11.   Continental lithosphere stands higher than oceanic lithosphere because continental crust is both of greater thickness and lower density than oceanic crust.

12.   Like the oceanic crust, continental crust has a layered structure, but one which is much more complex and less clearly defined.

13.   This proposed that mid-oceanic ridges represent regions where new oceanic crust is being generated by the upwelling of hot mantle material.

14.   Further corroborative evidence was provided by the palaeomagnetic record of ocean sediments containing particles of iron-rich minerals which lay on the basaltic oceanic crust.

15.   It appeared that these offsets marked some kind of lateral movement between adjacent sections of oceanic crust.

16.   Oceanic crust has a layered structure which shows remarkably little disturbance and this would not be the case if significant deformation had occurred.

17.   Wedges of oceanic crust are thrust up on to the overlying sediments of the subduction zone and uplift ensues.

18.   Alternatively, subducted oceanic crust may be able to pull adjacent continental crust down into the asthenosphere.

19.   Salients of oceanic crust may be left along the suture zone and parts of the Mediterranean Sea represent remnant ocean basins formed in this way.

20.   The terranes are of several types and include slivers of oceanic crust, fragments of intra-oceanic island arcs and slices detached from unknown continental margins.