Atlantic Ocean; The Oceans; Scientific American Presents; by Staff Editor; 2 Page(s)

The Atlantic Ocean is named for Atlas, who according to Homeric myth held heaven up with great pillars that rose from the sea somewhere beyond the western horizon. Though not the boundary between heaven and earth, the Atlantic does separate Africa and Europe in the east from the Americas in the west. The Mid-Atlantic Ridge, which runs down the middle of this basin, marks the location of tectonic spreading, where frequent volcanic eruptions continually build up oceanic crust. This concentration of active volcanism can be seen firsthand in Iceland, where the Mid-Atlantic Ridge rises entirely out of the sea.

The tectonic motion away from the Mid-Atlantic Ridge sometimes generates offsets, which scar the floor of the ocean in long east-west-trending fractures. As with the other ocean basins, the movement of tectonic plates over deeply seated foci of intense heat, called hot spots, leaves traces of ancient volcanic activity. Some of these volcanic remnants, such as the New England Seamount Chain, appear only as subtle pinpricks in this global view (right); others, such as the Walvis Ridge and the Rio Grande Rise, make up prominent welts.