Multivariate analysis of the location of rock glaciers and the environmental implications in a tropical volcano: La Malinche (Central Mexico)

摘要

La Malinche volcano is located in the eastern sector of the Trans-Mexican Volcanic Belt (TMVB). At least, five glacial advances have been documented in the Pleistocene for higher volcanoes of the TMVB. La Malinche and Nevado de Toluca volcanoes were severely affected by periglacial processes during the last two glacial advances. These processes produced landforms such as rock glaciers and scree slopes on La Malinche. This study has two primary purposes: to develop geomorphologic mapping of the La Malinche summit area on a scale of 1:25,000 and include glacial and periglacial landforms, and to analyze the topographic conditions where rock glaciers developed by using multivariate analysis. The geomorphologic map was obtained through photo-interpretation and fieldwork where volcanic, glacial, periglacial, fluvio-glacial and mass wasting landforms were observed. To carry out the analysis of the topographic parameters, a digital elevation model (DEM) was used. The Principal Component Analysis (PCA) was useful in identifying specific factors that explain correlations between topographic variables. Results of PCA show that altitude is the main factor in controlling the location of periglacial landforms. Cluster Analysis (CA) was helpful in classifying fossil rock glaciers according to height similarities, and two groups were obtained where two possible generations of rock glaciers were established. Results from multivariate analysis, indicated that geomorphic processes and landform development at the summit area are highly sensitive to climatic oscillation. Periglacial landforms on the summit area served as indicators of environmental change.