Glacial and periglacial geomorphology and its paleoclimatological significance in three North Ethiopian Mountains, including a detailed geomorphological map

摘要

Geomorphological investigations and detailed mapping of past and present (peri)glacial landforms are required in order to understand the impact of climatic anomalies. The Ethiopian Highlands show a great variety in past and contemporary climate, and therefore, in the occurrence of glacial and periglacial landforms. However, only a few mountain areas have been studied, and detailed geomorphological understanding is lacking. In order to allow a fine reconstruction of the impact of the past glacial cycle on the geomorphology, vegetation complexes, and temperature anomalies, a detailed geomorphological map of three mountain areas (Mt. Ferrah Amba, 12 degrees 51'N 39 degrees 29'E; Mt. Lib Amba, 12 degrees 04'N 39 degrees 22'; and Mt. Abuna Yosef, 12 degrees 08'N 39 degrees 11'E) was produced. In all three study areas, inactive solifluction lobes, presumably from the Last Glacial Maximum (LGM), were found. In the highest study area of Abuna Yosef, three sites were discovered bearing morainic material from small late Pleistocene glaciers. These marginal glaciers occurred below the modeled snowline and existed because of local topo-climatic conditions. Evidence of such Pleistocene avalanche-fed glaciers in Ethiopia (and Africa) has not been produced earlier. Current frost action is limited to frost cracks and small-scale patterned ground phenomena. The depression of the attitudinal belts of periglacial and glacial processes during the last cold period was assessed through periglacial and glacial land-form mapping and comparisons with data from other mountain areas taking latitude into account. The depression of glacial and perigladal belts of approximately 600 m implies a temperature drop around 6 degrees C in the last cold period. This cooling is in line with temperature depressions elsewhere in East Africa during the LGM. This study serves as a case study for all the intermediate mountains (3500-4200 m) of the North Ethiopian highlands. (C) 2015 Elsevier B.V. All rights reserved.