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A raft is any flat structure for support or transportation over water. It is usually of basic design, characterized by the absence of a hull. Rafts are usually kept afloat by using any combination of buoyant materials such as
wood Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin th ...
, sealed
barrel A barrel or cask is a hollow cylindrical container with a bulging center, longer than it is wide. They are traditionally made of wooden staves and bound by wooden or metal hoops. The word vat is often used for large containers for liquids, ...
s, or inflated air chambers (such as pontoons), and are typically not propelled by an engine. Rafts are an ancient mode of transport; naturally-occurring rafts such as entwined vegetation and pieces of wood have been used to traverse water since the dawn of humanity.


Human-made rafts

Traditional or primitive rafts were constructed of wood or reeds. Modern rafts may also use pontoons,
drums A drum kit (also called a drum set, trap set, or simply drums) is a collection of drums, cymbals, and other Percussion instrument, auxiliary percussion instruments set up to be played by one person. The player (drummer) typically holds a pair o ...
, or
extruded polystyrene Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a ...
blocks. Inflatable rafts up to the 20th century used flotation chambers made of goat- or buffalo-skins, but most now use durable, multi-layered rubberized fabrics. Depending on its use and size, it may have a
superstructure A superstructure is an upward extension of an existing structure above a baseline. This term is applied to various kinds of physical structures such as buildings, bridges, or ships. Aboard ships and large boats On water craft, the superstruct ...
, masts, or rudders.
Timber rafting Timber rafting is a method of transporting felled tree trunks by tying them together to make rafts, which are then drifted or pulled downriver, or across a lake or other body of water. It is arguably, after log driving, the second cheapest mean ...
is used by the
logging Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidding, on-site processing, and loading of trees or logs onto trucks or skeleton cars. Logging is the beginning of a supply chain ...
industry for the transportation of logs, by tying them together into rafts and drifting or pulling them down a river. This method was very common up until the middle of the 20th century but is now used only rarely. Large rafts made of
balsa ''Ochroma pyramidale'', commonly known as the balsa tree, is a large, fast-growing tree native to the Americas. It is the sole member of the genus ''Ochroma''. The tree is famous for its wide usage in woodworking, with the name ''balsa'' being ...
logs and using sails for navigation were important in maritime trade on the Pacific Ocean coast of South America from pre-Columbian times until the 19th century. Voyages were made to locations as far away as Mexico, and many trans-Pacific voyages using replicas of ancient rafts have been undertaken to demonstrate possible contacts between South America and
Polynesia Polynesia () "many" and νῆσος () "island"), to, Polinisia; mi, Porinihia; haw, Polenekia; fj, Polinisia; sm, Polenisia; rar, Porinetia; ty, Pōrīnetia; tvl, Polenisia; tkl, Polenihia (, ) is a subregion of Oceania, made up of ...
.Smith, Cameron M. and Haslett, John F. (1999), "Construction and Sailing Characteristics of a Pre-Columbian Raft Replica", ''Bulletin of Primitive Technology'', pp. 13–18 The type of raft used for recreational
rafting Rafting and whitewater rafting are recreational outdoor activities which use an inflatable raft to navigate a river or other body of water. This is often done on whitewater or different degrees of rough water. Dealing with risk is often a ...
is almost exclusively an
inflatable raft An inflatable is an object that can be inflated with a gas, usually with air, but hydrogen, helium and nitrogen are also used. One of several advantages of an inflatable is that it can be stored in a small space when not inflated, since inflata ...
, manufactured of flexible materials for use on
whitewater Whitewater forms in a rapid context, in particular, when a river's gradient changes enough to generate so much turbulence that air is trapped within the water. This forms an unstable current that froths, making the water appear opaque and ...
.


