Here's why:
* Seafloor spreading is the process where new oceanic crust is formed at mid-ocean ridges.
* Magma from the Earth's mantle rises up through these ridges.
* This magma cools and solidifies, forming basalt, a type of extrusive igneous rock.
While other types of igneous rocks can form in other geological settings, basalt is the dominant rock type found at mid-ocean ridges.
