Final answer:
The "rigid" tectonic plates compose the lithosphere, which is the outermost layer of the Earth's surface.
Step-by-step explanation:
The "rigid" tectonic plates compose the lithosphere. The lithosphere is the outermost layer of the Earth's surface, consisting of the crust and a portion of the upper mantle. It is divided into several large and small pieces called tectonic plates that float on the semi-fluid asthenosphere beneath.
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