Lecture9

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• Why does temperature increase with depth?
• Earth cools to space by radiative processes.
• Heat conducts outward from the core into the lower mantle.
• Rocks must heat up when pressure increases.
• When any type of matter is compressed, the heat within is distributed over a smaller volume. So while the "amount" of heat is the same, there is more of it relative to the compressed size.
• Compressive heating is how a diesel engine works.
• Conversely, expanding gas cools (like an aerosol can spraying, the basic principle of air-conditioners).

8.5 How hot is the interior of Earth?