HOW FAR CAN THE SCORIA GO?: TRANSPORT OF SCORIA FROM THE CINDER CONES TO SODA LAKE BASIN IN MOJAVE NATIONAL PRESERVE

In Mojave National Preserve, scoria originating from the field of cinder cones can be observed nearly 15 miles away from the cones as well-rounded to sub-angular shaped, pebble- to boulder-sized deposits on top of sandy flats near the low-elevation ephemeral Soda Lake. How was the scoria transported to these locations? Under what conditions? We investigate the mechanized transport of scoria in an arid environment by focusing on the following research goals: 1) interpret method of transport and 2) estimate magnitude of flow. Our methodology includes a combination of field observations and modeling. We hypothesized that the scoria was fluvially transported based on sedimentological evidence, including the lobe-shaped fans. We tested this hypothesis by modeling storm response and observing flow, sediment mobilization, and scouring using KINEROS2. Modeling indicated that heavy precipitation in this area, like a summer monsoon, mobilized a large amount of sediment with flow velocities orders of magnitude less than required to move cobbles. We then hypothesized that the sand mobilized and acted like a conveyer belt to move the cobble- to boulder-sized scoria sediment. We tested this in the field by trenching beneath scoria cobbles and boulders and making sedimentological observations. This theory was supported by observations of the subangular shape of the scoria, massive sand in the subsurface, and sand in the scoria vesicles. In summary, we interpreted that scoria clasts were transported nearly 15 miles in a sand slurry from monsoon-like, short duration, intense summer rain events.