Huge Area of Sea Floor Movement Off Iberian Coast

Continental Europe has started to move towards the United States as a new subduction zone forms off the Portuguese coast. This is the start of a cycle that will see the Atlantic Ocean reduce in size and finally close as what scientists refer to as a ‘passive margin’ becomes active.

A subduction zone is an area where one of the plates that cover the Earths’ surface is driven underneath the plate it is colliding into. Such faults are known to produce mega-thrust earthquakes when they get stuck and then slip allowing massive pressure to be released. The Indonesian quake of 2004 was caused by the subduction of the Indian Plate under the Burmese Plate and the Japanese quake of 2011 was caused by the subduction of the Pacific Plate under the Okhotsk Plate.

The Cascadia fault line off the coast of California is also a subduction zone. In this case it’s a long sloping fault where the Juan de Fuca Plate is being forced under the North American Plate.

The new fracture marks the start of activity at the South West Iberia Plate margin and is thought to be the start of a new Wilson Cycle. The Wilson cycle is named after J. Tuzo Wilson who recognized how plate tectonics fitted in with the geological record. It describes the coming together, and then the drifting apart that happens as the plates slide around on the Earths surface.

The consequences of this new movement is likely to be an increase in seismic activity. The large earthquake of 1755 that devastated Lisbon is an indication that convergent techtonic movement has been taking place for some time but for the first time scientists are able to prove it.

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