Misplaced Pages

#874125

47-508: This rare phenomenon ends up forming an immense natural island, roughly the Guyana Shield , and thus technically the world's second largest, after Greenland , despite there not being a consensus on its island status. The name Casiquiare , first used in that form by Manuel Román, likely derives from the Ye'kuana language name of the river, Kashishiwadi . The first European to describe it

94-470: A tumpline and one on the back ( strangulated hernia was a common cause of death). To allow regular rests the voyageur would drop his pack at a pose about every 1 kilometre ( 1 ⁄ 2  mi) and go back for the next load. The time for a portage was estimated at one hour per half mile. The Diolkos was a paved trackway in Ancient Greece which enabled boats to be moved overland across

141-699: A Ramsar Wetland, thus becoming a protected area of international importance in accordance to the Ramsar Convention . According to recent researches, although ecosystems of the Guayana Highlands remain vibrant, emerging issues (including "a well-known invasive plant elsewhere" Poa annua and "one of the most aggressive weeds" Polypogon elongatus ) and infectious faecal bacteria Helicobacter pylori have been documented. Portage Portage or portaging ( CA : / p ɔːr ˈ t ɑː ʒ / ; US : / ˈ p ɔːr t ɪ dʒ / )

188-406: A few places iron-plated wooden rails were laid to take a handcart. Heavily used routes sometimes evolved into roads when sledges, rollers or oxen were used, as at Methye Portage . Sometimes railways ( Champlain and St. Lawrence Railroad ) or canals were built. When going downstream through rapids an experienced voyageur called the guide would inspect the rapids and choose between the heavy work of

235-654: A portage across the Thracian Chersonese is lacking, but it is possible that traces of it have been confused with traces of the Long Wall , which was restored by Justinian I in the 6th century. The region also saw extensive damage during the Gallipoli Campaign of 1915. The Skagerak always has been treacherous for shipping and early navigators tried to avoid it. There are various river systems in (modern) northern Germany and southern Denmark where

282-406: A portage and the life-threatening risk of running the rapids. If the second course were chosen, the boat would be controlled by the avant standing in front with a long paddle and the gouvernail standing in the back with a 2.7-metre (9 ft) steering paddle. The avant had a better view and was in charge but the gouvernail had more control over the boat. The other canoemen provided power under

329-728: Is a 1.7 billion-year-old Precambrian geological formation in northeast South America that forms a portion of the northern coast. The higher elevations on the shield are called the Guiana Highlands , which is where the table-like mountains called tepuis are found. The Guiana Highlands are also the source of some of the world's most well-known waterfalls such as Angel Falls , Kaieteur Falls and Cuquenan Falls . The Guiana Shield underlies Guyana (previously British Guiana ), Suriname (previously Dutch Guiana ), and French Guiana (or Guyane ), much of southern Venezuela , as well as parts of Colombia and Brazil . The rocks of

376-717: Is a common place name in Scotland and Ireland indicating the site of a portage. Portages played an important role in the economy of some African societies. For instance, Bamako was chosen as the capital of Mali because it is located on the Niger River near the rapids that divide the Upper and Middle Niger Valleys. Places where portaging occurred often became temporary and then permanent settlements. The importance of free passage through portages found them included in laws and treaties. One historically important fur trade portage

423-493: Is equally rich and 13,367 species of vascular plants have been found, approximately 40% of which is considered endemic. The shield is overlain by the largest expanse of tropical forest on any Precambrian shield area in the world. Guianan rain forest is similar in nature to Amazonian rain forest and known protected areas include the Iwokrama Forest of central Guyana, Kaieteur, Kanuku National Park of southern Guyana,

470-631: Is now Grand Portage National Monument . Recreational canoeing routes often include portages between lakes, for example, the Seven Carries route in Adirondack Park . Numerous portages were upgraded to carriageways and railways due to their economic importance. The Niagara Portage had a gravity railway in the 1760s. The passage between the Chicago and Des Plaines Rivers was through a short swamp portage which seasonally flooded and it

517-699: Is now Russia were vital for the Varangian commerce with the Orient and Byzantium . At the most important portages (such as Gnezdovo ) there were trade outposts inhabited by a mixture of Norse merchants and native population. The Khazars built the fortress of Sarkel to guard a key portage between the Volga and the Don. After Varangian and Khazar power in Eastern Europe waned, Slavic merchants continued to use

SECTION 10

#1732769296875

564-527: Is said to have a second connection with the Rio Negro by a branch, which it throws off to the westward, called the Itinivini , which leaves it at a point about 80 kilometres (50 mi) above its mouth. In the dry season, it has shallows, and is obstructed by sandbanks, a few rapids and granite rocks. Its shores are densely wooded, and the soil more fertile than that along the Rio Negro. The general slope of

