Convergent boundaries happen when two pieces of Earth’s crust move together. The three types of convergent boundaries are; ocean to continental crust; ocean to ocean crust; and continental to continental crust.
Ocean to Continental Crust: Ocean to continental crust boundaries create a subduction zone where ocean crust is pushed under continental crust. Continental volcanic Arcs are formed on land such as the Andes mountain range.
Ocean to Ocean: Ocean to ocean crust also has one piece of ocean crust pushing under another piece of ocean crust because of density differences (one piece of ocean crust is less dense than the other to cause this).
This action causes Volcanic Island Arcs such as the Aleutian Island chain .
Continent to Continent: Continent to Continent crust occur with the convergence of two continental plates. This causes large folded mountain ranges such at the Alps and the Himalayan mountain ranges. Continental crust can never subduct.