What is the name of the process that creates new oceanic crust at mid-ocean ridges?

The process that creates new oceanic crust at mid-ocean ridges is seafloor spreading.

At a mid-ocean ridge, two oceanic plates move apart. Hot mantle rises into the gap, pressure drops, and some of the mantle melts. Basaltic magma then reaches the seafloor, cools, and crystallizes into new oceanic crust. As more magma is added, older crust is pushed away from the ridge axis.

This process became a cornerstone of plate tectonics in the 1960s. Symmetrical magnetic stripes on either side of ocean ridges showed that basalt had recorded repeated reversals of Earth’s magnetic field as it formed. The matching patterns provided powerful evidence that the seafloor was spreading outward.

Seafloor spreading is not the same as continental drift, which describes the movement of continents. Subduction is almost the opposite process: at deep-ocean trenches, old oceanic lithosphere sinks back into the mantle. Erosion wears down existing rock but does not create oceanic crust.