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Raft
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, sealed barrels, 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, bamboo or reeds; early buoyed or float rafts use inflated animal skins or sealed clay pots which are lashed together. Modern float rafts may also use pontoons, drums, or extruded polystyrene blocks. Depending on its use and size, it may have a superstructure, masts, or rudders. Timber rafting is used by the logging industry for the transportation of logs, by tying them together into rafts and d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 part of the experience. This activity as an adventure sport has become popular since the 1950s, if not earlier, evolving from individuals paddling to rafts with double-bladed paddles or oars to multi-person rafts propelled by single-bladed paddles and steered by a person at the stern, or by the use of oars. Rafting on certain sections of rivers is considered an extreme sport and can be fatal, while other sections are not so extreme or difficult. Rafting is also a competitive sport practiced around the world which culminates in a world rafting championship event between the participating nations. The International Rafting Federation, often referred to as the IRF, is the worldwide body which oversees all aspects of the sport. Equipment ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Raft Guara
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, sealed barrels, 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, bamboo or reeds; early buoyed or float rafts use inflated animal skins or sealed clay pots which are lashed together. Modern float rafts may also use pontoons, drums, or extruded polystyrene blocks. Depending on its use and size, it may have a superstructure, masts, or rudders. Timber rafting is used by the logging industry for the transportation of logs, by tying them together into rafts and dri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 means of transporting felled timber. Both methods may be referred to as timber floating. The tradition of timber rafting cultivated in Austria, the Czech Republic, Germany, Latvia, Poland and Spain was inscribed on UNESCO Representative List of the Intangible Cultural Heritage of Humanity in 2022 Historical rafting Unlike log driving, which was a dangerous task of floating separate logs, floaters or raftsmen could enjoy relative comfort of navigation, with cabins built on rafts, steering by means of oars and possibility to make stops. On the other hand, rafting requires wider waterflows. Timber rafts were also used as a means of transportation of people and goods, both raw materials ( ore, fur, game) and man-made. Theophrastus (''Hist. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Whitewater
Whitewater forms in the context of rapids, in particular, when a river's Stream gradient, gradient changes enough to generate so much turbulence that air is trapped within the water. This forms an unstable current that foam, froths, making the water appear opaque and white. The term "whitewater" also has a broader meaning, applying to any river or creek that has a significant number of rapids. The term is also used as an adjective describing boating on such rivers, such as whitewater canoeing or whitewater kayaking. Fast rivers Four factors, separately or in combination, can create rapids: gradient, constriction, obstruction, and flow rate. Gradient, constriction, and obstruction are streambed topography factors and are relatively consistent. Flow rate is dependent upon both seasonal variation in precipitation and snowmelt and upon release rates of upstream dams. Streambed topography Streambed topography is the primary factor in creating rapids, and is generally consist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oceanic Dispersal
Oceanic dispersal is a type of biological dispersal that occurs when Terrestrial animal, 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 islands, as opposed to a single journey directly to the destination. Often this occurs via large rafts of floating vegetation such as are sometimes seen floating down major rivers in the tropics and washing out to sea, occasionally with animals trapped on them. Dispersal via such a raft is sometimes referred to as a rafting event. Colonization of land masses by plants can also occur via long-distance oceanic dispersal of floating seeds. History Rafting has played an important role in the colonization of isolated land masses by mammals. Prominent examples include Madagascar, which has been isolated for ~120 million years (Year#SI prefix multipliers, Ma), and South America, which was isolated for much of the Cenozoic. Both lan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Float (nautical)
A float (also called a pontoon) is an airtight hollow structure, similar to a pressure vessel, designed to provide buoyancy in water. Its principal applications are in hull (watercraft), watercraft hulls, Floatplane, aircraft floats, Floating dock (jetty), floating piers, aquaculture, pontoon bridge, pontoon bridges, and marine engineering applications such as marine salvage, salvage. Applications Floats make up the multipart hulls of catamarans and trimarans and provide buoyancy for floatplanes, seaplanes and houseboats. They are used in pontoon bridges, floating piers, and floats anchored to the seabed for recreation or dockage. They are also used in shipbuilding and marine salvage, often deployed uninflated then pressurized to raise a sunken object. In military, floats are used as pontoon bridges or transportation platforms for heavier vehicles or machinery. In popular usage, the term ''pontoon'' can refer to any of several of the following objects that make use of nautical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Balsa
