when two tectonic plates collide, the oceanic crust usually subducts beneath the continental crust. why is this so?

When two tectonic plates collide, the oceanic crust usually subducts beneath the continental crust because the oceanic crust is denser and thinner than the continental crust. Oceanic crust is typically composed of basalt and gabbro, which makes it denser (about 3.3 g/cm³) compared to the continental crust, which is thicker and composed mainly of less dense granitic rocks (about 2.5 g/cm³). Due to this density difference, the denser oceanic crust sinks beneath the more buoyant continental crust during a collision, leading to subduction. The process involves the oceanic lithosphere being forced down into the mantle at the subduction zone, creating deep ocean trenches and sometimes volcanic activity as magma forms from melting of the subducted plate material. In contrast, continental crust resists subduction because of its lower density and greater thickness, causing it to remain on top and often leading to mountain formation where the plates collide. Thus, the core reason for the oceanic crust subducting beneath the continental crust is primarily the density and buoyancy differences between the two types of crust.