Portuguese in 1615, and the Dutch held the island from 1641 to 1644. In 1621 Ceará, Maranhão and Pará were united and called the "Estado do Maranhao", which was separated from the southern captaincies. Very successful Indian missions were soon begun by the Jesuits , who were temporarily expelled as

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7812-537: The Northeast), sugarcane , corn and eucalyptus . Agriculture benefits from the infrastructure of railroads ( Ferrovia Carajás and Ferrovia Norte-Sul ) and ports (Itaqui and Ponta da Madeira ) and the proximity to the European and American markets. Maranhão has the second largest cattle herd in the Northeast and the 12th largest in the country, with 7.6 million animals. The state also produces natural gas in

7938-556: The Parnaíba basin, with a production of 8.4 million m per day, used in thermal power stations . Maranhão is the 6th largest producer in the country. Maranhão also has a hydroelectric plant (Estreito Hydroelectric Plant), a wind farm (in Lençóis Maranhenses ), and a thermoelectric plant ( Suzano Maranhão Thermal Power Plant ). Itaqui Port annually moves millions of tons of cargo, being an important logistics corridor for

8064-483: The Portuguese portion of the Amazon basin has remained a land largely undeveloped by agriculture and occupied by indigenous people who survived the arrival of European diseases. Four centuries after the European discovery of the Amazon river, the total cultivated area in its basin was probably less than 65 km (25 sq mi), excluding the limited and crudely cultivated areas among the mountains at its extreme headwaters. This situation changed dramatically during

8190-439: The Tambo, which joins the Urubamba River to form the Ucayali. After the confluence of Apurímac and Ucayali, the river leaves Andean terrain and is surrounded by floodplain . From this point to the confluence of the Ucayali and the Marañón, some 1,600 km (990 mi), the forested banks are just above the water and are inundated long before the river attains its maximum flood stage. The low river banks are interrupted by only

8316-551: The action of water flow ( fluvial processes) on sand or gravel beds of rivers , estuaries , and the sea-bed. Some coastal areas have one or more sets of dunes running parallel to the shoreline directly inland from the beach . In most cases, the dunes are important in protecting the land against potential ravages by storm waves from the sea . Artificial dunes are sometimes constructed to protect coastal areas. The dynamic action of wind and water can sometimes cause dunes to drift, which can have serious consequences. For example,

8442-409: The coastal environment of the sand dune vital to their species' survival. Over the course of time coastal dunes may be impacted by tropical cyclones or other intense storm activity, dependent on their location. Recent work has suggested that coastal dunes tend to evolve toward a high or low morphology depending on the growth rate of dunes relative to storm frequency. During a storm event, dunes play

8568-557: The concave sides of the dunes. These dunes form under winds that blow consistently from one direction (unimodal winds). They form separate crescents when the sand supply is comparatively small. When the sand supply is greater, they may merge into barchanoid ridges, and then transverse dunes (see below). Some types of crescentic dunes move more quickly over desert surfaces than any other type of dune. A group of dunes moved more than 100 metres per year between 1954 and 1959 in China 's Ningxia Province , and similar speeds have been recorded in

8694-405: The corridors between individual dunes. Because all dune arms are oriented in the same direction, and, the inter-dune corridors are generally swept clear of loose sand, the corridors can usually be traversed in between the trailing arms of the dune. However to cross straight over the dune by going over the trailing arms, can be very difficult. Also, traversing the nose is very difficult as well because

8820-439: The direction (s) of prevailing winds, are known as lunettes, source-bordering dunes, bourrelets and clay dunes. They may be composed of clay, silt, sand, or gypsum, eroded from the basin floor or shore, transported up the concave side of the dune, and deposited on the convex side. Examples in Australia are up to 6.5 km long, 1 km wide, and up to 50 metres high. They also occur in southern and West Africa , and in parts of

8946-473: The distance between the water line and where vegetation can grow. Coastal dunes can be classified by where they develop, or begin to take shape. Dunes are commonly grouped into either the Primary Dune Group or the Secondary Dune Group. Primary dunes gain most of their sand from the beach itself, while secondary dunes gain their sand from the primary dune. Along the Florida Panhandle, most dunes are considered to be foredunes or hummocks. Different locations around

