* Seafloor Spreading: At divergent plate boundaries, magma rises from the mantle and erupts, creating new oceanic crust. This process is called seafloor spreading.
* Conveyor Belt Analogy: Imagine a conveyor belt with new crust being added at one end. As the belt moves, the older crust gets pushed away from the "addition point," which is the divergent boundary.
* Isochron Maps: Scientists use radiometric dating of rocks to determine the age of different parts of the ocean floor. These data points, when plotted on a map, reveal a pattern of concentric bands of increasing age moving away from the mid-ocean ridge (the site of the divergent boundary).
Therefore:
* The youngest oceanic crust is found at the mid-ocean ridge, the site of the divergent plate boundary.
* As you move away from the mid-ocean ridge, the age of the crust increases because it has been moving away from the site of new crust formation for a longer time.
Important Considerations:
* Rate of Spreading: The rate at which the plates move apart influences the age-distance relationship. Faster spreading rates result in wider bands of younger crust.
* Subduction Zones: Oceanic crust eventually gets subducted back into the mantle. Therefore, the oldest oceanic crust is rarely found on the surface, as it has likely been recycled.
In summary, the age of oceanic crust is a direct indicator of how far it has moved away from the divergent plate boundary where it was formed.
