Here's why:

* Large: Tectonic plates are massive, covering vast areas of the Earth's surface.

* Brittle: The Earth's outer shell, known as the lithosphere, is composed of the crust and the uppermost part of the mantle. This layer is rigid and brittle, capable of breaking and fracturing.

* Pieces: Tectonic plates are like giant puzzle pieces that fit together and move slowly over time.

* Earth Outer Shell: Tectonic plates make up the Earth's outer shell, the lithosphere.

The movement of these plates is responsible for many of the Earth's geological features, including:

* Earthquakes: When plates slide past, collide with, or pull apart from each other, they can cause earthquakes.

* Volcanoes: Volcanoes often form at plate boundaries, where magma from the Earth's mantle rises to the surface.

* Mountain Ranges: Collisions between tectonic plates can force land upwards, creating mountain ranges.

* Ocean Trenches: Where plates collide, one plate can be forced under the other, creating a deep trench in the ocean floor.

Let me know if you have any other questions!