ENG-1988 — Page 364

21

m

The Environment

HONG KONG's natural environment is subject to enormous pressures from the very dense population (see Chapter 22) and the demands, frequently conflicting and always compet- ing, that the community makes upon it. Full and often excessive use of the environment is made for recreation, education, the support of primary industries, and the disposal of wastes.

This chapter describes the main aspects of the natural environment, the basic environ- mental protection framework and its further development in 1988. An account of the meteorological, geophysical and related services provided by the government is included together with an account of the significant meteorological events during 1988.

Topography and Geology

Hong Kong lies on the margins of the ancient Sinian landmass formed more than 600 million years ago and which now extends from Shandong in northern China to the Gulf of Hainan. The geological strata forming the landmass were originally deposited in submarine environments but were folded and faulted in subsequent mountain-building earth move- ments. A second period of mountain building, beginning about 150 million years ago, was accompanied by the intrusion of granite masses and explosive volcanic activity that resulted in the deposition of thick layers of ash and lava. The mountains formed of these deposits were subsequently eroded and the material was washed from the slopes and deposited in the valleys, plains and shallow seas. From the beginning of the Quaternary period, about two million years ago, the lower-lying areas of the region were exposed as sea levels fell due to the entrapment of water in the expanding polar ice caps. Warming of the climate and melting of the polar ice also resulted in a rise in sea level and the inundation of the low-lying areas. About 100 000 years ago, Hong Kong was surrounded by broad plains crossed by rivers depositing sands and gravel. These plains were gradually inundated by the sea in the final marine incursion that began about 15 000 years ago and ended when the sea reached more or less its present level about 6 000 years ago.

The erosion of the hills and deposition in the valleys increased rapidly following destruction of the natural vegetation during the widespread colonisation of the Hong Kong area during the Song Dynasty (960–1279). In more recent years, the extensive denudation that took place during the Second World War was reversed as the population became concentrated in the urban area. Hong Kong's granitic and volcanic rocks are generally deeply weathered and prone to landslides if disturbed, but can be excavated quite easily for use as reclamation material. Sand and gravel dredged from offshore areas now also provide material for this purpose.

Hong Kong has few mineral resources, although deposits of lead, zinc, quartz, beryl and graphite have been mined in small quantities while iron and tungsten were once extracted in