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bicycle, often called a bike [2] (and sometimes referred to as a "pushbike",[3] "pedal bike",[4] "pedal cycle",[5] or "cycle"[6]), is a human-powered, pedal-driven, singletrack vehicle, having two wheels attached to a frame, one behind the other. [7] A bicycle rider is called a cyclist, or bicyclist. Bicycles were introduced in the 19th century in Europe and now number
more than a billion worldwide, twice as many as automobiles.[8] They are the principal means of transportation in many regions. They also provide a popular form of recreation, and have been adapted for use as children's toys, general fitness, military and police applications, courier services, and bicycle racing. The basic shape and configuration of a typical upright, or safety bicycle, has changed little since the first chain(Continued on page 3)
driven model was developed around 1885.[9] But many details have been improved, especially since the advent of modern materials and computeraided design. These have allowed for a pro-
liferation of specialized designs for many types of cycling. The bicycle's invention has had an enormous effect on society, both in terms of culture and of advancing modern industrial meth-
ods. Several components that eventually played a key role in the development of the automobile were invented for the bicycle, including ball bearings, pneumatic tires, chain-driven
sprockets, and tension-spoked wheels.
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beach is a landform along the shoreline of an ocean, sea, lake, or river. It usually consists of loose particles, which are often composed of rock, such as sand, gravel, shingle, pebbles, or cobblestones. The particles comprising the beach are occa-
sionally biological in origin, such as mollusc shells or coralline algae. Wild beaches are beaches that do not have lifeguards or trappings of modernity nearby, such as resorts, camps, and hotels. They are sometimes called undeclared, undeveloped, or undiscovered beaches. Wild beaches can be val-
ued for their untouched beauty and preserved nature. They are most commonly found in less developed areas including, for example, parts of Puerto Rico, the Dominican Republic, Thailand, the Philippines and Indonesia, but they are also found in developed nations such as Australia and New Zealand.
Beaches typically occur in areas along the coast where wave or current action deposits and reworks sediments. Although the seashore is most commonly associated with the word beach, beaches are found by lakes and alongside large rivers. Beach may refer to: small systems where rock material
m a a g s T b a b T p p T ( o w
moves onshore, offshore, or alongshore by the forces of waves and currents; or geological units of considerable size. The former are described in detail below; the larger geological units are discussed elsewhere under bars. There are several conspicuous parts to a beach that relate to the processes that form and shape it. The part mostly above water (depending upon tide), and more or less actively influenced by the waves at some point in the tide, is
termed the beach berm. The berm is the deposit of material comprising the active shoreline. The berm has a crest (top) and a face — the latter being the slope leading down towards the water from the crest. At the very bottom of the face, there may be a trough, and further seaward one or more long shore bars: slightly raised, underwater embankments formed where the waves first start to break. The sand deposit may extend well inland from the berm crest, where there may be evidence of one or
more older crests (the storm beach) resulting from very large storm waves and beyond the influence of the normal waves. At some point the influence of the waves (even storm waves) on the material comprising the beach stops, and if the particles are small enough (sand size or smaller), winds shape the feature. Where wind is the force distributing the grains inland, the deposit behind the beach becomes a dune. These geomorphic features compose what is called the beach profile. The beach profile changes