ENG-1999 — Page 482

THE ENVIRONMENT

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educational and recreational facilities and promoting better understanding of the countryside. Over 10 million visitors were recorded each year.

There are three marine parks and one marine reserve covering a total area of 2 160 hectares. They comprise scenic coastal areas, seascapes and important biological habitats. Similar to country parks, marine parks are managed for the purposes of conservation, education, recreation and scientific studies. It is intended to protect and conserve the rich and diverse communities of local marine life and habitats for the enjoyment of present and future generations. Marine parks and reserves are patrolled on a daily basis. Fishing is controlled with a permit system and is confined to local villagers and bona fide fishermen. Suitable facilities have been installed to facilitate compatible use of marine parks. Publicity and educational activities were organised for students and citizens during the year.

More areas are now being studied to assess their feasibility for designation as country or marine parks.

Topography and Geology

Hong Kong's natural terrain is dominated by mountains and hills with steep slopes, many of which descend directly into the sea. The seabed is relatively flat. The highest point in Hong Kong is Tai Mo Shan in the New Territories at 957 metres above Principal Datum. The deepest point is 66 metres below Principal Datum in Lo Chau Mun (Beaufort Channel) north of Po Toi Island.

The mountains consist primarily of volcanic rocks, with some of the lower hills formed of granite. Low-lying areas tend to be formed of granite or sedimentary rocks. In places, hill-slope debris forms a mantle over the bedrock and alluvium fills some of the valleys. Much of the seabed is covered by marine mud with some scattered sand banks.

Hong Kong lies on the southern edge of an ancient land mass. The oldest exposed rocks are Devonian fluvial sediments that were deposited 400 million years ago. The region was subsequently inundated by a shallow sea. Sediments from this period are represented by the Carboniferous marble of Yuen Long and Ma On Shan. The sandy and muddy sediments of the Permian rocks of Tolo Harbour are of alternate marine and continental deposits.

From the Jurassic to Cretaceous periods, between 170 and 140 million years ago, Hong Kong was the scene of violent volcanic activity. Thick accumulations of lava and ash were deposited. The eruptions were associated with the development of several giant craters (calderas). At deeper levels, the volcanic deposits were intruded by molten magma, which slowly crystallised to form granite.

Igneous activity had ceased by the beginning of the Tertiary period, 60 million years ago. Rocks now seen on the island of Ping Chau represent sediments laid down in a lake on the edge of a desert.

During the Quaternary period, spanning the last two million years, major glaciations in polar regions affected global sea level, which fell to 120 metres below the present level, leaving the site of present-day Hong Kong as much as 130 kilometres from the coast. At that time the flat areas between what are now the islands of Hong Kong were part of an extended Pearl River flood plain. In