Which term refers to a rigid section of the lithosphere that moves over the asthenosphere?

The term "plate" refers to the rigid sections of the lithosphere that move over the underlying, more malleable asthenosphere. The lithosphere is composed of the Earth's crust and the uppermost part of the mantle, which together form these tectonic plates. These plates float and glide on the semi-fluid asthenosphere beneath them due to convection currents and other geological processes.

This concept of tectonic plates is fundamental in understanding plate tectonics, which explains the movement of continents, the formation of mountains, and various seismic activities such as earthquakes. Recognizing that these plates are rigid and defined sections helps provide clarity about their interactions at plate boundaries, including convergent, divergent, and transform boundaries.

The other terms, while related to geological processes, do not specifically describe the rigid sections that move in the context of plate tectonics. The crust is part of the lithosphere but does not encompass the entire moving section. A shell generally refers to a hard outer casing and does not apply specifically to the Earth's structure. Likewise, a stratum refers to layers of sedimentary rocks but does not pertain to the movement and rigid nature of tectonic sections.