“Never heard of it before, but applying 20/20 hindsight, with everything that goes on inside the earth, tectonic movements, magma convection, crust heaving and bending from tidal forces, ocean waves and whatnot, it would be more surprising if the earth was completely silent”.
Thread Winner!
Keep in mind that we are spinning.
The core is spinning at a different rate than the crust.
The solar system is spinning.
The Milky Way Galaxy is spinning.