What makes Earth’s core hot? Why isn’t it just a cold blob made up of metal and minerals?
In: Earth Science
There are many different factors for this:
1. Surface area to volume ratio: The bigger an object, the slower it cools because it has only so much surface area from which heat can dissipate. The earth, just by virtue of its size, still retains heat from its formation 4 billion years ago.
2. Once the earth cooled enough, its outer layer solidified into the crust (rock), which is an excellent insulator and made it even harder for heat to escape, effectively acting as a blanket.
3. Earth is surrounded by a vacuum where you can only lose heat via radiation. This is extremely inefficient and takes an insanely long amount of time. It’s also the same reason why people don’t freeze instantly when exposed to outer space.
4. The tidal force that the moon exerts on the earth converts earth’s rotational energy into heat and warms the interior. This process is called tidal heating. A good example would be Jupiter’s moon Io. When the moon was young, an earth day was just 6 hours long, meaning it was spinning 4x as fast. Now, all these years later, all that energy has been converted, and continues to be converted, into heat.
5. The earth has a lot of radioactive elements in the core which decay and release energy, warming up the other layers.
Now not all of these factors contribute equally and perhaps some play a much bigger role than others, but yeah, because of all of them, even after all these years, the earth’s core is still hot.
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