A Submarine Slope of Southern California

Abstract

Sounding of a submarine basin slope near San Pedro, California, shows it to be steep (9°-18°) from the shelf break at 170 feet to a depth of between 1,400 and 1,800 feet. Many small gullies extend down this slope. The lower slope, to depths between 2,300 and 2,600 feet, is less steep, is not crossed by the gullies, and is believed to be an apron of landslide debris contributed from the upper slopes through the gullies. Mud on the slopes is thicker than 10-18 feet in spite of the steepness. It is suggested that the mud accumulates on the slope, and some of it periodically slides away, part being deposited at the base of the slope, and part forming turbidity currents that deposit gravels and clean sands on the floor of the adjoining basin to depths as great as 3,000 feet.