Plate tectonics, geology, etc, is one of my passions. Being a journalist, my only real chance to indulge in it though is when it comes up in a story, such as this one.
Needless to say, the story before you now is one that could very well send you off on several different tangents, but we’ll deal with that later.
A recent discovery suggests that the plate tectonics – the process from which our continental plates move, reshape, form our mountain ranges and oceans – is not necessarily a constant activity.
Over much of scientific history, scientists have believed that tectonic movement was continual, albeit very slow. But a new study from researchers at the Carnegie Institution is putting forth an entirely different idea. They believe that not only have plate tectonics stopped once before, but they may do so again.
One of the fundamental views within plate tectonic theory is that, on a geological timescale, ocean basins are short lived. As plates shift beneath them, they open and close, being consumed by a process called ‘subduction.’
Subduction is the process by which two tectonic plates meet, head on. One tectonic plate will slide underneath the other, subsequently sliding in to the Earth’s mantle. An oceanic plate however, will almost always slide underneath a continental plate. As a result, the water will have to find somewhere else to be.
“The collision of India and Africa with Eurasia between 30 and 50 million years ago closed an ocean basin known as Tethys,” says Paul Silver of the Carnegie Institution’s Department of Terrestrial Magnetism. “But no new subduction zones have initiated south of either India or Africa to compensate for the loss of subduction by this ocean closure.”
Of course, the water will not always be totally relocated, as there will not always be a swap. In the case of the Pacific Ocean – where most of our subduction zones are currently located – it is a hotspot for volcanic and earthquake activity; a corollary to subduction.
In their study, which is published in the January 4 issue of Science, Silver and former postdoctoral fellow Mark Behn (now at Woods Hole Oceanographic Institution) also present geological evidence, in the form of ancient igneous rocks, which indicate that approximately one billion years ago there was a cessation in the volcanic activity that is normally associated with subduction.
This idea fits suitably with other geologic evidence for the closure of a Pacific-type ocean basin at that time. This closure was also the catalyst that welded the continents in to one supercontinent, known as Rodinia. Geologists believe that it was this conglomeration of continents that halted subduction for awhile, only to be later reactivated when Rodinia split apart.
Harkening back to my original comments about indulging in plate tectonics, the mention of Rodinia and Tethys had me scurrying to look up (which I would suggest if you are interested, you should follow suit). It is fascinating to look at the history of our planet, a planet which has seen several supercontinents come and go. Mention by Silver that it was Africa and India that had closed the ocean basis Tethys fascinated me, especially as I looked at my world map to see where the two eventually came to rest.
If you’re not convinced, consider this small factoid; in 350 million years, it is expected that the Americas – both North and South – will eventually run in to Eurasia, eradicating the Pacific Ocean entirely. Now that, is something worth thinking about!
Joshua Hill, a Geek’s-Geek from Melbourne, Australia, Josh is an aspiring author with dreams of publishing his epic fantasy, currently in the works, sometime in the next 5 years. A techie, nerd, sci-fi nut and bookworm.