9072-604: The dune and underlying soils . The stability of the dunes was once attributed to the vegetative cover but recent research has pointed to water as the main source of parabolic dune stability. The vegetation that covers them—grasses, shrubs, and trees—help anchor the trailing arms. In inland deserts, parabolic dunes commonly originate and extend downwind from blowouts in sand sheets only partly anchored by vegetation. They can also originate from beach sands and extend inland into vegetated areas in coastal zones and on shores of large lakes. Most parabolic dunes do not reach heights higher than

9198-513: The dunes and provide horticultural benefits, but instead spread taking land away from native species. Ammophila arenaria , known as European beachgrass, has a similar story, though it has no horticulture benefits. It has great ground coverage and, as intended, stabilized the dunes but as an unintended side effect prevented native species from thriving in those dunes. One such example is the dune field at Point Reyes, California . There are now efforts to get rid of both of these invasive species. As

9324-542: The dunes, washing humus into the slacks, and the slacks may be much more developed than the exposed tops of the dunes. It is usually in the slacks that more rare species are developed and there is a tendency for the dune slacks' soil to be waterlogged where only marsh plants can survive. In Europe these plants include: creeping willow, cotton grass, yellow iris , reeds, and rushes. As for vertebrates in European dunes, natterjack toads sometimes breed here. Dune ecosystems are extremely difficult places for plants to survive. This

9450-592: The dunes. Typically these are heather , heaths and gorses . These too are adapted to the low soil water content and have small, prickly leaves which reduce transpiration. Heather adds humus to the soil and is usually replaced by coniferous trees, which can tolerate low soil pH , caused by the accumulation and decomposition of organic matter with nitrate leaching. Coniferous forests and heathland are common climax communities for sand dune systems. Young dunes are called yellow dunes and dunes which have high humus content are called grey dunes . Leaching occurs on

9576-401: The effective winds associated with the growth and migration of both the parabolic and crescent dunes probably are the most consistent in wind direction. The grain size for these well-sorted, very fine to medium sands is about 0.06 to 0.5 mm. Parabolic dunes have loose sand and steep slopes only on their outer flanks. The inner slopes are mostly well packed and anchored by vegetation, as are

9702-561: The expedition turned back to attempt to rejoin Pizarro, the party being over 100 leagues downstream at this point. He accepted to change the purpose of the expedition to discover new lands in the name of the king of Spain, and the men built a larger boat in which to navigate downstream. After a journey of 600 km (370 mi) down the Napo River, they reached a further major confluence, at a point near modern Iquitos , and then followed

9828-461: The family Lauraceae ) are fairly common in that part of the Amazon and Pizarro probably saw some of these. The expedition reached the mouth of the Amazon on 24 August 1542, demonstrating the practical navigability of the Great River. In 1560, another Spanish conquistador , Lope de Aguirre , may have made the second descent of the Amazon. Historians are uncertain whether the river he descended

9954-658: The forest's ecology by selective cultivation and the use of fire. Scientists argue that by burning areas of the forest repeatedly, the indigenous people caused the soil to become richer in nutrients. This created dark soil areas known as terra preta de índio ("Indian dark earth"). Because of the terra preta, indigenous communities were able to make land fertile and thus sustainable for the large-scale agriculture needed to support their large populations and complex social structures. Further research has hypothesized that this practice began around 11,000 years ago. Some say that its effects on forest ecology and regional climate explain

10080-519: The geological record . All these dune shapes may occur in three forms: simple (isolated dunes of basic type), compound (larger dunes on which smaller dunes of same type form), and complex (combinations of different types). Simple dunes are basic forms with the minimum number of slipfaces that define the geometric type. Compound dunes are large dunes on which smaller dunes of similar type and slipface orientation are superimposed. Complex dunes are combinations of two or more dune types. A crescentic dune with

10206-595: The globe have dune formations unique to their given coastal profile. Coastal sand dunes can provide privacy and/or habitats to support local flora and fauna. Animals such as sand snakes, lizards, and rodents can live in coastal sand dunes, along with insects of all types. Often the vegetation of sand dunes is discussed without acknowledging the importance that coastal dunes have for animals. Further, some animals, such as foxes and feral pigs can use coastal dunes as hunting grounds to find food. Birds are also known to utilize coastal dunes as nesting grounds. All these species find

10332-408: The harsh conditions of the foredune, typically having deep roots which reach the water table , root nodules that produce nitrogen compounds, and protected stoma , reducing transpiration . Also, the deep roots bind the sand together, and the dune grows into a foredune as more sand is blown over the grasses. The grasses add nitrogen to the soil, meaning other, less hardy plants can then colonize

