Here's why:
* Basalt is the most common rock type found in the oceanic crust. It forms from the cooling and solidification of magma erupted at mid-ocean ridges.
* Oceanic crust is primarily composed of mafic minerals, which are rich in magnesium and iron. Basalt is a mafic rock.
* The chemical composition of basalt closely matches the average composition of oceanic crust. This includes elements like silicon, oxygen, iron, magnesium, calcium, and aluminum.
While other rock types exist in the oceanic crust, like gabbro and peridotite, basalt is the dominant and representative composition.
