The Mid-Oceanic Ridge is composed mainly of basaltic igneous rock. This rock is formed from the cooling and solidification of magma that erupts from the ridge's central rift valley.

Here's a breakdown:

* Basalt: A dark-colored, fine-grained volcanic rock that is rich in magnesium and iron. It is the most common rock type found on the ocean floor.

* Igneous: Rocks formed from the cooling and solidification of molten rock (magma or lava).

The Mid-Oceanic Ridge is a massive underwater mountain range that runs along the entire length of the Earth's oceans. It is the site of seafloor spreading, where new oceanic crust is created as magma rises from the Earth's mantle and cools.