【摘要】 <正> 我们于1973—1975年编制了1/200万我国东北大小兴安岭多年冻土分区图,目的是揭露和反映多年冻土形成、分布及发育的地带性和区域性规律,及其与自然因素的关系,同时为该区生产建设及远景规划合理布局提供依据。 此文是该图的文字说明和补充,在本文中该图已缩成1/600万,图中界线作了修改(图1)。更多还原

【Abstract】 Considering the close relationship between the actual distribution of permafrost in this district and the annual mean air temperature, we take the latter as the basis for the determination of first-class zones. Then the whole district may be divided into four zones, namely 1) the region north of -5.0℃ isotherm is a large area of perennial frost zone; 2) the regionbetween -5.0℃--3.0℃ isotherm is an insular thawing permafrost zone; 3)the region between -3.0℃ isotherm and the southern limit of the permafrost is an insular permafrost zone; 4) the region south of the southern limit of the permafrost is a seasonal freezing ground zone. According to different development conditions and features of permafrost, geomorphology and geological structure boundary, the insular thawing permafrost zone could be subdivided into two second-class regions, while the insular permafrost zone into five second-class regions.更多还原