Which layer of the Earth's mantle is characterized by low resistance to plastic flow and convection?

The asthenosphere is the layer of the Earth's mantle that is characterized by low resistance to plastic flow and convection. This layer lies beneath the lithosphere and extends to about 700 kilometers deep. It is composed of partially molten rock, which allows it to deform and flow slowly over geological timescales. The reduced viscosity in the asthenosphere facilitates the movement of tectonic plates located above it, making it crucial for plate tectonics.

In contrast, the lithosphere is the rigid outer layer of the Earth, composed of the crust and the uppermost part of the mantle. It is not capable of the same plastic flow or convection due to its solid nature. The mesosphere, located below the asthenosphere, is more rigid and does not exhibit the same low resistance to flow. The inner core, being the innermost solid layer of the Earth, is also not involved in plastic flow or convection due to its solidification and extreme density. Therefore, the asthenosphere's unique properties make it essential for understanding the dynamics of the Earth's interior and tectonic processes.