Final answer:
Oceanic plates rift apart due to continental rifting, where a continental mass splits apart and creates two separate landmasses that drift away from each other. This process is driven by upwelling currents in the mantle and results in the formation of new ocean floor along the rift zones.
Step-by-step explanation:
Plates can rift apart in the ocean due to the process of continental rifting. This occurs when a continental mass splits apart, creating two separate landmasses that drift away from each other. As the landmasses separate, new ocean floor is created along the rift zone.
Molten rock rises from below to fill the space between the receding plates, forming basaltic lava that becomes the oceanic crust. The separation of oceanic plates is driven by upwelling currents in the mantle, which push them apart along the rift zones. This process is responsible for the formation of new ocean basins and contributes to the continuous renewal of the oceanic crust over geological time.