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Name: Alfred
Grade: 6-8
Location: FL
Country: USA
Date: Spring 2011

Why is the inner core the hottest layer? How is that possible?

There are two factors causing the center of the Earth hotter than various layers of the Earth's. First, the more dense is the layer. The denser layer, the hotter it will be. In addition, the source of the heating is due to heat produced by nuclear decay. These substances tend to be more dense than lower dense substances. So the source of heat (temperature) is higher, the greater will be the temperature.

Having said all that, the reasons are rather more complicated in the "real" Earth. If the inner layers were less dense they would rise (bubble) to the "surface" leaving the inner layers more dense and thus hotter layers.

Vince Calder


The inner core of the Earth is the hottest because of the enormous amount of pressure.

You can try an experiment at home to prove that pressure will raise the temperature of an object. You'll probably want to wear gloves so that you do not hurt your fingers and have a parent help you out. Take a very thin wire, or possibly some dental floss. Next, get an ice cube out and then try pull the wire through the ice cube. Putting the ice cube on the edge of a counter might work best so that you have room on the sides of the ice cube to be able to pull down. What you should see is that putting the pressure on the ice cube will melt the ice around where the wire is. If you keep at this, you can eventually pull the wire into the middle of the ice cube and have the section above the wire refreeze so that the wire is going right through the middle of the ice cube!

Now, think about how much pressure there must be in the core of the Earth given the weight of all of the dirt and rock on top of it. The center of the Earth is made of iron and it is so hot, in fact, that the iron is liquid!

Matt Voss

The temperature of the inner core of the Earth is believed to be due to radioactive decay of radioactive elements. Plus the gravitational attraction of the heavier, that is more dense, elements. So the source of heat is the center of Earth (more or less). These sources combined, are much hotter than the surrounding upper, and less dense, layers of Earth's makeup. That is why volcanoes give us a glimpse of what is "going on" deep in Earth's makeup.

Vince Calder

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