The Ring of Fire's volcanoes are formed by subduction. This is a process where one tectonic plate slides beneath another.

Here's a breakdown:

* Tectonic Plates: The Earth's surface is made up of massive plates called tectonic plates that are constantly moving.

* Subduction Zones: In the Ring of Fire, the denser oceanic plates are pushed beneath the less dense continental plates or other oceanic plates at what are called subduction zones.

* Melting and Magma: As the oceanic plate descends, it melts due to the intense heat and pressure in the Earth's mantle. This molten rock, called magma, is less dense than the surrounding rock and begins to rise.

* Volcanic Eruptions: The magma eventually reaches the surface, erupting as volcanoes.

The Ring of Fire is characterized by a chain of volcanoes along the boundaries of the Pacific Plate where subduction is active.