asthenosphere
Dense oceanic crust slides under less dense continental crust
A strike-slip fault generally occurs at a transform boundary
high pressure
The weight of the rocks in the crust and upper mantle results in the pressure that allows diamonds to form.
refraction
The weight of the rocks above the mantle results in high pressure.
Diamonds need high temperatures and pressure to form from carbon. Diamonds form in the mantle in certain zones where conditions are right for them to do so.
There just happens to be the right critical temperature-pressure-mineral environment in the mantle in certain zones for their formation.
high presure and heat
The south pole of one magnet is attracted to the north pole of the other magnet.
compass magnets can be deflected by earths magnetic field or other permanent magnets
mantle
The continental crust is up to 70 km thick.
earth moon
At ocean ridges
magnetic stuff...