Borgia, Andrea

Morphologic data for 147 cinder cones in southern Guatemala andwestern El Salvador are comparedwith data from the San Francisco volcanic field, Arizona (USA), Cima volcanic field, California (USA), Michoácan–Guanajuato volcanic field, Mexico, and the Lamongan volcanic field, East Java. The Guatemala cones have an average height of 110+/-50 m, an average basal diameter of 660+/-230 m and an average top diameter of 180+/-150 m. The generalmorphology of these cones can be described by their average cone angle of slope (24+/-7), average heightto- radius ratio (0.33+/-0.09) and their flatness (0.24+/-0.18). Although the mean values for the Guatemalan cones are similar to those for other volcanic fields (e.g., San Francisco volcanic field, Arizona; Cima volcanic field, California; Michoácan–Guanajuato volcanic field, Mexico; and Lamongan volcanic field, East Java), the range of morphologies encompasses almost all of those observed worldwide for cinder cones. Three new 40Ar/39Ar age dates are combined with 19 previously published dates for cones in Guatemala and El Salvador. There is no indication that the morphologies of these cones have changed over the last 500–1000 ka. Furthermore, a re-analysis of published data for other volcanic fields suggests that only in the Cima volcanic field (of those studied) is there clear evidence of degradation with age. Preliminary results of a numerical model of cinder cone growth are used to show that the range of morphologies observed in the Guatemalan cinder cones could all be primary, that is, due to processes occurring at the time of eruption.