It is the sort of topography that one would expect in a region where grinding tectonic plates beneath the sea are relentlessly pushing up a crazy quilt of irregular mountains.
The whole sentence has ambiguity. What is exact meaning of it?
Seems clear enough.
The region being discussed is of the geological formation that is expected when the underlying tectonic plates of the Earth's surface are constantly in movement, and as a result new mountain ranges are forced up from the overlying surface material.