The Ring of Fire is an area of frequent seismic and volcanic activity that encircles the Pacific basin. Approximately 90% of the world’s earthquakes occur in this zone, including the largest ever recorded – Chile’s 1960 Valdivia earthquake. There are an estimated 452 volcanoes – 75% of the world’s total – located in this 40,000 km belt. On its Eastern side, the Ring of Fire stretches along South and Central America up to Canada and Alaska, and includes California’s well-known San Andreas fault zone. To the west of the Pacific, it extends from Russia down to Japan, the Philippines, Indonesia and New Zealand. The Ring of Fire finishes in Antarctica, which is home to Mount Erebus, the world’s southern-most active volcano. The volcanic eruptions and earthquakes that characterise the Ring of Fire can be explained by plate tectonics, a unifying geological theory first expounded in the 1960s. The Earth’s surface is comprised of tectonic plates that change size and shift over time. Earthquakes are caused when plates that are pushing against each other suddenly slip. Volcanoes occur only when two adjacent plates converge and one plate slides under the other, a process known as subduction. As it is pushed deeper into the Earth, the subducted plate encounters high temperatures and eventually molten rock rises to the surface and erupts.