Elevation of Midocean Ridges and the Basement Age of JOIDES Deep Sea Drilling Sites
The East Pacific Rise in the North Pacific drops from a crestal elevation of 2,800m to a depth of 5600 m for 75m.y. old.crusf. All other active midocean ridges except the North Atlantic close to Iceland show the same increase in depth with age but, within a 400-m .spread, have generally shallower crestal elevations. Depths and basement ages from JOIDES Deep Sea Drilling Project site cores in the Pacific are in excellent agreement with the empirical depth versus age curve lor the North Pacific determined Irom magnetic and topographic profiles. Sites in the northwestern , Pacific are used to extend this empirical curve from a depth of 5,600 m at 75 m.y. B.P. to 5,900.m at 135 m.y. B.P. JOlDES data from the North Atlantic lall nose to jthis extended curve but consistently show 200- to 30d-m shallower crestal elevations in the oldest regions—evidence that certaini goographic areas show small ( ±300 m). but significant departures from the uniform depth versus age relation for the North Pacific. The cause of these departures is at present, unknown.
Figures & Tables
Edited by Peter A. Roma and published in 1976, Mid-Atlantic Ridge contains a collection of related articles reprinted from other Geological Society of America publications as well as a brief review of exploration of the Mid-Atlantic Ridge from 1960 to 1975.