10458-563: The historian Sven Beckert, the region's cotton exports "doubled between 1770 and 1780, nearly doubled again by 1790, and nearly tripled once more by 1800." Maranhão did not join in the Brazilian declaration of independence of 1822, but in the following year the Portuguese were driven out by British sailor and liberator Admiral Lord Cochrane and it became part of the Empire of Brazil . For this achievement Lord Cochrane became 1st Marques of Maranhão and Governor of Maranhão Province . São Luís

10584-545: The internationally driven demand for natural rubber , the Peruvian city of Iquitos became a thriving, cosmopolitan center of commerce. Foreign companies settled in Iquitos, from where they controlled the extraction of rubber. In 1851 Iquitos had a population of 200, and by 1900 its population reached 20,000. In the 1860s, approximately 3,000 tons of rubber were being exported annually, and by 1911 annual exports had grown to 44,000 tons, representing 9.3% of Peru's exports. During

10710-486: The last ice age under permafrost conditions dominated by sparse tundra vegetation. Star dunes are pyramidal sand mounds with slipfaces on three or more arms that radiate from the high center of the mound. They tend to accumulate in areas with multidirectional wind regimes. Star dunes grow upward rather than laterally. They dominate the Grand Erg Oriental of the Sahara. In other deserts, they occur around

10836-412: The longer length of the Mantaro. Then distances from Lago Junín to several potential source points in the uppermost Mantaro river were measured, which enabled them to determine that the Cordillera Rumi Cruz was the most distant source of water in the Mantaro basin (and therefore in the entire Amazon basin). The most accurate measurement method was direct GPS measurement obtained by kayak descent of each of

10962-569: The main tributary rivers that drain into the Amazon. Since only 4% of the Amazon's hydropower potential has been developed in countries like Brazil, more damming projects are underway and hundreds more are planned. After witnessing the negative effects of environmental degradation, sedimentation, navigation and flood control caused by the Three Gorges Dam in the Yangtze River, scientists are worried that constructing more dams in

11088-521: The margins of the sand seas , particularly near topographic barriers. In the southeast Badain Jaran Desert of China, the star dunes are up to 500 metres tall and may be the tallest dunes on Earth. Oval or circular mounds that generally lack a slipface. Dome dunes are rare and occur at the far upwind margins of sand seas. Fixed crescentic dunes that form on the leeward margins of playas and river valleys in arid and semiarid regions in response to

11214-461: The mouth of the Rio Negro, had a population between 1,000 and 1,500. All the remaining villages, as far up as Tabatinga , on the Brazilian frontier of Peru, were relatively small. On 6 September 1850, Emperor Pedro II of Brazil sanctioned a law authorizing steam navigation on the Amazon and gave the Viscount of Mauá ( Irineu Evangelista de Sousa ) the task of putting it into effect. He organised

11340-581: The name ). Gonzalo Pizarro set off in 1541 to explore east of Quito into the South American interior in search of El Dorado , the "city of gold" and La Canela , the "valley of cinnamon ". He was accompanied by his second-in-command Francisco de Orellana . After 170 km (106 mi), the Coca River joined the Napo River (at a point now known as Puerto Francisco de Orellana );

11466-658: The nose is usually made up of loose sand without much if any vegetation. A type of extensive parabolic dune that lacks discernible slipfaces and has mostly coarse grained sand is known as a zibar . The term zibar comes from the Arabic word to describe "rolling transverse ridges ... with a hard surface". The dunes are small, have low relief, and can be found in many places across the planet from Wyoming (United States) to Saudi Arabia to Australia. Spacing between zibars ranges from 50 to 400 metres and they do not become more than 10 metres high. The dunes form at about ninety degrees to

11592-558: The origins of the upstream river basins, situated in the Andes , to the mouth of the river. In this journey, Orellana baptized some of the affluents of the Amazonas like Rio Negro , Napo and Jurua . The name Amazonas is thought to be taken from the native warriors that attacked this expedition, mostly women, that reminded De Orellana of the mythical female Amazon warriors from the ancient Hellenic culture in Greece (see also Origin of

11718-507: The otherwise inexplicable band of lower rainfall through the Amazon basin . Many indigenous tribes engaged in constant warfare . According to James S. Olson , "The Munduruku expansion (in the 18th century) dislocated and displaced the Kawahíb , breaking the tribe down into much smaller groups ... [Munduruku] first came to the attention of Europeans in 1770 when they began a series of widespread attacks on Brazilian settlements along

