ENG-1969 — Page 299

GEOGRAPHY AND CLIMATE

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formation are uncertain. The oldest sedimentary formation about which there is no doubt is the Tolo Channel Formation exposed on the north shore of Tolo Channel where it contains fossil am-

monites of Lower Liassic age.

Mineralisation associated with the intrusion of the granitic rocks has been economically beneficial to the Colony. Ores of lead, zinc and tungsten have been mined, while molybdenum, beryllium, tin and copper have been found in small quantities. Iron ore, formed by the pyrometasomatic alteration of limestone during the emplace- ment of one of the granitic intrusions, is profitably mined. Other minerals associated with the granites are feldspar and kaolin. Graphite, which formed by thermal metamorphism of coal, has also been mined.

Only the soil of the flat agricultural alluvial districts around Yuen Long in the Deep Bay area has any depth. Elsewhere in the Colony the soil cover is usually thin, sometimes no more than two or three inches. In general the natural residual soils are acid and of low fertility, needing the addition of lime, potash and superphosphates. The predominating crystalline character of the rock formations makes them unsuitable as aquifers for under- ground storage and this makes it necessary to concentrate on the collection of surface water for water supplies. The highly variable and erratic rainfall regime of the area alone accounts for many of the water shortages.

Hong Kong lies in the frost-free double-cropping rice zone of East Asia, although more profitable crops have increasingly dis- placed this form of land utilisation. Market garden cropping, including the cultivation of cut-flowers for the urban and suburban markets, is becoming increasingly important. Vegetables are grown throughout the year, but most particularly during the cooler months which form the main vegetable season. The upland areas, which are predominantly grass covered and in several places severely eroded, tend to have highly leached acid soils. Land utilisation of these areas is principally through afforestation, vigorously pursued since 1945.

CLIMATE

Although Hong Kong lies within the tropics it enjoys a variety of weather from season to season unusual for tropical countries.