ENG-1954 — Page 303

HONG KONG ANNUAL REPORT, 1954

of the tropics, frosts even on Tai Mo Shan are of the rarest occurrence, and weathering depends almost com- pletely upon the chemical action of the atmosphere aided by the alternation of wet and dry seasons. Erosion is likewise due to water action which is at a maximum during the torrential rains of the summer monsoon. Again denudation is aided by the excessive wind velocities of the typhoons and to a much less extent by the gentler breezes of the dry winter monsoon from central China. Because of the destruction of forest growth and vegetation wrought by the agricul- tural population by sickle and grass fires, the soil and rock mantle are left unprotected except by their own cohesion. Intensive efforts have been made to limit and control these nuisances by rigid regulations and systematic reafforestation but bare rock surfaces and loose boulders still occur commonly on the higher surfaces and steeper slopes.

The laterite-type product of decay, is locally such, however, as to provide an impervious mantle for the underlying rock. In colour and composition the products of weathering accurately reflect their rock origin. Although frost action is absent, mechanical disintegration due to hydration, carbonation and temperature changes, has resulted in the formations of gravel and boulders over the surfaces of some rock types. The net result of the erosion cycle is that of an upland system with rocky mountain peaks and well defined ridges giving an impression of partly matured topography. In some areas the topography shows that adjustment to rock structure and resistance to weather- ing and erosion is very complete. This is evidenced particularly in the general anticlinal structure of the valleys. The Tolo Channel is a notable example.

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