The pacific ring of fire is an area of earth that is extremely volcanically active and has a high incidence of earthquakes. The pacific ring forms an arc that stretches from South America up to North America, across to Asia and down to New Zealand. The reason that so many earthquakes and volcanoes happen along this path is because it is the border between the pacific tectonic plate and other major plates. As the plates slide and move they may bump into each other or slide over or under each other. Imagine the earth’s crust broken up into several pieces. Each of these pieces is a plate (this is known as the theory of plate tectonics). The plates are floating on the earth’s surface and can change positions. When this happens it results in earthquakes and volcanoes. When one plate slides under another the intense heat and pressure can melt the rock forming magma, which then rises back to earth’s surface as lava. When plates collide it creates earthquakes, which is the jarring you may feel if you have experienced an earthquake before.
Source: USGS public domain photo