marine terrace

A marine terrace is a coastal landform, usually a broad, horizontal platform made up of sediments and broken, water-ground and water-polished material cut from sea-cliff faces by breaking waves. South of Monterey, California, the terrace and wave-carved cliffs of the Carmelo formation show the history of life at the edge of Earth, relics of sea creatures embedded in sandstone, fossilized worm burrows, and the preserved remnants of collapsed canyon walls and ancient underwater landslides. These cliff faces reveal where lava once flowed, which is even now being broken and rounded into the sheets of dark pebbles and cobbles that mark parts of the terrace. At the edge of the Pacific plate farther south, at Torrey Pines State Beach, the forces of water carved a lagoon, which filled with mud when the sea rose. Terrace features of the Delmar formation there include flat expanses of exposed rock and, underneath the layers of mudstone and sandstone, a bed of fossilized oyster shells. Middens left by earlier people sometimes turn up in the cliffs, layers of ancient trees come to light. The ocean’s force breaks all of it down and works it, wave after wave, into the terrace slope. A drop in sea level or continental uplift can leave marine terraces isolated as marine benches. In areas such as Big Sur and Bodega Bay, California, a series of old marine terraces with steep front slopes and gently inclined tops descends to the sea. Linda Hogan

Linda Hogan