Nancy Leach, age 10, of Montgomery, Ala

In 1957, scientists of many nations got together to pool their brains and their efforts to give our old earth a thorough physical examination  Their work was called the International Geophysical Year and many aspects, of this famous IGY are still going on  Separate studies were made here and there and then followed the tremendous job of putting the pieces together  Instruments were used, many of them specially invented, to probe below the face of the sea  This IGY Warmation has given us a startling new map of the ocean floor 

The depth of the oceans of course# is measured from sea level, the average surface level of the world‑wide ocean waters  The depth of the Atlantic varies from a few inches near its tidal shorelines to trenches that plunge more than five miles below the surface  The shorelines of the continents slope in gentle ledges to a point where the ocean floor drops sharply a mile or two down to the deep ocean basin  The gentle ledges are the continental shelves, a watery worlds blue‑green with filtered sunlight and teeming with life  The ocean basin is blacker than blackest midnight 

The landscape of the ocean floor is more rugged than any of the dry land masses  There are ridges of massive mountain ranges foothills, lonely seamounts and flat‑topped mesas called guyots standing on the bottom of the ocean basin  There are flat plains, slopes and rises, canyons, deep trenches and fans of muddy debris piled up from the mouths of great rivers  There are steep cliffs, earthquake faults and seething volcanoes that shad an eerie light and clouds of bubbling gases in the midnight abyss  Some of the undersea peaks poke above the surface and form islands 

The main feature of the Atlantic floor is a vast range of mountains that sweeps down the center of the basin  the swerving S‑shape of the Atlantic as it swings down from the Arctic Ocean to the tip of South Africa where it turns around

into the Indian Ocean  The vast range varies from 300 to 1,200 miles in width  Most of its peaks are a mile below the surface, Iceland and the Azores are islands formed on peaks which poke above the surface 

The center of this vast Mid‑Atlantic Ridge is a cleft with a yawning raft, in some places five miles wider and bordered with steep cliffs two miles high, The massive ridge is cracked with awesome fractures and earthquake faults, At the equator it plunges into the Romanche Trench almost 26,000 feet deep and off Cuba it dips to even greater depths in the Puerto Rico Trench 

On both sides of the Ridge, the slopes tip and dip down in chains of low foothills  The Ridge with its family of ups and downs occupies one third of the Atlantic floor  Its feet stand on abyssal plains at the bottom of the ocean basin more than two miles below the surface  These plains are scarred with clefts and dotted with lonely mountains and guyots  Nearer the continents, the deep plains begin a slow climb upward to steep cliffs which are the doorsteps of the continental shelves 

If the Atlantic floor were smooth as a plate, it would be an easy job to estimate its average depth  But all the ups and downs make the job almost impossible  Recent studies found more mountain areas so the average depth may be a little less than the former estimate, which was two and a half miles