At places where earths plates meet, and deep places within the earths rock layers, the conditions are very hot. Where do you think the heat comes from

Answer: Asthenosphere.

The rising hot rock comes in contact with cold rocks near the surface of Earth where it gives off its heat, cools, and sinks again. Most of the rock in the mantle moves in this broad cyclic flow, indicated by the arrows in the figure. This zone, where rock is soft enough to flow, is called the asthenosphere.

Explanation:

The asthenosphere is the highly viscous, mechanically weak and ductile region of the upper mantle of the Earth. It lies below the lithosphere, at depths between approximately 80 and 200 km below the surface.

The asthenosphere is a layer (zone) of Earth's mantle lying beneath the lithosphere. It is a layer of solid rock that has so much pressure and heat the rocks can flow like a liquid.

The asthenosphere is also known as the "low velocity" zone of the mantle because seismic waves slow down as they pass through it. This property tells us that the asthenosphere is composed of partially molten rock slush like material consisting of solid particles with liquid occupying spaces in between.