Convergent Boundaries
Converge is Basically two objects that come together, in the case of plates of plate tectonics two pieces of the earths crust come together. As these two plates push against each other and one is pushed and the other. When this happens near land we see the two rising plates which form mountain ranges. A parallel oceanic trench typically forms off the shore.
Oceanic Crust Formation
Oceanic Crust is the outermost layer of the earths lithosphere and it is found under the ocean. It is about 4 miles thick. New crust is formed under the ocean because of sea floor spreading. Magma from the mantle which follows a pattern of convection currents which is a complete rotation is constantly doing this which comes to the surface and then it goes up to the crust and after it hits the crust it rolls back down to the bottom if the mantle and then as it is rolling back down it move the crust along with it. Which causes the oceanic crust to move or spread also known as Sea Floor Spreading.
Continental Crust Formation
The thickest portions of continental crust in found in various mountain ranges , the crust is about 22 miles thick. Continental is lighter than oceanic crust having a density of about 2.7 grams per cubic centimeter. Oceanic and continental rocks are different from each other in age. All the earths continents have a core that's made of old granite, gneiss, schist, sedimentary, volcanic rocks. The core foundation is usually referred to a shield or basement rock. In Canada rocks have been discovered to be 3.96 billion years old! The crust is made by melting mantle. The magma in the mantle is denser than the other material so it floats up and because of the oxygen located in our atmosphere, it cools and forms crust. That's how crust is formed in some parts of the world.In other parts of the world, such as Hawaii volcanoes form in the pacific plate. The magma which erupts form the volcano the magma cools and a couple hundred years after the magma has cooled, it creates mid-ocean ridges which are big enough to see over the sea floor surface and support life.