What layer of the Earth is characterized as weaker and liquid?

The asthenosphere is characterized as a weaker and semi-fluid layer located beneath the rigid lithosphere. This region extends from the upper mantle, approximately 100 to 200 kilometers deep, and is composed of partially molten rock that allows for the movement of tectonic plates. The viscous nature of the asthenosphere facilitates convection currents, which play a crucial role in plate tectonics and contribute to the dynamic processes of the Earth's crust.

In contrast, the lithosphere is rigid and comprises the uppermost portion of the mantle and the Earth's crust. The mesosphere, found beneath the asthenosphere, consists of denser, more solid materials and behaves in a more rigid manner. The Earth's core, while liquid in its outer section, is mainly composed of iron and nickel and exhibits different characteristics than the asthenosphere. Thus, the asthenosphere’s unique properties of being weaker and partially molten set it apart from the other layers of the Earth.