Plate tectonics, the geological process in which large plates of crustal material slowly move around the surface of the Earth, is widely considered to be continuous, with material being created where plates move apart and consumed where they converge. However, new research published in the journal Science suggests that sometimes it takes a break.

According to Paul Silver from Carnegie Institution for Science, Washington, and Mark Behn of Woods Hole Oceanographic Institution, Massachusetts, in around 350 million years, the Pacific Ocean basin will close up, as the westward-moving Americas collide with Eurasia. At present, most of the world’s subduction zones – regions of convergence where one plate forces another down into the mantle – are located in this basin. Should the basin disappear, the subduction zones would go with it, effectively bringing plate movement to a halt until new subduction zones are created.

In support of their theory, they point to geological evidence that suggests that a small ocean was gradually closed by plate movement in the past. ‘The collision of India and Africa with Eurasia between 30 and 50 million years ago closed an ocean basin known as Tethys,’ said Silver. ‘But no new subduction zones have initiated south of either India or Africa to compensate for the loss of subduction by this ocean closure.

‘This could represent an important addition to plate tectonic theory,’ Silver said. ‘If plate tectonics is intermittent, then it will be necessary to understand the processes that control both its cessation and initiation.’


March 2008