ICE DANCING

Figure skating and ice dancing The rink used for ice-skating competitions has the art or sport of dancing on ice using skates. Although the English diarist Samuel Pepys claimed to have danced on the ice during London's great frost of 1683, modern ice dancing probably developed out of the Vienna Skating Club's adaptation of the waltz in the 1880s. The sport grew rapidly in popularity during and after the 1930s, and dance steps now recognized internationally include the 10- or 14-step, kilian, and varieties of the waltz, tango, and fox-trot. Dance steps are made up of figure-skating movements and are usually performed in set, unvarying patterns. Competitions include two compulsory dances, chosen annually by the International Skating Union (ISU); the original set pattern, an original dance created to a previously announced rhythm, with music and choreography chosen by the skaters; and the free dance, a long program performed to music and choreography of the skaters' choice, though the music must feature a dance rhythm. Ice dancers are judged on the difficulty and originality of the dance steps, their interpretation of the music, and their timing, unison, and speed. Final placement is determined by combining the scores from the four dances, with each of the compulsory dances making up 10 percent of the total score, the original dance 30 percent, and the free dance 50 percent. Unlike pair skating, ice dancing does not allow the introduction of movements of strength or skill (particularly overhead lifts and spins of more than one and one-half rotations), which are inconsistent with the character of the dance. In order to maintain the semblance of a dance rather than a pairs figure-skating routine, limits are placed on the time partners can be separated from each other; unless changing positions or performing a regulation jump or lift, partners must always be together in dance position. Also, for the original dance one of the skaters must be on the ice throughout the routine, and in the free dance both dancers must keep one skate on the ice at all times, except during lifts and jumps. World ice-dance championships, under supervision of the ISU, were initiated in 1952. Ice dancing has been an Olympic event since 1976. ice formation any mass of ice that occurs on the Earth's continents or surface waters. Such masses form wherever substantial amounts of liquid water freeze and remain in the solid state for some period of time. Familiar examples include glaciers, icebergs, pack ice, and ground ice associated with permafrosti.e., perennially frozen soil found in frigid regions. Approximately three-quarters of the Earth's fresh water is stored in the enormous ice sheets that cover Antarctica and Greenland and in the smaller ice caps, mountain glaciers, and pediments scattered throughout the rest of the world. These expanses of perennial ice originate on land by the compaction and recrystallization of snow and other forms of precipitation under the weight of successive layers that have accumulated year after year. They occur in every region, including the Equator at high altitudes. River and lake ice also occur over a good portion of the world. These sheets of ice remain on their respective surface-water bodies for varying lengths of time. Lakes in Antarctica, for example, are completely covered with ice throughout the entire year, whereas those in the colder areas of the continental United States experience freezing surface-water temperatures for only about 100 days in an average year. In the oceanic waters of the polar regions, ice occurs in the form of pack ice and icebergs. Pack ice consists of frozen saltwater that has been broken up and jammed together by wind. In most cases, it is only one to two years old, and it expands during winter to cover large areas of the oceans. During spring and summer, warmer temperatures cause the pack ice to melt, resulting in a retreat of its borders. The same warmer weather conditions promote the calving (breaking off) of icebergs at the seaward edges of glacial masses. These large chunks of ice (some extend several kilometres in length) then drift with the current toward the Equator. Permafrost usually consists of rocks and soil particles consolidated by ice. Such frozen ground occurs in regions where temperatures below 0 C (32 F) persist for two years or more (e.g., the Arctic and sub-Arctic). It is estimated that permafrost underlies nearly 25 percent of the terrestrial land surface. Various forms of ground ice are found in permafrost. The most conspicuous of these is foliated ice, which frequently develops in thermal contraction cracks in permafrost as wedge-shaped, vertical, or inclined sheets 2.5 cm to 3 m (about 1 inch to 10 feet) wide and 0.3 to 9.2 m deep. Another prominent form is pingo ice, which occurs horizontally or in lens-shaped masses.