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Recent findings by the Deep Sea Drilling Project explaining how the Isthmus of Panama was formed were announced at the AGU Annual Meeting in April by Tjeerd H. van Andel and G. Ross Heath of Oregon State University's Department of Oceanography as one of the principal results of Leg 16 of the Deep Sea Drilling Project. The cruise began in Cristobal, Panama, on February 5 and ended in Honolulu, Hawaii, on March 30.

During the first part of drilling vessel Glomar Challenger's sixteenth cruise, the shipboard scientists tested a hypothesis developed recently at Oregon State University and Lamont-Doherty Geological Observatory of Columbia University. On the basis of geophysical observations, this hypothesis suggests that 10 to 15 million years ago an ocean ridge extended eastward from the present position of the Galapagos Islands. This ridge split lengthwise as a rift zone grew from the eastern end. The southern half remained at its position near the equator while the northern half broke in several pieces that began a slow drift northward in response to thermal currents deep in the earth.