The Philippine Islands are located right on a convergent plate boundary. This plate boundary is a subduction zone, and is the cause for numerous volcanoes throughout the islands, and the frequent earthquakes. A subduction zone is where two tectonic plates collide, and due to densitiy differences, one is pushed beneath the other. This usually happens with an oceanic plate and a continental plate colliding, because they both are different densities. In the Philippines, it is the South China Sea oceanic plate that is being forced downward.

The reason there are volcanoes is because the plate that is forced downward is put under intence pressure, and melting occurs. The melted rock can rise up to the surface and cause a volcano to form.