Recent lahars at Volcan de Colima (Mexico): Drainage variation and spectral classification

Volcan de Colima is the most active volcano in Mexico, and represents a high risk for more than 500,000 people. In 1998 the volcano renewed its activity, with the extrusion of a lava dome and subsequent lava and block and ash flows. During the recent period of activity pyroclastic products did not directly affect villages around the volcano, however, several lahars did. We used LIDAR topographic coverage, ASTER and LANDSAT images for the recognition of morphological changes in the drainage system and lahar detection. For lahar delineation we applied principal components analysis and canonical classification (Tasseled Cap) in order to perform a supervised image classification using the maximum likelihood rule algorithm. LAHARZ (objective delineation of distal debris flow hazard zones) has been used and tested using two topographic datasets with different resolutions, which provided evidence of the importance of high-resolution topographic coverage in hazard assessment. Finally a hazard map for labars is presented, showing that several villages and ranchos can be affected. In contrast, due to morphological changes produced by products of the intense explosive activity, other populated areas such as La Yerbabuena, are outside of the high risk zone. They could be affected by lahars only in case of cataclysmic eruptions such as the 1913 Plinian event. (c) 2007 Elsevier B.V. All rights reserved

Exploring the factors that influence the perception of risk: The case of Volcan de Colima, Mexico

Volcan de Colima has increased its activity considerably since 1998 with four periods of effusion and since 2003, daily Vulcanian explosions. During 2005 the magnitude of the explosivity increased, producing many pyroclastic flows, two of which reached over 5 km from the volcano, making them the largest events since the last Plinian eruption in 1913. A significant risk is also presented by the lahar hazard, with various examples of damage to infrastructure during the last few years and 23 people killed in 1955. Nearly 5000 people live in small settlements within 15 km of the volcano. Since 1997 six studies have been carried out in the region in an attempt to define the relationship that exists between the population and its neighbour. Although the methodologies used were different, each study considered the results of the previous and attempted to contribute further data to define geographical variation in the perception of risk. The results of the studies highlight the minor role of increasing activity on risk perception, and distance from the volcano was shown to not directly influence risk perception. In most cases it is the combination of various socio-cultural, historical and political factors that defines the perception of volcanic risk within these villages. By studying the social representation of the risk, such complexity could be better understood. The 1997-2000 information campaign evidently improved risk perceptio