306 The Environment
Management responsibilities include the protection of woodland and vegetation against fire, control of development, tree planting, litter collection, the provision of educational and recreational facilities, and the promotion of a better understanding of the countryside.
There are four marine parks and one marine reserve covering 2 430 hectares of scenic coastal areas, seascapes and important biological habitats. Marine reserves are dedicated to conservation, education and scientific studies. Fishing in marine parks is controlled through a permit system while it is totally banned in marine reserves. Publicity and educational activities are organised for students and members of the public.
Besides designating protected areas, the Government has been identifying and conserving sites of special scientific interest (SSSI), such as areas with special geological features and natural habitats of rare plants or animals, by exercising strict. land use planning and development controls. There are 67 sites listed in the SSSI register.
Topography and Geology
Hong Kong's natural terrain is characterised by rugged uplands flanked by steep slopes. The highest point is Tai Mo Shan (957 metres above Principal Datum) in the central New Territories, and the lowest point (66 metres below Principal Datum) is in Lo Chau Mun (the Beaufort Channel) to the north of Po Toi Island. The mountains are predominantly formed of volcanic rocks, whereas the lower hills consist mainly of granite. Low-lying areas are generally underlain by granite or sedimentary rocks. A layer of soft, weathered rock covers the bedrock in most places, slope debris. mantles the natural hillsides, and alluvium fills many of the valleys. Offshore, the seabed is covered with marine mud, with sand sheets occurring near the coast and in channels.
The oldest exposed rocks in Hong Kong are composed of river sediments that were deposited approximately 400 million years ago. From 350 to 290 million years ago, the region was inundated by a shallow sea, where limestones (now marble) and siltstones, found in western and central New Territories were deposited. From 170 to 140 million years ago, violent volcanic eruptions occurred with deposition of thick ash and lava layers and the development of several calderas (giant craters). At deeper levels, molten magma was intruded and slowly crystallised to form granite. Layered rocks now seen on the island of Ping Chau are younger sediments, laid down in a lake on the edge of a desert, about 55 million years ago.
During the last 2.6 million years, major glaciations caused successive lowering of sea level by up to 120 metres. This resulted in the coastline receding by about 100 kilometres south of Hong Kong. During interglacial periods, including the present time, the sea level rose and marine sediments were deposited.
A series of fifteen 1:20 000-scale geological maps and six accompanying geological memoirs have been produced by the Hong Kong Geological Survey. Two summary memoirs and a set of 1:100 000-scale geological and thematic maps that