* Water lowers the melting point: Water acts as a flux, which means it helps break down the chemical bonds within the rock. This makes it easier for the rock to melt at a lower temperature.

* Pressure also plays a role: The presence of water in the rock also increases the pressure within the rock. This pressure can also contribute to lowering the melting point.

Think of it this way: Imagine trying to melt a block of ice. It takes a lot of heat to do it. Now, imagine adding a small amount of salt to the ice. The salt will lower the freezing point of the water, making it melt at a lower temperature. The same principle applies to rocks, but with water acting as the "salt."