611-533: Is small in comparison to what it accumulates in its course. Nevertheless, the geological processes are ongoing, and evidence points to a slow and gradual increase in the size of Casiquiare. It is likely that stream capture is in progress, i.e. what currently is the uppermost Orinoco basin, including Cunucunuma River , eventually will be entirely diverted by the Casiquiare into the Amazon basin. In flood time, it

658-704: Is the highest summit of the larger Neblina massif , a highly eroded sandstone plateau that straddles the Venezuela-Brazil border and that has lost the typical tabletop shape of the other tepuis in the region. The Guiana Shield is one of the regions of highest biodiversity in the world, and has many endemic species. The region houses over 3000 vertebrate species: 1168 fresh water fish, 269 amphibians (54% endemics), 295 reptiles (29%), 1004 birds (7.7%), and 282 mammals (11%). Diversity of invertebrates remains largely undocumented, but there are several species of endemic butterflies and dung beetles. Plant life

705-770: Is the practice of carrying water craft or cargo over land, either around an obstacle in a river, or between two bodies of water. A path where items are regularly carried between bodies of water is also called a portage. The term comes from French, where porter means "to carry", as in "portable". In Canada , the term "carrying-place" was sometimes used. Early French explorers in New France and French Louisiana encountered many rapids and cascades . The Native Americans carried their canoes over land to avoid river obstacles. Over time, important portages were sometimes provided with canals with locks , and even portage railways . Primitive portaging generally involves carrying

752-565: Is thought that a channel gradually developed unintentionally from the dragging of the boat bottoms. The 1835 Champlain and St. Lawrence Railroad connected the cities of New York and Montreal without needing to go through the Atlantic. Many settlements in North America were named for being on a portage. Portages existed in a number of locations where an isthmus existed that the local Māori could drag or carry their waka across from

799-635: The 14-kilometre ( 8 + 1 ⁄ 2  mi) Grand Portage (both in North America) often covering hilly or difficult terrain. Some portages involve very little elevation change, such as the very short Mavis Grind in Shetland , which crosses an isthmus . This section deals mostly with the heavy freight canoes used by the Canadian Voyageurs . Portage trails usually began as animal tracks and were improved by tramping or blazing. In

846-544: The Caribbean ; the Amazon Basin flows east into the western Atlantic in the extreme northeast of Brazil .) Essentially the river divide is a west-flowing, upriver section of Venezuela's Orinoco River with an outflow to the south into the Amazon Basin. This named outflow is the Casiquiare canal, which, as it heads downstream (southerly), picks up speed and also accumulates water volume. The greatest manifestation of

893-635: The Isthmus of Corinth between the Gulf of Corinth and the Saronic Gulf . It was constructed to transport high ranking Despots to conduct business in the justice system. The 6-to-8.5-kilometre-long ( 3 + 1 ⁄ 2 – 5 + 1 ⁄ 2  mi) roadway was a rudimentary form of railway , and operated from around 600 BC until the middle of the 1st century AD. The scale on which the Diolkos combined

940-677: The Tasman Sea to the Pacific Ocean or vice versa. The most famous ones are located in Auckland , where there remain three roads named 'Portage Road's in separate parts of the city. Portage Road in the Auckland suburb of Otahuhu has historical plaques at both the north and south ends proclaiming it to be 'at half a mile in length, surely the shortest road between two seas'. The small Marlborough Sounds settlement of Portage lies on

987-597: The Amazon at Manaus. It was the first expedition to use aerial photography and shortwave radio for mapping of the region. In 1968 the Casiquiare was navigated by an SRN6 hovercraft during a National Geographic expedition. The origin of the Casiquiare, at the River Orinoco, is 14 kilometres (9 mi) below the mission of La Esmeralda at 3°8′18.5″N 65°52′42.5″W  /  3.138472°N 65.878472°W  / 3.138472; -65.878472 , and about 123 metres (404 ft) above sea level. Its mouth at

SECTION 20

#1732769296875

1034-534: The Casiquiare canal, and afterwards retraced his route to the Orinoco. Along the way, he made first contact with the Ye'kuana people, whom he enlisted to help in his journey. Charles Marie de La Condamine , seven months later, was able to give to the Académie française an account of Father Román's voyage, and thus confirm the existence of this waterway, first reported by Father Acuña in 1639. Little credence

1081-468: The Guiana Shield consist of metasediments and metavolcanics ( greenstones ) overlain by sub-horizontal layers of sandstones , quartzites , shales and conglomerates intruded by sills of younger mafic intrusives such as gabbros . The oldest rocks in the shield consist of Archean Imataca Complex, composed of a quartz - feldspar gneiss and subordinate mafic gneiss. The Guri Fault marks