''Ochroma pyramidale'', commonly known as balsa, is a large, fast-growing tree native to the Americas. It is the sole member of the genus ''Ochroma'', and is classified in the subfamily Bombacoideae of the mallow family Malvaceae. The tree is famous for its wide usage in woodworking, due to its softness and its high strength compared to its low density. The name ''balsa'' is the Spanish word for "raft" and the Portuguese word for ferry. A deciduous angiosperm, ''Ochroma pyramidale'' can grow up to 30 m tall, and is classified as a hardwood despite the wood itself being very soft; it is the softest commercial hardwood and is widely used because of its light weight. Balsa trees grow extremely fast, often up to 27 metres in 10–15 years, and do not usually live beyond 30 to 40 years. In terms of volume (as opposed to height) they may be the fastest growing tree known; Streets mentions one individual which grew tall and diameter at breast height during a period of fifteen mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tsunami
A tsunami ( ; from , ) 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 underwater explosions (including detonations, landslides, glacier calvings, meteorite impacts and other disturbances) above or below water all have the potential to generate a tsunami. Unlike normal ocean waves, which are generated by wind, or tides, which are in turn generated by the gravitational pull of the Moon and the Sun, a tsunami is generated by the displacement of water from a large event. Tsunami waves do not resemble normal undersea currents or sea waves because their wavelength is far longer. Rather than appearing as a breaking wave, a tsunami may instead initially resemble a rapidly rising tide. For this reason, it is often referred to as a tidal wave, although this usage is not favoured by the scientific community because it might give the false impression of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the 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 tables can be used for any given locale to find the predicted times and amplitude (or " tidal range"). The predictions are influenced by many factors including the alignment of the Sun and Moon, the phase and amplitude of the tide (pattern of tides in the deep ocean), the amphidromic systems of the oceans, and the shape of the coastline and near-shore bathymetry (see '' Timing''). They are however only predictions, the actual time and height of the tide is affected by wind and atmospheric pressure. Many shorelines experience semi-diurnal tides—two nearly equal high and low tides each day. Other locations have a diurnal tide—one high and low tide each day. A "mixed tide"—two uneven magnitude tides a day—is a third regular category. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earthquake
An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they cannot be felt, to those violent enough to propel objects and people into the air, damage critical infrastructure, and wreak destruction across entire cities. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume. In its most general sense, the word ''earthquake'' is used to describe any seismic event that generates seismic waves. Earthquakes can occur naturally or be induced by human activities, such as mining, fracking, and nuclear weapons testing. The initial point of rupture is called the hypocenter or focus, while the ground level directly above it is the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Buoyancy
Buoyancy (), or upthrust, is the force exerted by a fluid opposing the weight of a partially or fully immersed object (which may be also be a parcel of fluid). In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus, the pressure at the bottom of a column of fluid is greater than at the top of the column. Similarly, the pressure at the bottom of an object submerged in a fluid is greater than at the top of the object. The pressure difference results in a net upward force on the object. The magnitude of the force is proportional to the pressure difference, and (as explained by Archimedes' principle) is equivalent to the weight of the fluid that would otherwise occupy the submerged volume of the object, i.e. the Displacement (fluid), displaced fluid. For this reason, an object with average density greater than the surrounding fluid tends to sink because its weight is greater than the weight of the fluid it displaces. If the objec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flotsam And Jetsam
In maritime law, flotsam'','' jetsam'','' lagan'','' and derelict are terms for various types of property lost or abandoned at sea. The words have specific nautical meanings, with legal consequences in the law of admiralty and marine salvage. A shipwreck is defined as the remains of a ship that has been wrecked, whether it has sunk or is floating on the surface of the water. Overview A wreck is categorized as property belonging to no apparent owner that either sinks to the seabed or floats on the surface of the water, whether it be intentionally cast overboard or as the result of an accident. The term encompasses the hull of the vessel and its fixtures as well as any other form of object on board, such as cargo and stores, and personal effects of the crew and passengers. This also encompasses the narrower definition of salvage, that is, property that has been recovered from a wreckage, or the recovery of the ship itself. There are a number of factors that contribute to the for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
