Flexi Says: When oceanic crust collides with a continent, an oceanic-continental convergent boundary forms. The oceanic plate is denser, so it undergoes subduction. This means that the oceanic plate sinks beneath the continent, forming a deep ocean trench. As the oceanic plate sinks, the heat causes rock to melt, forming magma that rises through the overlying continental crust. This forms a line of volcanoes known as a continental arc. Earthquakes also occur due to the motion of the colliding plates and rising magma plumes.