Can the magma inside a volcano cool down?

Answer 1

Generally speaking it does not cool down. Heat is a very stubborn scientific property. When we study heat we look at a few key points:

1. Heat transfers
2. Heat radiates
3. Heat rises
4. Heat is pure energy
5. Heat gradually fades when the source is removed.

In a Volcano all the magma is at a consistent temperature, that is it's in it's purest energy state when it's constant. If an object falls inside or the magma comes out (lava) the object or lava will eventually transfer heat to near by objects thus cooling itself down or equalizing it's temperature.

Let's look at an example:

If you bring a pan of water to a rapid boil (temperatures are at or exceed 212F or 100C) and add a cup of cold water, the boiling will stop as you've changed the temperature of the water. Hot + Cold = Warm. Now, If you're to remove it from it's heating source the temperature the water is at would remain constant before dropping. If you're to continue the source of heat the water would continue to raise in temperature before returning to a boil.

The same property applies to Volcano's. Unless you add a massive amount of colder fluid the temperature of the magma would remain constant. Generally an object that falls in (stone, metal, etc) would not cool the magma. The magma would instead transfer or radiate the heat from itself to the object that came in contact thus changing the objects temperature not itself.

Answer 2

Yes, the magma inside a volcano can cool down and solidify, forming igneous rock. This can happen if the volcano becomes dormant or if the magma gets trapped underground without erupting.