Here's why:

* Rock Composition: Rocks contain various minerals, and some of these minerals are rich in volatile elements like water (H₂O), carbon dioxide (CO₂), sulfur dioxide (SO₂), and others.

* Melting Process: As the rock heats up and melts, the pressure inside the rock decreases, allowing these volatile elements to escape as gases.

* Volcanic Activity: These gases are often released during volcanic eruptions, contributing to the explosive nature of some eruptions.

In addition to gases, the melting process also releases:

* Heat: Melting rocks requires a significant amount of heat energy.

* Pressure: The molten magma exerts pressure on its surroundings, which can contribute to geological events like earthquakes.

So, while the primary release is gases, the melting of rock also involves the release of heat and pressure.