11844-427: The party stopped for a few weeks to build a boat just upriver from this confluence. They continued downriver through an uninhabited area, where they could not find food. Orellana offered and was ordered to follow the Napo River, then known as Río de la Canela ("Cinnamon River"), and return with food for the party. Based on intelligence received from a captive native chief named Delicola, they expected to find food within

11970-479: The population, and their mixing and living together. The white star in the upper left corner symbolizes Maranhão itself, and is supposed to be Beta Scorpii , as the constellation Scorpius is also depicted on the national flag of Brazil . The flag has a ratio of 2:3. This article incorporates text from the Catholic Encyclopedia , a publication now in the public domain. Dune A dune

12096-440: The prevailing wind which blows away the small, fine-grained sand leaving behind the coarser grained sand to form the crest. Occurring wherever winds periodically reverse direction, reversing dunes are varieties of any of the above shapes. These dunes typically have major and minor slipfaces oriented in opposite directions. The minor slipfaces are usually temporary, as they appear after a reverse wind and are generally destroyed when

12222-480: The rainy season. Small towns and villages are scattered across the forest, and because its vegetation is so dense, some remote areas are still unexplored. Many settlements grew along the road from Brasília to Belém with the highway and National Integration Program, however, the program failed as the settlers were unequipped to live in the delicate rainforest ecosystem. This, although the government believed it could sustain millions, instead could sustain very few. With

12348-484: The resultant direction of sand movement (hence the name "longitudinal"). Some linear dunes merge to form Y-shaped compound dunes. Formation is debated. Ralph Bagnold , in The Physics of Blown Sand and Desert Dunes , suggested that some seif dunes form when a barchan dune moves into a bidirectional wind regime, and one arm or wing of the crescent elongates. Others suggest that seif dunes are formed by vortices in

12474-479: The ridge crest. Seif dunes are linear (or slightly sinuous) dunes with two slip faces. The two slip faces make them sharp-crested. They are called seif dunes after the Arabic word for "sword". They may be more than 160 kilometres (100 miles) long, and thus easily visible in satellite images (see illustrations). Seif dunes are associated with bidirectional winds. The long axes and ridges of these dunes extend along

12600-481: The river divides into anabranches , or multiple channels, often very long, with inland and lateral channels , all connected by a complicated system of natural canals, cutting the low, flat igapó lands, which are never more than 5 m (16 ft) above low river, into many islands. From the town of Canaria at the great bend of the Amazon to the Negro, vast areas of land are submerged at high water, above which only

12726-437: The river. The Amazon River has an average discharge of about 215,000–230,000 m /s (7,600,000–8,100,000 cu ft/s)—approximately 6,591–7,570 km (1,581–1,816 cu mi) per year, greater than the next seven largest independent rivers combined. Two of the top ten rivers by discharge are tributaries of the Amazon river. The Amazon represents 20% of the global riverine discharge into oceans. The Amazon basin

12852-417: The rivers from their source points to their confluence (performed by Contos). Obtaining these measurements was difficult given the class IV–V nature of each of these rivers, especially in their lower "Abyss" sections. Ultimately, they determined that the most distant point in the Mantaro drainage is nearly 80 km farther upstream compared to Mt. Mismi in the Apurímac drainage, and thus the maximal length of

12978-494: The rubber trade, navigating the Negro, Madeira, Purús, and many other tributaries, such as the Marañón, to ports as distant as Nauta , Peru. By the turn of the 20th century, the exports of the Amazon basin were India-rubber , cacao beans , Brazil nuts and a few other products of minor importance, such as pelts and exotic forest produce ( resins , barks, woven hammocks , prized bird feathers , live animals) and extracted goods, such as lumber and gold. Since colonial times,

13104-415: The sand in the dune migrates forward. In plan view, these are U-shaped or V-shaped mounds of well-sorted, very fine to medium sand with elongated arms that extend upwind behind the central part of the dune. There are slipfaces that often occur on the outer side of the nose and on the outer slopes of the arms. These dunes often occur in semiarid areas where the precipitation is retained in the lower parts of

