The major rock type that covers most of the Earth's surface is igneous rock.

Here's why:

* Oceanic Crust: The majority of the Earth's surface is covered by oceans, and the ocean floor is primarily made of basalt, a type of igneous rock.

* Continental Crust: While continents are mostly made of sedimentary rocks, the foundation beneath them is still largely igneous rock, such as granite.

While sedimentary rocks are more visible on the surface, igneous rocks form the base of both continents and oceans.