Why is the greatest temperature change in the asthenosphere?

The greatest temperature change in the asthenosphere occurs because it is located beneath the lithosphere, where temperatures increase with depth due to geothermal gradient. The asthenosphere is partially molten and experiences significant heat from the Earth's interior, contributing to its plasticity and ability to flow. Additionally, tectonic processes, such as subduction and mantle convection, can further enhance temperature variations within this layer.