The hottest layer of the Earth is the inner core, which is a solid ball of iron and nickel with temperatures estimated to be between 5,200°C (9,392°F) and 6,000°C (10,832°F).

Here's why:

* Pressure: The immense pressure from the weight of all the layers above crushes the inner core into a solid state despite the extreme heat.

* Radioactive decay: The inner core contains radioactive elements that decay and release heat.

While the outer core is also very hot (around 4,500°C or 8,132°F) it's a liquid layer due to the lower pressure compared to the inner core.