THE deep-diving submarine Alvin has found the largest field of hot water vents yet discovered in the Atlantic Ocean, according to Columbia University. The site is on the Mid-Atlantic Ridge, about 200 miles west of the Azores.

The researchers found seven-vent area spread over 15 acres of sea floor. Because it is at a relatively shallow depth compared with that of other vent fields and is only a day's trip from Portuguese ports in the Azores, American, British, French and Portuguese scientists want to establish a joint sea floor laboratory at the site. "To fully understand how these hydrothermal fields operate, we need to monitor them over time," said Dr. Charles H. Langmuir, a geochemist at Columbia's Lamont-Doherty Earth Observatory who is the expedition's leader.

What happens under those vents helps determine the chemistry of the ocean. Over eons, he Dr. Langmuir said, "all ocean waters eventually are pumped through the volcanoes at mid-ocean ridges."

As a result, mineral deposits, often with abundant sulfur, are formed on the ridges, some of which eventually become exposed on land as sea floor and continents collide.

Evidence of the vent field was found last fall when sulfide-rich rocks and unusual organisms were dredged up by an expedition of French and American scientists exploring the Mid-Atlantic Ridge. Dr. Langmuir then returned and the field was sighted by the deep-diving Alvin, operated by the Woods Hole Oceanographic Institution. It is only the third vent field discovered and sampled in the Atlantic; many have been found throughout the Pacific.

Map of the Atlantic Ocean showing location of Vent field.