1128-643: The Guiana Shield: The north-central part of the Guiana Highlands is dominated by high flat-topped peaks called tepuis , of the Roraima supergroup and Quasi-Roraima formation, and the rounded granite peaks of the Parguaza and Imataca complexes to the north and southwestern edges of the area. The highest point in the shield is Pico da Neblina in Brazil at 2,995 metres (9,826 ft). Pico da Neblina

1175-527: The Orinoco and Amazon basins, called the isthmus of Pimichin , which is reached by ascending the Temi branch of the Atabapo River , an affluent of the Orinoco. Although the Temi is somewhat obstructed, it is believed that it could easily be made navigable for small craft. The isthmus is 10 miles (16 km) across, with undulating ground, nowhere over 15 metres (50 ft) high, with swamps and marshes. In

1222-508: The Rio Negro, an affluent of the Amazon River , is near the town of San Carlos and is 91 metres (299 ft) above sea level. The general course is south-west, and its length, including windings, is about 320 kilometres (200 mi). Its width, at its bifurcation with the Orinoco, is approximately 90 metres (300 ft), with a current towards the Rio Negro of 0.3 metres per second (0.75 mph). However, as it gains in volume from

1269-860: The UNESCO World Heritage Site Central Suriname Nature Reserve of Suriname , the Guiana Amazonian Park in French Guiana and the Tumucumaque National Park in the Amapá State of Brazil . In Venezuela the forests are protected by Canaima , Parima-Tapirapeco and Serranía de la Neblina national parks. In 2014, the Government of Colombia designated a 250 hectare area of the Guiana Shield, as

1316-541: The canal" is turned into a region, and an entire strip along the southern bank of the Orinoco River. Guiana Shield The Guiana Shield ( French : Plateau des Guyanes, Bouclier guyanais ; Dutch : Hoogland van Guyana, Guianaschild ; Portuguese : Planalto das Guianas, Escudo das Guianas ; Spanish : Escudo guayanés ) is one of the three cratons of the South American Plate . It

1363-607: The customs house at Abydos . It would have been too costly to regularly move large ships across the peninsula, but Cosmas says that Constantine IV did it, presumably during the blockade of Constantinople (670/1–676/7) when the Sea of Marmara and the Dardanelles were controlled by the Umayyads . Constantine is said to have "driven" the ships rather than dragged them, probably indicating the use of wheels. Archaeological evidence for

1410-414: The divide is during floods. During flood stage, the Casiquiare's main outflow point into the Rio Negro is supplemented by an overflow that is a second, and more minor, entry river bifurcation into the Rio Negro and upstream from its major, common low-water entry confluence with the Rio Negro. At flood, the river becomes an area flow source, far more than a narrow confined river. The Casiquiare canal connects

1457-685: The early 20th century, it was much used for the transit of large canoes, which were hauled across it from the Temi River and reached the Rio Negro by a little stream called the Pimichin. The Casiquiare canal – Orinoco River hydrographic divide is a representation of the hydrographic water divide that delineates the separation between the Orinoco Basin and the Amazon Basin . (The Orinoco Basin flows west–north–northeast into

Casiquiare canal - Misplaced Pages Continue

1504-470: The harbor of Alexandria , which may have been located at the southern tip of the island of Pharos. Another diolkos is mentioned by Ptolemy (90–168 CE) in his book on geography (IV, 5, 10) as connecting a false mouth of a partly silted up Nile branch with the Mediterranean Sea . Writing in the first half of the eighth century, Cosmas of Jerusalem describes the portage of boats across

1551-456: The instructions of the avant. Going upstream was more difficult, as there were many places where the current was too swift to paddle. Where the river bottom was shallow and firm, voyageurs would stand in the canoe and push it upstream with 3-metre (10 ft) poles. If the shoreline was reasonably clear the canoe could be 'tracked' or 'lined', that is, the canoemen would pull the canoe on a rope while one man stayed on board to keep it away from

1598-645: The narrowest part of the Thracian Chersonese (Gallipoli Peninsula) between the Aegean Sea and the Sea of Marmara . The peninsula there is six miles wide. Cosmas describes the dragging of small boats as common in his day for local trade between Thrace and Gothograecia . The motivation for this practice was to avoid the long detour around the peninsula and through the Dardanelles , but also to avoid

1645-473: The plains through which the canal runs is south-west, but those of the Rio Negro slope south-east. The Casiquiare is not a sluggish canal on a flat tableland, but a great, rapid river which, if its upper waters had not found contact with the Orinoco, perhaps by cutting back, would belong entirely to the Negro branch of the Amazon. To the west of the Casiquiare, there is a much shorter and easier portage between

