Final answer:
The Earth's outer core is hotter than the mantle, with the core consisting mainly of molten iron at temperatures around 2,500°C, compared to the mantle's solid rock composition.
Step-by-step explanation:
In comparing the temperatures of the Earth's mantle and the outer core, it is clear that the outer core is hotter than the mantle. The reason for this is that the mantle, which has a thickness of about 2,900 kilometers, is composed of relatively solid rock that can deform and flow slowly due to the temperatures and pressures found there. In contrast, the Earth's outer core is primarily made up of molten iron at a temperature of around 2,500°C. This liquid state of the outer core, combined with its composition mainly of iron and some nickel, indicates that it is indeed hotter than the solid rock of the mantle.