According to plate tectonic theory, plates can be made up of.

According to plate tectonic theory, the Earth's lithosphere, which is the rigid outer layer of the Earth, is divided into several large and small tectonic plates. These plates can be made up of:

1. Continental Crust: This crust is less dense and typically thicker than oceanic crust. It forms the continents and large landmasses on Earth.
2. Oceanic Crust: Oceanic crust is thinner but denser than continental crust and primarily lies beneath the ocean basins. It is mainly composed of basaltic rock.

Both types of crust - continental and oceanic—form the composition of tectonic plates. These plates float on the semi-fluid asthenosphere, a semi-molten layer below the lithosphere, and interact with each other at their boundaries, resulting in various geological phenomena such as earthquakes, volcanic eruptions, and the creation of mountain ranges.