Rock glaciers, Central Andes, Argentina, Version 1

Primary rock glaciers are fed by avalanche chutes. At the El Salto rock glacier, surveys have been undertaken in order to determine the creep rate. Between 1981 and 1986 temperatures at elevations between 3500 and 3600 m were measured in the active layer to a depth of 1 m with a multipoint temperature recorder (Grant). On the basis of these measurement Buk (1983) determined that the permafrost table was at a depth of about 3 m and the base of the permafrost at 68 m. Similar conclusions were reached by Barsch and King (1989). As an illustration of the importance of avalanches to these forms, the base camp there was destroyed by an avalanche in November 1983. The surface of the basin of Morenas Coloradas is 54 square km, of which 10.4 square km is seasonally frozen ground. The remaining 60% of the surface is typically periglacial with rock glaciers as the most important forms. In the glacigenic rock glacier, the clean glacier ice ends in detritus-covered or morainic tongues which result in glacigenic ice being incorporated within the substrate. In this way, ice persists at lower altitudes and under very arid conditions (Lliboutry, 1986; Garleff and Stingl, 1986; Schrott, 1992). Interconnected rock glaciers are generated which undergo different phases of activity not always in agreement with those expected as a resulted of their elevations. That is, they continue to show signs of activity not only at the height of the present 0 degrees C air isotherm, but at lower elevations. In the last step downwards towards the valleys these rock glaciers become inactive, and finally morphologically relict or fossil rock glaciers are found. Meteorological, hydrological and geophysical measurements as well as 5 drillings to a depth of 5 m have been carried out in Morenas Coloradas. At an elevation of 3560 m the temperature oscillates around 0 degrees C (with a maximum variation of 0.5 degrees C) at depths between 4 and 5 m. The annual precipitation (1991-93) is 630 mm and the mean annual temperature is 1.6 degrees C. Using a calculated lapse rate of 0.52 degrees C per 100 m, the 0 degrees C isotherm occurs at approximately 3860 m, which represents a considerable rise in comparison with earlier years. It is assumed that this value is strongly influenced by climate warming in the 1980s and 1990s. Temperatures measured at different depths in Morenas Coloradas at 3560 m are positively correlated with the discharge of Rio Vallecitos (correlation coefficients of 0.8-0.9; significance p=0.01). There is no correlation with snowfall data, however, because of the influence of the 'zonda', a very dry and warm wind (up to 100 km/h) which impedes the accumulation of snow. Between 1978 and 1979, the zonda was active for more than 1000 hours. Discharge from the basin is of good quality and averages 505 l/s with a range from 230 l/s (early spring) to >1000 l/s (summer). In comparison, Schrott (1994) calculated the discharge of a rock glacier in the arid region of San Juan, Argentina to be only 5-8 l/s. These data are presented on the CAPS Version 1.0 CD-ROM, June 1998.原生岩石冰川（rock glacier）由雪崩槽供给物质。针对埃尔萨尔托岩石冰川，研究人员开展了勘测以确定其蠕变速率。1981年至1986年间，研究人员使用多点温度记录仪（Grant），在海拔3500至3600米的活动层（active layer）内1米深度处开展了温度测量。基于这些测量数据，Buk（1983）确定多年冻土（permafrost）顶面埋深约3米，多年冻土下限埋深为68米。Barsch与King（1989）也得出了相似的结论。为说明雪崩对这类地貌的重要性，该营地于1983年11月被雪崩摧毁。 莫雷纳斯科洛拉达斯（Morenas Coloradas）流域的总面积为54平方千米，其中10.4平方千米为季节冻土区。剩余60%的区域属于典型冰缘（periglacial）环境，其中岩石冰川是最主要的地貌类型。在冰川成因的岩石冰川中，纯净的冰川冰最终以被岩屑覆盖的冰碛舌形式终止，这使得冰川成因冰被嵌入岩土基质之中。通过这一机制，冰川冰能够在低海拔以及极端干旱环境下得以留存（Lliboutry，1986；Garleff与Stingl，1986；Schrott，1992）。相互连通的岩石冰川会经历不同的活动阶段，这些阶段并不总是与其海拔高度所预期的活动规律相符。也就是说，它们不仅在当前0℃气温等温线的海拔高度仍表现出活动迹象，在更低海拔区域亦是如此。在向山谷延伸的最下游区段，这些岩石冰川会停止活动，最终形成形态上的残留型或化石型岩石冰川。研究人员在莫雷纳斯科洛拉达斯流域开展了气象、水文与地球物理勘测，同时完成了5次深度达5米的钻探作业。在海拔3560米处，4至5米深度的温度在0℃左右波动，最大变幅为0.5℃。该区域1991年至1993年的年降水量为630毫米，年平均气温为1.6℃。基于计算得到的0.52℃/100米的气温直减率，当前0℃等温线的海拔约为3860米，与早年相比出现了显著抬升。研究认为这一现象与20世纪80年代至90年代的气候变暖存在强关联。巴耶西托斯河（Rio Vallecitos）的径流量与莫雷纳斯科洛拉达斯流域海拔3560米处不同深度的温度呈显著正相关，相关系数为0.8至0.9，显著性水平p=0.01。但该区域的温度与降雪量并无相关性，这是受“松达风（zonda）”的影响——这是一种干热强风，最大风速可达100千米/小时，会阻碍积雪堆积。1978年至1979年间，松达风的累计活动时长超过1000小时。该流域的径流水质优良，平均径流量为505升/秒，径流量范围为230升/秒（早春时节）至超过1000升/秒（夏季）。相比之下，Schrott（1994）测算得到阿根廷圣胡安干旱区一处岩石冰川的径流量仅为5至8升/秒。相关数据收录于1998年6月发布的CAPS 1.0版光盘中。