At an ocean-continent or ocean-ocean [1] convergent boundary, oceanic crust is pushed far down into the mantle (Figure 4.4b). It also extracts the so-called incompatible elements, which don't fit into mantle minerals and move into the liquid melt. What is the difference between Oceanic and Continental Crust? The balance is not perfect: 0ceanic crust starts of different in composition from the mantle and all that brine it interacted with caused many chemical changes. This water rises into the overlying mantle where it contributes to flux melting of the mantle rock. Examples of such rocks are those in Quebec, Canada which are estimated to be about 4 billion years old. Continental crust tends to be much older than the oceanic kind, and rocks found on this kind of crust are often the oldest in the world.

In an oceanic to continental plate collision, it's the oceanic plate that will subduct because of its higher density. The effective viscosity is defined by the minimum of the two components from equation and : (3) η eff = m i n (η viscous, η yield) Partial melting generates basaltic oceanic crust and a complementary depleted residue. Oceanic crust tends to be denser and thinner than continental crust, so the denser oceanic crust gets bent and pulled under, or subducted, beneath the lighter and thicker continental crust. Oceanic crust, being so thin, is a very small fraction of the Earth -- about 0.1 percent -- but its life cycle serves to separate the contents of the upper mantle into a heavy residue and a lighter set of basaltic rocks. At some convergent boundaries, an oceanic plate collides with a continental plate. This forms what is called a subduction zone. Like the oceanic crust, the continental crust is destroyed by the subduction process but goes through more partial melting processes than the oceanic crust, allowing it to maintain its lower density and remain above the ocean. The crust returns changed and can’t just turn back into peridotite – it stays as something more interesting. At some convergent boundaries, an oceanic plate collides with a continental plate. The oceanic crust, which, on average, is only about six kilometers thick, is primarily made up of the igneous rock basalt. This forms what is called a … Composition of Oceanic Crust. It is heated up, and while there isn’t enough heat to melt the subducting crust, there is enough to force the water out of some of its minerals. At each time step, the temperature in each cell is compared to the solidus temperature. Oceanic crust is created from the mantle and returns there to be destroyed. Oceanic crust tends to be denser and thinner than continental crust, so the denser oceanic crust gets bent and pulled under, or subducted, beneath the lighter and thicker continental crust.