Final answer:
The lithosphere does not flow because it is too brittle, composed of the crust and the upper mantle that behave as rigid solids, fracturing under stress.
Step-by-step explanation:
The lithosphere of Earth will not flow because it is too brittle. The lithosphere, defined by its mechanical properties, is composed of the crust and the uppermost mantle. Both of these layers behave as a brittle, rigid solid.
When stresses are applied to the lithosphere, it does not flow like a liquid or deform plastically; instead, it can fracture, leading to geological phenomena such as earthquakes. In contrast, the asthenosphere beneath the lithosphere is partially molten and can behave plastically, allowing it to flow.