Mid-ocean ridges are made up of Igneous rock k/a Mid-ocean Ridge basalt rock.
Explanation:
The cooling and crystallization of magma and ocean ridges result in the formation of the new crust of igneous rocks. The tectonic plates on the lithosphere layer of the earth keep moving, a divergent boundary is formed when tectonic plates move which may cause an earthquake or oceanic crust.
Mid-ocean crusts are mid-water mountain ranges formed by plate tectonics. A new seafloor and oceanic lithosphere are formed due to the tectonic plate divergent. This seafloor is made up of igneous rocks.