1. Decompression Melting: This occurs when rock is brought closer to the Earth's surface. As pressure decreases, the melting point of the rock also decreases, allowing it to melt. This is a major process at mid-ocean ridges and hotspots where tectonic plates pull apart.

2. Addition of Water: Water lowers the melting point of rocks. When water is added to rocks, it can trigger melting, even if the rock is not under immense pressure. This is common in subduction zones where water-rich sediments are carried down with the descending plate.

3. Heat Transfer: Magma can be generated when hot, molten rock from deeper in the Earth comes into contact with cooler rocks. This transfer of heat can melt the surrounding rock, creating new magma. This occurs in areas with active volcanism, like the Yellowstone Caldera.