What process adds new oceanic crust to the ocean floor?

Sea-floor spreading is the process responsible for adding new oceanic crust to the ocean floor. This phenomenon occurs at mid-ocean ridges, where tectonic plates are moving apart. As the plates separate, magma from the mantle rises to fill the gap. When this magma cools and solidifies, it forms new oceanic crust. This process not only increases the size of the ocean floor but also creates new geological features like underwater mountains and ridges.

In contrast, subduction involves one tectonic plate sinking beneath another, leading to crust being recycled rather than created. Continental drift refers to the slow movement of continents across the Earth's surface but does not specifically address the formation of oceanic crust. Basalt formation describes the type of rock that forms from the cooling of the magma but does not directly explain the process of adding crust to the ocean floor. Thus, sea-floor spreading is the most fitting answer to describe the continuous creation of new oceanic crust.