Old Discontinuity Planes

[Proteus]

Are there any old tectonic discontinuity planes known to exist, ie, which have stopped playing part in tectonic activity, and if so, where?

[markhaldane]

Do you mean fault planes? If so, then yes; faults which are no longer tectonically active are very common.

 

In geology the term "discontinuity" is used to describe the boundaries between layers in the Earth's interior where the velocities of seismic waves change. For example, the boundary between the crust and the mantle is known as the Mohorovičić discontinuity, and is defined by an increase in seismic wave speed (mainly P-waves I think). There is no "tectonic" activity at these boundaries.

[Proteus]

My bad. I did read discontinuity planes to mean whatever it is called that I meant, but it was Dutch. Perhaps the term is different in English. They're apparently called plate boundaries. In particular, I wondered if there were old plate boundaries over Siberia, and if there were between England and Norway.