Why does high pressure raise the temperature of rock to liquify it into motion like water?

454 views

[ad_1]

How can rock molecules squeezed tighter together behave like liquids with molecules spread farther apart? Usually when heat liquefies a solid such as ice, the molecules become less dense and spread more apart the higher the temperature gets.

Yet the rock behaves as though its molecules are spread apart when instead it’s crushed together under hundreds of kilometers deep into the Earth.

**Bonus** 2 questions if anyone else can get to them:

The molten rock even rises and sinks like water when different in temperature or density, but that seems like an oxymoron under those immense pressures because the only way for higher temperature rock to rise like a liquid with spread out molecules is for the rock to be more crushed together by higher pressure.

Can enough pressure make the rock become a gas like air?

In: Chemistry
[ad_2]

> How can rock molecules squeezed tighter together behave like liquids with molecules spread farther apart?

Because it is really hot! More pressure does raise the melting temperature of most substances, stone included, but the interior of the Earth is hot enough.

> but that seems like an oxymoron under those immense pressures because the only way for higher temperature rock to rise like a liquid with spread out molecules is for the rock to be more crushed together by higher pressure.

This question seems to be based on the premise that the rock is hot *because* it is under pressure. That isn’t correct at all, being under pressure doesn’t create heat. *Compression* concentrates heat and raises the temperature, but that is just part of why the core heated up long ago.

Near the core the stone heats up and becomes slightly less dense, causing it to rise and circulate via convection.

> Can enough pressure make the rock become a gas like air?

No, pressure makes things more dense. Higher pressure could make it solid at that same temperature, or higher temperature could make it a gas at those pressures.