Two earthquakes in the same spot over a couple hundred years is not cause for alarm. But what puzzled seismologists about these tremors was that they began in relatively flat beds of the ocean — away from any faults or cracks in the Earth’s crust where tectonic plates slip past each other, releasing energy and causing earthquakes.
So what’s causing the rumbles under a seemingly quiet area? [In Photos: Ocean Hidden Beneath Earth’s Crust]
The peeling is likely driven by a water-absorbing layer in the middle of the tectonic plate, according to National Geographic. This layer might have undergone a geological process called serpentinization, in which water that seeps in through cracks causes a layer to transform into soft green minerals. Now, this transformed layer might be causing enough weakness in the plate for the bottom layer to peel away from the top layer. That peeling could lead to deep fractures that trigger a tiny subduction zone, National Geographic reported.
Originally published on Live Science.