Scientific debate often rings immediately boring in many minds, with assumptions suggesting that the topic at hand is simply an academic one, and nothing important or impacting. Such is not the case for the debate over whether plate tectonics apply on the continental scale as well as on the fault scale, as more knowledge in these areas will help to broaden our understanding as well as our preparedness of earthquakes, a topical issue.
Harvard geophysicists Brendan Meade and Jack Loveless have tackled the issue of whether plate tectonics are applicaable on a continental scale in a recent journal entry in Earth and Planetary Science Letters.
“There has been a great debate over plate tectonics since the 1960s,” said Meade, associate professor of earth and planetary sciences. “The interactions between continents are so complex. A lot of people in the field believe that continental interactions are too complex to be explained by plate tectonic theory.”
Meade and Loveless say that yes, plate tectonics apply on a continental scale, and they focused their study on the Tibetan Plateau where the continent of India is pressing north into the rest of Asia, deforming and interacting in ways that they believe can be understood by using plate tectonic theory.
Doesn’t sound very interesting, but when you realise that it is a debate over how to prepare for earthquakes and how to understand the movement of the land on which we live, it starts to get a little more interesting. The competing alternative is known as thin viscous sheet theory, which says that continental interactions are best understood as the result of continuous forces across blocks of land, compared to the strain at discrete faults. In short, thin viscous sheet theory is born out of the concept that plate tectonic theory doesn’t adequately explain the smaller-scale motions of the continents.
“By describing continental deformation using plate tectonic theory, we can estimate how quickly stress is building up on major faults, which will eventually be released in earthquakes,” said Loveless, a research associate in Harvard’s Department of Earth and Planetary Sciences. “It’s this type of calculation that can have implications for seismic hazard around active faults.”
Meade and Loveless set about testing their theory by using equipment usually put to measuring small faults to gauge massive chunks of the Earth’s surface. Using highly accurate GPS data from the Tibetan Plateau, Meade and Loveless compiled an image of how fast and in what direction land in the region is moving.
“GPS data have allowed us to refine the global maps of tectonic plates and the interactions between them, giving a more detailed view of how the Earth’s crust deforms,” Loveless explained.
“If strain is localized mostly along major faults, then plate tectonic theory can also be used to describe the complex patterns of continental deformation,” said Meade.
The enormous amounts of data compiled allowed Meade and Loveless to measure down to an amazing single millimetre per year, providing them with the evidence they need to preove that the Tibetan Plateau’s geologic strain is found at the faults.
“If strain is localized mostly along major faults, then plate tectonic theory can also be used to describe the complex patterns of continental deformation,” said Meade.
Source: Harvard University
Image Source: NASA Earth Observatory
Curiously, a well written read!
In our book, This Dynamic World, we explore many theories regarding the end of the world or at least its passing from one age to the next. One of the stranger ones is the theory of pole shift. The motion picture 2012 had a lot of fun with sliding continents as a result of pole shift. It seems impossible but then we see how nicely South America and Africa appear to have fit together. What are your thoughts?