Processes during scoria-cone collapse as recorded by displacement of crater-rim blocks, Strawberry Crater, AZ
Courtney M. Pulido and Nancy R. Riggs
Strawberry Crater is one of several hundred scoria cones in the San Francisco volcanic field of northern Arizona. The process of scoria-cone formation and deconstruction are not completely understood despite the fact that they are the most common landform on Earth. Strawberry Crater is an unusual cone in that variable magma characteristics caused scoria during late stages of the eruption to become agglutinated upon deposition. This agglutinated scoria broke into large blocks that were displaced as late-stage eruption of lava breached the walls of the cone. Facies analysis shows that many of the blocks represent formerly continuous depositional horizons, which reflect a variance in magma-gas content and magmarise rate that may have affected the temperature and accumulation rate of pyroclasts, and therefore the degree of agglutination. Faults between blocks are dominantly vertical to subvertical regardless of block size. This suggests that breaching of the cone occurred abruptly as magma pressure exceeded the strength of the cone walls and released the remaining magma trapped in the cone, or that breaching was caused by an increase in magma flux as late-stage lava emanated from the bottom of the cone.
- Pulido, Courtney M.; Riggs, Nancy R., 2013, Processes during scoria-cone collapse as recorded by displacement of crater-rim blocks, Strawberry Crater, AZ, in: Geology of Route 66 region: Flagstaff to Grants, Zeigler, Kate; Timmons, J. Michael; Timmons, Stacy; Semken, Steve, New Mexico Geological Society, Guidebook, 64th Field Conference, pp. 153-158.