中安第斯山地冰缘地貌特征

PERIGLACIO-GEOMORPHIC FEATURES OF THE CENTRAL ANDES MOUNTAINS

本区西侧相对湿热、冰缘带狭小、冰缘类型较少,而东侧正相反.22°—25°S的普纳高原地区以冰丘、冻丘为主,33°—35°S的多年冻土区有泥流舌、石冰川、分选环网等多种类型.本区石冰川主要为冷生型和冰川起因型,后者有一底部含水层.本区东西两侧冰缘地貌分布的差异主要是由不同气候造成的.

The west side of the Central Andes Mountains is relatively warm and humid, its pariglacial zone is narrow and periglacial type is few;the east side vice versa. Pingos,pal-sas are main features of the Puna Plateau between 22°-25°S;gelifluction lobes,rock glacier, sorted circle and nets as well as numerous periglacial types exist in the per-mafrost region between 33°-35°S. Rock glaciers here can be divided into two types: cryogenic and glacigenic types, the latter has a glacier ice core and a subpermafrost aquifer. The periglacial distribution difference which exists between the east and west sides is caused by different climates.The distribution of rock glacier terminal and permafrost lower boundary are regu-larly of 'latitudinal gradient 'in the world, that is, from 25°S southward on the southern hemisphere,the rock glacial terminal and the permafrost lower boundary descend 1000m or so with latitude increasing 10°,but the elevation only decrease 200~400m from 25°S northward. In the northern hemisphere, from 45°N northward to the elevation descends only 500m or so ,but from-45°N southward it decreses 1500m and more.