13230-425: The sand particles move leeward; the leeward flux of sand is greater than the windward flux. Conversely, if sand hits from below, sand particles move windward. Further, if the wind is carrying sand particles when it hits the dune, the dune's sand particles will saltate more than if the wind had hit the dune without carrying sand particles. Coastal dunes form when wet sand is deposited along the coast and dries out and

13356-438: The sea. A nabkha , or coppice dune, is a small dune anchored by vegetation. They usually indicate desertification or soil erosion, and serve as nesting and burrow sites for animals. Sub-aqueous ( underwater ) dunes form on a bed of sand or gravel under the actions of water flow. They are ubiquitous in natural channels such as rivers and estuaries, and also form in engineered canals and pipelines. Dunes move downstream as

13482-476: The second type of mounds. They are best represented by the Marajoara culture . Figurative mounds are the most recent types of occupation. There is ample evidence that the areas surrounding the Amazon River were home to complex and large-scale indigenous societies, mainly chiefdoms who developed towns and cities. Archaeologists estimate that by the time the Spanish conquistador De Orellana traveled across

13608-568: The social and religious development of higher-altitude civilizations like the Muisca and Incas . Early human settlements were typically based on low-lying hills or mounds. Shell mounds were the earliest evidence of habitation; they represent piles of human refuse (waste) and are mainly dated between 7500 BC and 4000 BC. They are associated with ceramic age cultures ; no preceramic shell mounds have been documented so far by archaeologists . Artificial earth platforms for entire villages are

13734-459: The state in 2022. The population density was 20.6 inhabitants/km. Urbanization : 68.1% (2004); Population growth : 1.5% (1991–2000); Houses : 1,442,500 (2005). The last PNAD (National Research for Sample of Domiciles) census revealed the following numbers: 4,499,018 Brown ( Multiracial ) people (66.4%), 1,361,865 White people (20.1%), 854,424 Black people (12.6%), 54,682 Amerindian people (0.8%), 6,541 Asian people (0.1%). According to

13860-849: The state include the Turiassu (or Turiaçu) which runs just east of the Gurupi, emptying into the Baía de Turiassu ; the Mearim , Pindaré , and Grajaú , which empty into the Baía de São Marcos ; and the Itapecuru and Munim which discharge into the Baía de São José . Like the Amazon, the Mearim has a pororoca or tidal bore in its lower channel, which greatly interferes with navigation. The western coastline has many small indentations, which are usually masked by islands or shoals. The largest of these are

13986-470: The state is a heavily forested plain traversed by numerous rivers, occupied by the eastern extension of the tropical moist forests of Amazonia . The Tocantins–Araguaia–Maranhão moist forests occupy the northwestern portion of the state, extending from the Pindaré River west into neighboring Pará state. The north-central and northeastern portion of the state, extending eastward into northern Piauí,

14112-402: The steeper slip face facing downstream. Ripple marks preserved in sedimentary strata in the geological record can be used to determine the direction of current flow, and thus an indication of the source of the sediments. Dunes on the bed of a channel significantly increase flow resistance, their presence and growth playing a major part in river flooding . A lithified (consolidated) sand dune

14238-604: The stoss side, and slides down the lee side. A side of a dune that the sand has slid down is called a slip face (or slipface). The Bagnold formula gives the speed at which particles can be transported. Five basic dune types are recognized: crescentic, linear, star, dome, and parabolic. Dune areas may occur in three forms: simple (isolated dunes of basic type), compound (larger dunes on which smaller dunes of same type form), and complex (combinations of different types). Barchan dunes are crescent-shaped mounds which are generally wider than they are long. The lee-side slipfaces are on

14364-679: The summer. The converse is true in areas with harsher summer weather. There are many threats to these coastal communities. Some coastal dunes, for example ones in San Francisco, have been completely altered by urbanization; reshaping the dune for human use. This puts native species at risk. Another danger, in California and places in the UK specifically, is the introduction of invasive species. Plant species, such as Carpobrotus edulis , were introduced from South Africa in an attempt to stabilize

14490-509: The town of Eucla, Western Australia , had to be relocated in the 1890s because of dune drift. The modern word "dune" came into English from French around 1790, which in turn came from Middle Dutch dūne . A universally precise distinction does not exist between ripples, dunes, and draas , which are all deposits of the same type of materials. Dunes are generally defined as greater than 7 cm tall and may have ripples, while ripples are deposits that are less than 3 cm tall. A draa

