Why do you think oceanic crust is young while continental crust is mostly old?
1 Answer
New crust is formed at the mid ocean ridges. Old oceanic crust is most often destroyed at subduction zones. Continents are old crust that has been separated by a divergent boundary
Explanation:
Mid Ocean ridges are the source of new crustal material. It is thought that convection currents brings fresh magma to the surface at the divergent boundaries The youngest part of the world crust is found in oceanic crust next to the mid ocean ridges.
Generally Oceanic crust is destroyed at subduction zones. The oldest Oceanic crust is pushed and pulled underneath continental crusts which destroys the Oceanic Crust while the continental crust survives. This means that Oceanic crust can grow seriously old as it will be destroyed at the convergent boundaries.
How very old sedimentary layers end up in horizontal layer on the continents is a mystery given what is now known about plate tectonics. It is clear that continental crust is rarely distroyed at convergent boundaries. This means that continental crust is almost always older than Oceanic crust.
