During a convergent collision, the two plates move towards each other, as a result of which the denser plate sinks below the lighter plate. It results in the formation of a subduction zone marked by the trench above it and also leads to the uprising of magma to the surface forming volcanoes.
In the case of a convergent plate boundary between an oceanic and a continental plate, the continental shelf forms along the edge of the continental margin whose slope gradually declines towards the colliding boundary.
The subdustion zones between the oceanic tectonic plates and continental tectonic plates go in both ways when it comes to the lithosphere. They are both destructive and constructive. With the subduction zone occurring, the crust from the oceanic plate gets into the mantle, gets melted, and thus destroyed. On the other hand, this type of boundary enables the magma from the mantle to penetrate through the crust and reach the surface. As the magma reaches the surface, it starts to create volcanoes, be it in the form of island arcs or continental arcs. The volcanoes then release lot of lava from them on the surface, and this lava cools off and creates new layers of rock. The uplifting volcanoes, as well as the push of the plate that subducts, results in creating a shellow and relatively flat part of the ocean which is alongside the coastline. This shallow and flat part of the ocean is known as continental shelf. The continental shelf is the part of the ocean that has the warmest water, the light penetrates through all of its waters, and it is the most abundant in life. It depth is relatively small.
