Morphometric evolution of cinder cones

Abstract

Basal diameters ( W co) for 910 cinder cones range from 0.25 to 2.5 km with a median of 0.8 km and a mean of 0.9 km. For 83 fresh cinder cones, cone heights ( H co equal 0.18 W co, and crater diameters ( W cr) equal 0.40 W co. These results - from cones in different parts of the world - confirm and extend Porter's (1972) conclusions based solely on Mauna Kea cones. Changes of W co, W er, and H co during the 9-year eruption of Paricutin generally followed Porter's rules, but two cones in Kamchatka (Tolbachik volcano) had nearly constant values of W cr throughout their growth, reflecting constant eruption conditions. Growth rates vary from cinder cone to cone and with time for a single cone. Cinder/spatter cones on Piton de la Fournaise and Etna grow slowly, whereas the Tolbachik cones and Vulcan grew to hundreds of meters in a few days. For sixteen cones, a statistically significant relation exists between average cone growth rate and ultimate cone volume. The result parallels Walker's (1973) finding that high eruption rates produce long lava flows. Additionally, this conclusion, coupled with Fedotov's (1976) theory of magma rise, implies that cinder cone volume is directly proportional to magma source depths. Crustal thickness may limit cone growth. Fifty percent of observed cinder cone eruptions last less than 30 days and 95% are over in one year or less. Almost invariably a cinder cone eruption produces a lava flow as well as a cone. There is a strong correlation between cone volume and flow volume. Cinder cones have smaller volumes than their associated flows, and commonly a lesser volume than associated mantle ash deposits.