Higher Sea Levels 6000 Years Ago or "When the Surf was really up!!"
by Tom Jackson, Pacific Legacy, Santa Cruz, CA
During the last glacial maximum, some 18,000 years ago, a person could stand at the site of modern Moss Landing, look westward along the deep chasm of the exposed Monterey Canyon and glimpse the ocean shore a mile away. As the climate warmed, polar ice sheets and glaciers melted rapidly; sea level rose. Perhaps 10,000 years later the California coastline came to look much as it does today.
There is evidence that Native Americans had settled in the area about 10,000 years ago. Sites along Elkhorn Slough have remains of Native American occupation dating 8,000 to 6,000 years ago, including abundant dietary refuse indicating harvesting of species in both sea and slough environments. But these sites were abandoned between roughly 6,000 and 4000 years ago. Some 2-3000 years later these sites were reoccupied. Since the 1980’s, archaeologists working at sites in the Moss Landing area have struggled to explain this period of vacancy.
To provide a possible answer to the question, we need to take a trip to Australia (well, not literally). On Australia’s geologically very stable coastline is clear evidence of a sea level change about 6,500 years ago that put sea level approximately 1.7 meters higher than today. Other studies from settings as diverse as the Niger River estuary of Africa to the coasts of India and Vietnam support this interpretation. The consequences of this sea level change for Native Americans living along the early Elkhorn estuary were disruptive to say the least.
The tidal shallows from which shellfish were collected, sharks and rays netted, and birds and sea mammals hunted were inundated under 1.7 meters (nearly six feet) of ocean water. As the ocean pushed inland, it inundated formerly dry tracts of land, disrupting plant and animal communities, dislocating Native Americans from settlements occupied for thousands of years, and transforming the landscape upon which they depended for sustenance.
The sea level which had risen, fell again in less than 2,000 years (a blink of an eye in geologic terms). Fast enough that the plant and animal communities along the shoreline were left unstable. The once abundant resources of the early Elkhorn estuary would not become reliably available again until about 3,000 years ago.
With the stabilization of a sea level that is familiar to us today, Native Americans resumed their previous adaptations to the estuarine environment, reoccupied sites abandoned thousands of years earlier and continued their cultural patterns until recent times.
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