The temperature where the lithosphere transitions into the asthenosphere would be about 600ºC to 1200ºC. That is where peridotites, or mantle rocks, start to become soft. The lithosphere is about 100 kilometers deep.
The Earth has three main layers. The innermost is the core, in the middle is the mantle, and the outermost layer is the crust, which is composed of the continents and the ocean floor. The lithosphere is made up of the crust and the brittle upper part of the mantle. The crust is broken into sections called tectonic plates. These plates are always moving, but they are doing so very slowly. When two plates collide with each other, earthquakes can happen.