Computer-simulation models of scoria cone degradation in the Colima and Michoacan-Guanajuato volcanic fields, Mexico

Abstract

Scoria (cinder) cone degradation can be correlated with the length of time a cone has been exposed to erosive conditions, and the systematic decrease with increasing age of cone height, cone height/width ratio, and slope is the basis for relative dating of cones by comparing their morphometric parameters. Degradation of scoria cones in the Colima and Michoacan-Guanajuato volcanic fields, Mexico, offer an example of how the morphologic changes associated with increasing age can provide a basis for dating cones by a relative scheme or a relative scheme calibrated by radiometric dates. To further study the degradational evolution of scoria cones, a computer model for simulating their erosion has been formulated. This model can utilize either a linear or a nonlinear diffusion-equation algorithm expressed in finite-difference form to operate upon a three-dimensional scoria cone input as a matrix of elevation values. Aided by calibration with computer simulated degradation, cone erosion rates were calculated for the younger scoria cones in the Michoacan-Guanajuato volcanic field. These erosion rates were then extrapolated to determine the ages of the older cones in this volcanic field as well as in the nearby Colima volcanic field. The oldest cone age group in the Michoacan-Guanajuato field has an estimated mean age of approximately 100,000 years B.P., while the oldest cone age group in the Colima field has an estimated mean age of approximately 250,000 years B.P. The erosional history of these small-volume basaltic centers may reveal the effects of climate change. Erosional modifications of Volcan Telcampana, a scoria cone in the Colima volcanic field, were simulated by the three-dimensional computer model.