Plate tectonics is now one of the universally accepted truths of the earth sciences. The originally controversial theory (in the 1950s!!) that the Earth’s crust is made of a series of ‘tectonic plates’, i.e. MASSIVE chunks of rock moving around on top of the mantle (the bit below the crust and above the core), is now fully believed. These plates interact with one another in a variety of ways; some slide past one another, some slip under others, and some crash together and build topography upwards, and some move apart and new crust forms in the gap. However, since I started learning about plate tectonics in school, I learned the names of all the different plates, but I never thought in my life I would see a NEW PLATE being created. I was wrong.
On the 11th April this year, 2 massive earthquakes ripped through the seafloor of the Indian Ocean. This has happened before of course, the Boxing Day 2004 tsunamigenic* earthquakes were located on a subduction zone (where one plate slides beneath another) along the eastern margin of the ocean. The weird thing about the April quakes is that they did not happen on the plate boundary, or anywhere near it. Furthermore, the seismic signal (a complex series of lines that mere mortals cannot comprehend) suggested that they were not subduction zone earthquakes a.k.a ‘thrust faults’, but were actually ‘strike-slip’ quakes where one chunk of rock slips past another laterally, but they do not collide into each other.
Now it becomes complicated. When we think about plate tectonics, we have to imagine first off that the Earth is a sphere…CRAZY, right? We then imagine splitting the surface of that sphere into a series of chunks, the tectonic plates. These plates then all start to move by rotation in various ways, which means that the ways in which plates collide change too. Now to complicate things more, the plates themselves are not completely rigid. In the case of the April quakes, the vast ‘Indo-Australian’ plate had been moving in a non-uniform way… such that even though they are on one plate, Australia had been moving faster than India, attempting to make a break for it towards SE Asia. This means that the plate is no longer happy together and as a result, it began to tear along what may be a strike slip fault, which may be a precursor for a new plate boundary. This is what the April quakes appeared to show, and the implications of this are huge. A new plate boundary means we have to redraw literally TENS of maps, and school children will be forced to learn the name of yet another plate. There are already too many plates, so I leave you with this message as expressed by the favourite jumper of my old tutor in the UK…
STOP PLATE TECTONICS
*tsunamigenic: needlessly long word…means ‘generates a tsunami’
P.S. once again, New Scientist describes this better than me here