Mystery Solved: How The West Was Formed

There's something off about the way scientists have been explaining the formation of the western quarter of North America.

For years researchers have generally accepted the theory that a massive oceanic plate called the Farallon plate acted like a conveyor belt, moving everything above it along until it retreated beneath the lighter American plate. Any crustal fragments swept east by this movement were believed to have smashed into the American plate, forming today's jigsaw called the North American Cordillera - a series of mountain ranges, including the Rockies, that stretch throughout the western edge of the continent.

The only problem was, there were inconsistencies with this theory - a major one being that the western coast of South America doesn't show any signs of similar activtity, which many believe ought to have been the case.

And while most scientists were happy to accept the incongruities and move on, Karin Sigloch, a geophysicist from Ludwig-Maximmilians University, and Canadian geologist Mitchell Mihalynuk decided to examine the situation further.

What they found, according to an article published in the journal Nature, revises 200 million years of geological history.

Instead of just two plates at work, Sigloch and Mihalynuk used seismic tomography to determine there are in fact four. They named the new plates - now located between 600 and 1100 miles deep under the planet's surface - Angayucham and Mezclara, and explain that the Rockies and other land formations in the same region of the world are in fact a conglomerate of pieces from each.

Corroborating their findings, Sigloch and Mihalynuk were able to identify several deep-sea trenches that they believe mark the subduction sites of these newfound plates, a process that would have yielded volcanos and, as a result, new material for the American plate to attach itself to.

Knowing this opens up a whole new realm of research for geologists, as Imperial College London's Saskia Goes showed on the journal's site News and Views, when she asked whether the westward of subduction, which pulled North America west, might have caused the opening of the Central Atlantic Ocean.