A global network of sensors designed to detect hydroacoustic signals was installed to monitor compliance with the Nuclear Test-Ban Treaty of 1963. Scientists later found that earthquakes and volcanic activity occur almost exclusively at the edges of tectonic plates.set sail on an exploration of the mid-ocean ridge between South America and Africa.
( Appalachian orogenic belt and Caledonian orogenic belt.) According to this model, subduction in this ocean in Ordovician times (485.4 million to 443.8 million years ago) led to the foundering of the continental shelves and the formation of volcanic arcs.
The basaltic complexes of western Newfoundland were interpreted as ophiolitic complexes representing slivers of oceanic crust that escaped subduction as they were emplaced onto the continental margin.
Some of the other hallmarks of subduction—such as the high-pressure low-temperature metamorphic belts and the preservation of ophiolites—are very poorly represented in orogenic belts (belts of former or actual mountain ranges resulting from crustal deformation related to subduction or continental collision) that are older than 600 million years.
To some geoscientists, this implies that tectonic processes guiding the evolution of Earth were different from those of today.
Wilson was impressed with the similarity of thick sequences of Cambrian-Ordovician marine sediments to those of modern continental shelves.
In a Pangea reconstruction, Wilson showed that these shelflike sedimentary sequences extend along the entire length of the mountain chain from Scandinavia to the southeastern United States.
This ocean was subsequently named Iapetus, for the father of Atlantis in Greek mythology.
The concept that oceans may close and then reopen became known as the Wilson cycle, and with its acceptance came the application of plate-tectonic principles to ancient orogenic belts.
These underwater mountain ranges encircling the planet form as Earth's plates separate. Hess developed the idea that oceanic crust forms along mid-ocean ridges and spreads out laterally away from the ridges. They noted that this would appear over geologic time as bands of crust that exhibit alternating patterns of magnetic polarity.