Kavli Institute
Coastal Morphology Group • Scripps Institution of Oceanography

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Sea Level

uring the past million years, the earth's climate has fluctuated between glacial and interglacial conditions and caused large oscillations in sea level.

The oxygen isotope curve reveals these ice age cycles and serves as a proxy for sea level changes. During full glacial conditions, sea level drops by 120 meters (~400 ft.) or more. During warm interglacials like the present climate, sea level is high because glaciers and ice caps melt.

Stillstands are times of stable sea level when the ocean is neither rising nor falling rapidly. During stillstands, waves erode the coast and cut platforms in the rocky shelf. The platform provides a gently sloping base for the formation of sand beaches.

What sea level means for the beach

Sea level curve for the last 18,000 years.
Click here to learn more about this sea level curve.

Sand beaches require a wide, gently sloping platform where sand is deposited and a beach can form. The present platform and sea cliff along the California coast were cut by wave action during the sea level stillstand of the last 6,000 years.

Sand beaches began to build in the Oceanside littoral cell about 5,000 years ago. Increased El Niño activity over the last 5,000 years brought enough sand to the coast to form beaches along the entire 84 km (~52 miles) of the cell.

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Coastal Morphology Group • Scripps Institution of Oceanography

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