oastlines don't come ready-made with beaches.

When ice ages cause sea level to drop, the sediment exposed on the continental shelf is eroded by wind and rain. As sea level rises with deglaciation, waves disperse the shelf's unconsolidated sediment and cut the bedrock itself. High seastands, such as we have at present, are generally the time when sand beaches build.

Today's sand beaches along the coast of southern California are the latest chapter in a history that originated thousands of years ago.

Reconstructing the story of this process tells us much about the littoral cells' response to different climate conditions.

Prevailing waves and sediment flux, erosion and deposition -- all were driven by past climates. Understanding coastal responses to climate patterns and sea level rise is a key component in modeling the future of California's coast under climate change scenarios.