USING CINDER CONE MORPHOLOGY TO CONSTRAIN AGE (SAN FRANCISCO VOLCANIC FIELD REU)

The San Francisco Volcanic Field of northern Arizona is home to over 600 cinder cone volcanoes, few of which have precise age estimates. Photogrammetric 3-D modeling, numerical modeling, and analog modeling are used to show the effect of how varying sediment diffusivity constants (k values) and presence or lack of an agglutinated (welded spatter) rim impact the height and width of a cinder cone’s erosion profile over time. This change in profile height-to-width ratio is a useful metric for indicating relative cone age.

The effect an agglutinated rim has on cone morphology evolution is explored with a surface process model on idealized cones. Weathering processes are simulated through numerical modeling (two-dimensional nonlinear diffusion) using two different sediment transport rate (k values, one for the cone flank and one for the ring of agglutinate on top. Non-agglutinated cones show a greater decrease in height and increase in width over time, resulting in a lower height-to-width ratio and a higher rounding profile than agglutinated cones. The presence of an agglutinate top lessens the amount of rounding, producing a “neck” as the cone flank erodes. Thus, the agglutinated cones have “younger” height-to-width ratios. Sand cones constructed and eroded through analog modeling show profiles that are similar to the numerical model results, with the spray-adhesive-agglutinate cone having a prominent neck and a greater height-to-width ratio.

Cone erosion profiles are altered by presence or lack of agglutinate and rate of sediment transport, which is dependent on climate. Height and width measurements of a cone, the cone’s estimated age, and the k values corresponding to the climate of the cone’s region, can be used to make a calculation of relative age. This is especially beneficial for gathering of age data of cones in remote or hard to access locations, including locations on other planets.