* Seafloor Spreading: New oceanic crust is continuously being formed at mid-ocean ridges. As tectonic plates pull apart, magma rises from the mantle, cools, and solidifies, creating new crust. This process is known as seafloor spreading.
* Subduction: Older oceanic crust is constantly being recycled back into the mantle through subduction. This happens at convergent plate boundaries, where one plate slides beneath another. The denser oceanic crust dives beneath the lighter continental crust, melts back into the mantle.
In summary:
* Continuous creation: New oceanic crust is constantly being created at mid-ocean ridges.
* Continuous destruction: Old oceanic crust is continuously being destroyed at subduction zones.
This continuous cycle of creation and destruction means that the oldest oceanic crust is much younger than the oldest continental crust. The oldest oceanic crust is about 200 million years old, while the oldest continental crust is over 4 billion years old.
