Why is the continental crust older than the oceanic crust?
Continental crust is almost always much older than oceanic crust. Because continental crust is rarely destroyed and recycled in the process of subduction, some sections of continental crust are nearly as old as the Earth itself.
Why does the continental crust sit up higher than the oceanic crust above the mantle?
Over time, oceanic crust cools, and therefore its density increases. At this point the old oceanic crust is cool enough that its density is higher than the mantle it sits on top of, so once it starts to bend it continues to sink into the mantle in a process called subduction.
Why does oceanic crust Subduct down under the continental crust back into the mantle?
Subduction is possible because the cold oceanic lithosphere is slightly more dense than the underlying asthenosphere, the hot, ductile layer in the upper mantle underlying the cold, rigid lithosphere. Once initiated, stable subduction is driven mostly by the negative buoyancy of the dense subducting lithosphere.
Why does continental crust float on the surface of the mantle?
If you know Earth’s density, they are too buoyant to sink compared to the heavier mantle rocks underneath. This is why continental crust floats on the surface of the mantle. Continental crust also consists of the shallow seabed close to shores called continental shelves.
How is continental crust different from oceanic crust?
But continental crust is completely different than oceanic crust. Continental crust is thicker and less dense than oceanic crust. It’s too buoyant to sink compared to the heavier mantle rock underneath. Because continental crust floats on the surface of the mantle, continents can have rocks over 4 billion years old.
How old is the crust compared to the mantle?
It’s too buoyant to sink compared to the heavier mantle rock underneath. Because continental crust floats on the surface of the mantle, continents can have rocks over 4 billion years old. . As we move down through the crust into the mantle, we get into denser and heavier rocks. It’s not only density. But the further we go, the hotter it becomes.
How is the continental crust produced and destroyed?
Continental crust is produced and (far less often) destroyed mostly by plate tectonic processes, especially at convergent plate boundaries. Additionally, continental crustal material is transferred to oceanic crust by sedimentation.
https://www.youtube.com/watch?v=sw9m8JxYtGE