dome

In architecture, a roof form which is usually hemispherical and constructed over a circular, square, or octagonal space in a building. A feature of Islamic and Roman architecture, the dome was revived during the Renaissance period.

The dome first appears in Assyrian architecture, later becoming a feature of Islamic mosques (after the notable example in the Byzantine church of Hagia Sophia, Istanbul 532–37) and Roman ceremonial buildings: the Pantheon in Rome (about AD 112) is 43.5 m/143 ft in diameter.

Rediscovered during the Renaissance, the dome features prominently in Brunelleschi's Florence Cathedral (1420–34), Bramante's Tempietto at San Pietro in Montorio, Rome (1502–10), and St Peter's, Rome (1588–90). Other notable examples are St Paul's, London (1675–1710), by Christopher Wren, and the Panthéon, Paris (1757–90), by Jacques Soufflot (1709–1780).

In the 20th century Buckminster Fuller developed the geodesic dome (a type of space-frame).

Domes may be constructed of stone, brick, concrete, reinforced concrete, hollow tiles, timber, steel, or aluminium framing; and may be covered externally with lead, copper, and so on. For ideal visual effect, a hemispherical dome is satisfactory internally, but needs to be steeper than a hemisphere externally, or it appears insignificant. Hence, certain domes, such as St Peter's in Rome are of double construction, and some, such as St Paul's in London, are of triple construction, where the heavy stone lantern is carried by a brick cone entirely concealed between the outer and inner domes, the former being of timber framing covered with lead, and the latter of brickwork.

dome

A geologic feature that is the reverse of a basin. It consists of anticlinally folded rocks that dip in all directions from a central high point, resembling an inverted but usually irregular cup.

Such structural domes are the result of pressure acting upward from below to produce an uplifted portion of the crust. Domes are often formed by the upwelling of plastic materials such as salt or magma. The salt domes along the North American Gulf Coast were produced by upwelling ancient sea salt deposits, while the Black Hills of South Dakota are the result of structural domes pushed up by intruding igneous masses.