Post-eruptive lahars related to the 1913 eruption in La Lumbre Ravine, Volcán de Colima, Mexico: The influence of ravine morphometry on flow dynamics.

A detailed historic record on Volcán de Colima, Mexico, of lahar activity and related phenomena dating back to the sixteenth century has proven that debris flows have caused more human casualties in the area than any other volcanic activity including pyroclastic flows. In this paper we present a multi-approach study of a relevant lahar (a non-cohesive debris flow with the largest runout and one of the most voluminous of the volcano) at Volcán de Colima, Mexico. Observations and information relevant to the lahar deposit and event including componentry, textural, sedimentological, stratigraphic, morphometric and geochronologic analyses and oral testimonies from eyewitnesses enable us not only to confirm a relationship between the studied outcrops and the 1913 Plinian eruption of the Colima Volcano (the most intense and large in volume eruption of this volcano of the last century), but also to find a clear and direct correlation among morphometric features such as slope, ravine width, curves and kinematics, flow patterns, flow transport mechanisms, volume, shape of clasts, granulometry and sub-unit formations. In particular, we maintain the slope has a marked control on the thickness of the deposits, deposited volume, longitudinal changes, and patterns of downstream changes in particle morphology and granulometry. All this information will be useful for generating or updating hazard maps, taking these lahars as a worst-case scenario. • The January 1913 Plinian eruption of the Colima Volcano was correlated with post-eruptive volcaniclastics. • The study confirms that these lahars are among the largest events that have occurred at the Colima Volcanic Complex. • The application of quantitative texture analysis in this study proves its sensitivity and accuracy. • Our paper demonstrates the strong probable relationship between deposit texture and changes in ravine morphometry. • Our study shows an exponential relationship between lahar volumes and runouts in the Colima Volcano area. [ABSTRACT FROM AUTHOR]