Along the eastern margin of the Pacific basin is the East Pacific Rise, which is a part of the worldwide mid-oceanic ridge. Because a relatively small land area drains into the Pacific, and because of the ocean's immense size, most sediments are authigenic or pelagic in origin. Authigenic sediments include montmorillonite and phillipsite. Pelagic sediments derived from seawater include pelagic red clays and the skeletal remains of sea life. Terrigenous sediments are confined to narrow marginal bands close to land.
Salinity also varies latitudinally.
Water near the equator is less salty than that found in the mid-latitudes because of abundant equatorial precipitation throughout the year. Poleward of the temperate latitudes salinity is also low, because little evaporation of seawater takes place in these areas. The surface circulation of Pacific waters is generally clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. The North Equatorial Current, driven westward along latitude 15 deg north by the trade winds, turns north near the Philippines to become the warm Kuroshio, or Japan, Current. The Aleutian Current branches as it approaches North America and forms the base of a counterclockwise circulation in the Bering Sea.