Scripps Center for Marine Archaeology




MISSION: We aim to understand how changes in sea level impacted the marine environment off California, and how these coastal changes shaped late Pleistocene and early Holocene occupation of the coastal zone, including influence on early migration into North America.

BACKGROUND: During the last glacial maximum, global sea level fell to more than 100 m below current levels, exposing a wide swath of the continental shelf. During the earliest occupation of North America (> 13,000 ybp) the exposed portions of the continental shelf would have been attractive sites for human settlement, encouraging exploitation of marine resources and travel along the coastal corridor. During the time period between 16,000 and 7,000 ybp, sea levels rose rapidly, interrupted by at least two periods with static sea level. The most significant of these events is known as the Younger Dryas (YD) episode, which occurred between 13,000 and 11,500 years ago, while the second is the 8.2 Kilo-Year (8.2KY) cooling event, which lasted between 8,400 and 8,200 years ago. These events allowed the development of shoreline wave-cut terraces with stable beach profiles and the accumulation of sediment deposits within coastal bays. On the Southern California coast, the YD episode formed a terrace that is now located at about 58 m water depth and the 8.2KY event formed a terrace at about 24 m water depth.

The archaeological record reveals that humans were living on the Channel Islands (off the Southern California coast) by about 13,000 years ago, where they lived primarily by fishing and shellfish collection. These early island inhabitants reflect a fully developed maritime economy that is distinct from the roughly contemporaneous Clovis tradition represented throughout much of interior North America. The lack of evidence for late Pleistocene settlements on the mainland coast of Southern California suggests that the offshore zone is worthy of investigation for evidence of the earliest occupations. Evidence for early marine adaptation along the Southern California coast is reflected in the hundreds of submerged cobble mortars and other artifacts (see image below) that have been found at numerous locales including off Del Mar, Solana Beach, Torrey Pines, and Point Loma, and in the area around La Jolla Cove and La Jolla Shores, adjacent to Scripps Institution of Oceanography.


  • PI: John Hildebrand, Professor, Oceanography, Marine Physical Laboratory, Scripps, UC San Diego
  • CO-PI: Isabel Rivera-Collazo, Assistant Professor, Anthropology; and Geosciences, Scripps, UC San Diego

Seismic reflection profile showing recent sediment layer above a buried river channel located off the southern California coast.

Model for sediment deposition in a southern California offshore river channel. Regions with high probability for offshore archaeological site material are designed by colored zones, along the former lagoon, on the margins of the river channel, a the base of a marsh deposit, and within the river channel itself.

Eustatic (global) sea level during the past 20,000 years, after Inman (2002). The Younger Dryas (YD) and 8.2 ka cold event are periods of relatively stable sea level during the time of rapid deglaciation and steady sea level rise.

Stone bowls recovered offshore from La Jolla in the early days of scientific diving by Scripps Institution of Oceanography (Marshall and Moriarty, 1964).