When rock melts at calderas and is forced toward the crust, it is forced as magma.

Here's why:

* Calderas: Calderas are large volcanic craters formed by the collapse of the ground above a magma chamber.

* Magma: Magma is molten rock found beneath the Earth's surface.

* Eruption: As magma rises and accumulates beneath the surface, pressure builds. Eventually, this pressure can overcome the strength of the surrounding rock, causing an eruption. The magma then flows out as lava.

So, the process is:

1. Melting: Rock melts at a caldera, forming magma.

2. Buoyancy and Pressure: The magma is less dense than the surrounding solid rock, causing it to rise due to buoyancy. The rising magma also creates pressure.

3. Forcing: The magma is forced toward the crust, pushing against the overlying rocks.

Let me know if you have any other questions!