ENG-2008 — Page 353

The Environment | 285

eruptions were associated with the development of several calderas (giant craters). At deeper levels, molten magma was intruded and slowly crystallised to form granite. Igneous activity ceased 60 million years ago. Layered rocks now seen on the island of Ping Chau are younger sediments, laid down in a lake on the edge of a desert.

During the last two million years, the Quaternary Period, several major glaciations affected the polar regions. These caused successive lowering of world sea level of up to 120 metres, which resulted in the coastline being about 120 kilometres to the south. During the interglacial periods, such as the present time, global sea level rose and marine sediments were deposited.

Information about the geology of Hong Kong is presented in a series of fifteen 1:20 000-scale geological maps and six accompanying geological memoirs that were produced by the Hong Kong Geological Survey, a part of the Geotechnical Engineering Office. The Hong Kong Geological Survey has also published two summary memoirs and a set of 1:100 000-scale geological and thematic maps that synthesise the geology of Hong Kong. The detailed geological information is also available at the web-site of the Civil Engineering and Development Department.

Energy

Gas

Town gas and liquefied petroleum gas (LPG) are the main types of fuel gas used in Hong Kong for domestic, commercial and industrial purposes. LPG is also used as a fuel by some taxis and light buses while natural gas is used for electricity generation and production of town gas.

Hong Kong has about 2.3 million gas customers in the domestic, commercial and industrial sectors, of which town gas and LPG respectively accounted for 83 and 17 per cent of the total fuel gas sold in these sectors.

Town gas is manufactured at plants in Tai Po and Ma Tau Kok, which have daily throughput capacities of 9.66 and 2.6 million cubic metres respectively. There is a piping network of some 3 300 kilometres supplying town gas to about 1.6 million

customers.

LPG is imported into Hong Kong by sea and stored at five terminals on Tsing Yi Island before being distributed to approximately 664 000 customers and 58 LPG filling stations.

Natural gas is imported from the Mainland via submarine pipelines to the Black Point, Castle Peak and Lamma Power Stations for electricity generation and to Tai Po plant for production of town gas.

On August 28, 2008, the Hong Kong SAR Government and the National Energy Administration signed the Memorandum of Understanding (MoU) on the enhanced supply of natural gas to Hong Kong, among other things, in the coming two decades. According to the MOU, the Central People's Government (CPG) supported China National Offshore Oil Corporation's renewal of its supply agreement with