frostless zone

(meteorology) The warmest part of a slope above a valley floor, lying between the layer of cold air which forms over the valley floor on calm clear nights and the cold hill tops or plateaus; the air flowing down the slopes is warmed by mixing with the air above ground level, and to some extent also by adiabatic compression. Also known as green belt; verdant zone.

An area of undeveloped land encircling a town. An early green belt, about 15 km wide, was set up in the 1950s around Greater London in order to limit the spread of suburbs.

Other cities have followed this example by restricting development in the semi-rural areas beyond the built-up zone. The amount of new building is restricted although by no means completely banned. In some cases, development has been switched to areas beyond the green belt which is then sandwiched. Later motives for creating green belts have been the provision of open areas for recreation and the preservation of agricultural land. Some planners advocate the establishment of green ‘wedges’ which project into the city rather than a green belt.

Swathe of undeveloped land (e.g. agricultural land, forest, heath-land, wild country, etc.) around a town or city, protected to prevent it being built on. Loudon proposed such a benefit to London, partly to contain its sprawl, as early as the 1820s, and the idea was subsequently adopted by the promoters of garden cities and New Towns. The green belt around London preserved large areas of countryside in several counties where otherwise development would have been difficult to resist. See stein, clarence.

Bibliography

• Me. Miller(1992, 2002)

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