#plateboundaries

-Convection currents cause oceanic and continental crust to converge

-Oceanic crust is subducted beneath continental crust because it is denser

-Friction between the two plates causes deep focus earthquakes to occur in the Benioff Zone

-Friction created by the descending slab of ocean floor also generates enormous heat which causes partial melting of the crust

-This newly created magma is less dense than the rest of the magma and so rises and escapes through fissures in the lithosphere to form composite volcanoes

-Continental crust is also compressed into fold mountains