Sea Stack Frequency & Sediment Supply Along the California Coast

The vast majority of the world’s coastlines are rocky, with California’s coastline being no exception. These coastline types, and more specifically the California coast, exhibit a number of diverse morphologies including wide sandy beaches, pocket coves, and plunging cliffs. Another, less studied coastal feature found in these environments are sea stacks, remnants of former headlands separated from the coast through erosional processes. Several mechanisms have been proposed to explain the formation of sea stacks, including subaerial erosion, differential rates of erosion by rock type, and hydraulic compression. Limber and Murray (2015) examined another potential mechanism associated with coastal evolution, modeling abrasion-driven preferential erosion. In their models they found that under low sediment availability conditions, headland flanks were eroded away faster than the seaward heads, eventually evolving into sea stacks. Looking for observational evidence of their proposed mechanism, they documented the frequency of sea stacks along two distinct stretches of the California coast, one with high sediment availability and one with low. They recorded a higher number of sea stacks in the low sediment availability sample than in the high sediment availability area, results consistent with model predictions. Seeking to further test these predictions, I expanded the search area from discrete coast lengths to entire littoral cells (designated compartments used for sediment budget analysis) over the length of the state.