Bra allows the wearer to use the tighter hooks as the bra stretches during its lifetime. Bras may be designed to enhance a woman's breast size, or to create cleavage, or for other aesthetic, fashion or more practical considerations. Nursing bras are designed to aid breast-feeding. Compression bras, such as sports bras, push against and minimize breast movement, whereas encapsulation bras have cups for support. Breast support may be built into some swimsuits, camisoles and dresses. Bras come in a variety of styles, including backless, balconette, convertible, shelf, full cup, demi-cup, minimizing, padded, plunge, posture, push-up, racerback, sheer, strapless, T-shirt, underwire,
Continental shelf an advancing oceanic plate dives beneath continental crust in an offshore subduction zone such as off the coast of Chile or the west coast of Sumatra. The largest shelf – the Siberian Shelf in the Arctic Ocean – stretches to in width. The South China Sea lies over another extensive area of continental shelf, the Sunda Shelf, which joins Borneo, Sumatra, and Java to the Asian mainland. Other familiar bodies of water that overlie continental shelves are the North Sea and the Persian Gulf. The average width of continental shelves is about . The depth of the shelf also varies,