The continent-sized slabs you're describing are called tectonic plates.

Here's a breakdown:

* Tectonic plates are large, irregularly shaped pieces of the Earth's lithosphere, which is the rigid outermost layer made up of the crust and upper mantle.

* These plates are constantly moving, driven by convection currents in the mantle beneath them.

* The interaction of these plates at their boundaries is responsible for major geological events like earthquakes, volcanic eruptions, and mountain formation.

Let me know if you have any other questions about tectonic plates!