Fault lines are:

the crust of the athenosphere that has fractured along plate boundaries and ridges
the crust of the lithosphere that has fractured along plate boundaries and ridges
the crust of the kryosphere that has fractured along plate boundaries and ridges
the crust of the biosphere that has fractured along plate boundaries and ridges

1 answer

Fault lines are best described as:

the crust of the lithosphere that has fractured along plate boundaries and ridges.

The lithosphere is the rigid outer layer of the Earth, which includes the crust and the upper mantle. Faults are fractures in this layer where there has been movement of the rocks on either side.