1692-678: The portages along the Volga trade route and the Dnieper trade route . The names of the towns Volokolamsk and Vyshny Volochek may be translated as "the portage on the Lama River " and "the little upper portage", respectively (from Russian волок volok , meaning "portage", derived from the verb волочить voločitʹ "to drag"). In the 16th century, the Russians used river portages to get to Siberia (see Cherdyn Road ). Tarbert

1739-580: The shore. (The most extreme case of tracking was in the Three Gorges in China where all boats had to be pulled upstream against the current of the Yangtze River .) In worse conditions, the 'demi-chargé' technique was used. Half the cargo was unloaded, the canoe forced upstream, unloaded and then returned downstream to pick up the remaining half of the cargo. In still worse currents, the entire cargo

1786-597: The smallest watercraft, was at least once used by the Venetian Republic for the transport of a military fleet in 1439. The land link is now somewhat harder because of the disappearance of Loppio Lake. In the 8th, 9th and 10th centuries, Viking merchant-adventurers exploited a network of waterways in Eastern Europe , with portages connecting the four most important rivers of the region: Volga , Western Dvina , Dnieper , and Don . The portages of what

1833-533: The southern boundary of the complex. South of that fault are Early Proterozoic rocks consisting of the metavolcanic Pastora Supergroup and the granitic plutonic Supamo Complex. The Cuchivero Group consists of ash flow tuff and granitic plutonic rocks. The Early to Middle Proterozoic Roraima Group consists of continental clastic sedimentary rocks. These Precambrian sediments include quartz sandstones , quartzites , and conglomerates presumed to be 1.8 to 1.4 Ga in age. There are three upland areas of

1880-473: The two principles of the railway and the overland transport of ships was unique in antiquity . There is scant literary evidence for two more ship trackways referred to as diolkoi in antiquity, both located in Roman Egypt : The physician Oribasius ( c.  320–400 CE ) records two passages from his first-century colleague Xenocrates , in which the latter casually refers to a diolkos close to

1927-494: The upper Orinoco, 14 kilometres (9 mi) below the mission of Esmeraldas, with the Rio Negro affluent of the Amazon River near the town of San Carlos. The simplest description (besides the entire area-floodplain) of the water divide is a "south-bank Orinoco River strip" at the exit point of the Orinoco, also the origin of the Casiquiare canal. However, during the Orinoco's flood stage, that single, simply defined "origin of

Casiquiare canal - Misplaced Pages Continue

1974-399: The very numerous tributary streams, large and small, that it receives en route, its velocity increases, and in the wet season reaches 2.2 metres per second (5 mph), even 3.6 metres per second (8 mph) in certain stretches. It broadens considerably as it approaches its mouth, where it is about 533 metres (1,750 ft) wide. The volume of water the Casiquiare captures from the Orinoco

2021-429: The vessel and its contents across the portage in multiple trips. Small canoes can be portaged by carrying them inverted over one's shoulders and the center strut may be designed in the style of a yoke to facilitate this. Historically, voyageurs often employed tump lines on their heads to carry loads on their backs. Portages can be many kilometers in length, such as the 19-kilometre (12 mi) Methye Portage and

2068-701: The watershed is narrow and low, such as between the Treene (discharging into the North Sea) and the Schlei (discharging into the Baltic) that would have allowed portage. There is no certain physical or written evidence, except that it is known that goods were transported along these routes between different merchant settlements. The land link between Adige River and Garda Lake in Northern Italy , hardly used by

2115-646: Was Spanish Jesuit missionary and explorer Cristóbal Diatristán de Acuña in 1639. In 1744 a Jesuit priest named Manuel Román, while ascending the Orinoco River in the region of La Esmeralda , met some Portuguese slave-traders from the settlements on the Rio Negro . The Portuguese insisted they were not in Spanish territory but on a tributary of the Amazon; they invited Román back with them to prove their claim. He accompanied them on their return, by way of

2162-494: Was given to Román's statement until it was verified, in 1756, by the Spanish Boundary-line Commission of José Yturriaga and Solano . In 1800 German scientist Alexander von Humboldt and French botanist Aimé Bonpland explored the river. During a 1924–25 expedition, Alexander H. Rice Jr. of Harvard University traveled up the Orinoco, traversed the Casiquiare canal, and descended the Rio Negro to

2209-414: Was unloaded ('décharge') and carried overland while the canoe was forced upstream. In the worst case a full portage was necessary. The canoe was carried overland by two or four men (the heavier York boats had to be dragged overland on rollers) The cargo was divided into standard 41-kilogram (90 lb) packs or pièces with each man responsible for about six. One portage or canoe pack would be carried by

#874125