14616-517: The upper Amazon, now known as the Solimões, for a further 1,200 km (746 mi) to its confluence with the Rio Negro (near modern Manaus ), which they reached on 3 June 1542. Regarding the initial mission of finding cinnamon, Pizarro reported to the king that they had found cinnamon trees, but that they could not be profitably harvested. True cinnamon ( Cinnamomum Verum ) is not native to South America. Other related cinnamon-containing plants (of

14742-459: The upper part of the trees of the sombre forests appear. Near the mouth of the Rio Negro to Serpa, nearly opposite the river Madeira, the banks of the Amazon are low, until approaching Manaus, they rise to become rolling hills. The Lower Amazon begins where the darkly colored waters of the Rio Negro meets the sandy-colored Rio Solimões (the upper Amazon), and for over 6 km (3.7 mi) these waters run side by side without mixing . At Óbidos,

14868-471: The upstream slope is eroded and the sediment deposited on the downstream or lee slope in typical bedform construction. In the case of sub-aqueous barchan dunes, sediment is lost by their extremities, known as horns. These dunes most often form as a continuous 'train' of dunes, showing remarkable similarity in wavelength and height. The shape of a dune gives information about its formation environment. For instance, rivers produce asymmetrical ripples, with

14994-511: The vast rainforest, such as the Urarina . In the late 1600s, Czech Jesuit Father Samuel Fritz , an apostle of the Omagus established some forty mission villages. Fritz proposed that the Marañón River must be the source of the Amazon, noting on his 1707 map that the Marañón "has its source on the southern shore of a lake that is called Lauricocha , near Huánuco ." Fritz reasoned that the Marañón

15120-534: The western United States, especially Texas. U-shaped mounds of sand with convex noses trailed by elongated arms are parabolic dunes. These dunes are formed from blowout dunes where the erosion of vegetated sand leads to a U-shaped depression. The elongated arms are held in place by vegetation; the largest arm known on Earth reaches 12 km. Sometimes these dunes are called U-shaped, blowout , or hairpin dunes, and they are well known in coastal deserts. Unlike crescent shaped dunes, their crests point upwind. The bulk of

15246-402: The wind and lead to the deposition of sand grains. These small "incipient dunes or "shadow dunes" tend to grow in the vertical direction if the obstacle slowing the wind can also grow vertically (i.e., vegetation). Coastal dunes expand laterally as a result of lateral growth of coastal plants via seed or rhizome . Models of coastal dunes suggest that their final equilibrium height is related to

15372-483: The wind next blows in the dominant direction. Draas are very large-scale dune bedforms; they may be tens or a few hundreds of metres in height, kilometres wide, and hundreds of kilometres in length. After a draa has reached a certain size, it generally develops superimposed dune forms. They are thought to be more ancient and slower-moving than smaller dunes, and to form by vertical growth of existing dunes. Draas are widespread in sand seas and are well-represented in

15498-536: The world. The Amazon was initially known by Europeans as the Marañón , and the Peruvian part of the river is still known by that name, as well as the Brazilian state of Maranhão , which contains part of the Amazon. It later became known as Rio Amazonas in Spanish and Portuguese. The name Rio Amazonas was reportedly given after native warriors attacked a 16th-century expedition by Francisco de Orellana . The warriors were led by women, reminding de Orellana of

15624-465: The worst road networks in the country. Ferrovia Carajás Ferrovia Norte-Sul Ferrovia São Luís-Teresina The telephone area codes (named DDD in Brazil) for Maranhão are 98 and 99. The flag of Maranhão was designed by the poet Joaquim de Souza Andrade , and was adopted by decree nr. 6, of December 21, 1889. The colored strips (red, white and black) symbolize the different ethnic groups which make up

15750-400: Was officially opened. The passenger terminal was modified and expanded in 1998, giving it new arrival and departure areas, an expanded main concourse, and air conditioning of the entire terminal. The main highways in Maranhão are BR-010 , BR-135 , BR-316 , BR-222 and BR-226 . The state has a weak road infrastructure in the southern part of the state, and was identified, in 2022, as one of

15876-513: Was the Amazon or the Orinoco River , which runs more or less parallel to the Amazon further north. Portuguese explorer Pedro Teixeira was the first European to travel up the entire river. He arrived in Quito in 1637, and returned via the same route. From 1648 to 1652, Portuguese Brazilian bandeirante António Raposo Tavares led an expedition from São Paulo overland to the mouth of

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