Final answer:
Oceanic crust is more dense than new oceanic crust because of a process called compaction.
Step-by-step explanation:
The oceanic crust is more dense than new oceanic crust because it has undergone a process called compaction.
During compaction, the previously formed oceanic crust undergoes a process in which the sediments, minerals, and rocks are compressed under the weight of overlying material. This compression increases the density of the oceanic crust.
As a result, the older oceanic crust becomes denser and sinks into the mantle, creating basins, while new oceanic crust is less dense and sits on top of it.