Most of the world's volcanoes are associated with subduction zones, according to SanAndreasFault.org. Subduction zones encircle the Pacific Ocean, forming the Ring of Fire, the region where nearly all the volcanoes in the world occur. A subduction zone is the place where a tectonic plate has moved beneath another.
Most volcanoes are relatively predictable and only occur along the edges of tectonic plates. Volcanoes can also occur at midocean ridges, but they are still related to plate activity. However, volcanoes can also occur randomly around the globe. These random volcanoes are called hot-spot volcanoes. It is still unknown if hot-spot volcanoes relate to tectonic plates, as explained by Penn State researchers. Several occur on midocean ridges, but whether this is a coincidence or not is still debated by scientists.
Hot spots develop above mantle plumes, according to Oregon State University researchers. The hot spot generates magma, which can rise to produce an active volcano. There are hot-spot volcanoes in Africa, one in Yellowstone National Park in North America and one in Hawaii, just to name a few. While they do seem to occur randomly, hot-spot volcanoes still tend to appear in places that already have volcanic activity, such as along the edges of the Ring of Fire.