Natural rafts

In
biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...
, particularly in
island biogeography Insular biogeography or island biogeography is a field within biogeography that examines the factors that affect the species richness and diversification of isolated natural communities. The theory was originally developed to explain the pattern of ...
, non-manmade rafts are an important concept. Such rafts consist of matted clumps of
vegetation Vegetation is an assemblage of plant species and the ground cover they provide. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic character ...
that has been swept off the dry land by a
storm A storm is any disturbed state of the natural environment or the atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmos ...
,
tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explo ...
,
tide Tides are the rise and fall of sea levels caused by the combined effects of the gravity, gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide t ...
,
earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...
or similar event; in modern times they sometimes also incorporate other kind of
flotsam and jetsam In maritime law, flotsam'','' jetsam'','' lagan'','' and derelict are specific kinds of shipwreck. The words have specific nautical meanings, with legal consequences in the law of admiralty and marine salvage. A shipwreck is defined as the r ...
, e.g. plastic containers. They stay afloat by its natural
buoyancy Buoyancy (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the p ...
and can travel for hundreds, even thousands of miles and are ultimately destroyed by
wave In physics, mathematics, and related fields, a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities. Waves can be periodic, in which case those quantities oscillate repeatedly about an equilibrium (res ...
action and
decomposition Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is e ...
, or make landfall. Rafting events are important means of
oceanic dispersal Oceanic dispersal is a type of biological dispersal that occurs when terrestrial organisms transfer from one land mass to another by way of a sea crossing. Island hopping is the crossing of an ocean by a series of shorter journeys between island ...
for non-flying animals. For small
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
s,
amphibia Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arbore ...
ns and
reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...
s in particular, but for many
invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s as well, such rafts of vegetation are often the only means by which they could reach and – if they are lucky – colonize
ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...
ic
island An island (or isle) is an isolated piece of habitat that is surrounded by a dramatically different habitat, such as water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An island ...
s before
human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
-built vehicles provided another
mode of transport Mode of transport is a term used to distinguish between different ways of transportation or transporting people or goods. The different modes of transport are air, water, and land transport, which includes rails or railways, road and off-road t ...
.


Image gallery


See also

*
Floating island A floating island is a mass of floating aquatic plants, mud, and peat ranging in thickness from several centimeters to a few meters. Floating islands are a common natural phenomenon that are found in many parts of the world. They exist less co ...
*
Great Raft The Great Raft was a gigantic log jam or series of "rafts" that clogged the Red and Atchafalaya rivers and was unique in North America in terms of its scale. Origin The Great Raft probably began forming in the 12th century. It grew from its u ...
*
Kon-Tiki The ''Kon-Tiki'' expedition was a 1947 journey by raft across the Pacific Ocean from South America to the Polynesian islands, led by Norwegian explorer and writer Thor Heyerdahl. The raft was named ''Kon-Tiki'' after the Inca god Viracocha, for ...
* L’Égaré II * La Balsa and Las Balsas *
Lifeboat Lifeboat may refer to: Rescue vessels * Lifeboat (shipboard), a small craft aboard a ship to allow for emergency escape * Lifeboat (rescue), a boat designed for sea rescues * Airborne lifeboat, an air-dropped boat used to save downed airmen ...
*
Pre-Columbian rafts Pre-Columbian rafts plied the Pacific Coast of South America for trade from about 100 BCE, and possibly much earlier. The 16th century descriptions by the Spanish of the rafts used by Native Americans along the seacoasts of Peru and Ecuador has ...
*
Pumice raft A pumice raft is a floating raft of pumice created by some eruptions of submarine volcanoes or coastal subaerial volcanoes. Biologists suggest that animals and plants have migrated from island to island on pumice rafts. Pumice rafts have uniqu ...
* ''
The Raft of the Medusa ''The Raft of the Medusa'' (french: Le Radeau de la Méduse ) – originally titled ''Scène de Naufrage'' (''Shipwreck Scene'') – is an oil painting of 1818–19 by the French Romantic painter and lithographer Théodore Géricault (1791 ...
'' *
Thor Heyerdahl Thor Heyerdahl KStJ (; 6 October 1914 – 18 April 2002) was a Norwegian adventurer and ethnographer with a background in zoology, botany and geography. Heyerdahl is notable for his ''Kon-Tiki'' expedition in 1947, in which he sailed 8,000&nb ...
*
Poon Lim Poon Lim BEM (; 8 March 1918 – 4 January 1991) was a Chinese sailor who survived 133 days alone in the South Atlantic. Lim worked as second steward on , a British merchant ship that was sunk by , a German U-boat, on 23 November 194 ...


References


External links


Rafting on the Drina River (1951) - BH Film - Official chanalWorld of Boats (EISCA) Collection ~ Australian Reed RaftWorld of Boats (EISCA) Collection ~ Brazilian JangadaHomemade Raft Plans and Photos of RaftsNeutrino Raft – vessels made from scrapTypes of Whitewater Rafts
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