Ring of Fire

seismic belt
Also known as: Circum-Pacific Belt, Circum-Pacific Volcano Belt, Pacific Ring of Fire
Also called:
Circum-Pacific Belt or Pacific Ring of Fire
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Ring of Fire, long horseshoe-shaped seismically active belt of earthquake epicentres, volcanoes, and tectonic plate boundaries that fringes the Pacific basin. For much of its 40,000-km (24,900-mile) length, the belt follows chains of island arcs such as Tonga and New Hebrides, the Indonesian archipelago, the Philippines, Japan, the Kuril Islands, and the Aleutians, as well as other arc-shaped geomorphic features, such as the western coast of North America and the Andes Mountains. Volcanoes are associated with the belt throughout its length; for this reason it is called the “Ring of Fire.” A series of deep ocean troughs frame the belt on the oceanic side, and continental landmasses lie behind. Most of the world’s earthquakes, the overwhelming majority of the world’s strongest earthquakes, and approximately 75 percent of the world’s volcanoes occur within the Ring of Fire.

The Ring of Fire surrounds several tectonic plates—including the vast Pacific Plate and the smaller Philippine, Juan de Fuca, Cocos, and Nazca plates. Many of these plates are subducting under the continental plates they border. Along much of the western coast of North America, however, the Pacific Plate is sliding past the North American plate at plate intersections called transform faults.

Major volcanic events that have occurred within the Ring of Fire since 1800 included the eruptions of Mount Tambora (1815), Krakatoa (1883), Novarupta (1912), Mount Saint Helens (1980), Mount Ruiz (1985), and Mount Pinatubo (1991). The Ring of Fire has been the setting for several of the largest earthquakes in recorded history, including the Chile earthquake of 1960, the Alaska earthquake of 1964, the Chile earthquake of 2010, and the Japan earthquake of 2011 as well as the earthquake that produced the devastating Indian Ocean tsunami of 2004.

Hawaiian volcanic crater, Hawaii
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The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by John P. Rafferty.
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earthquake, any sudden shaking of the ground caused by the passage of seismic waves through Earth’s rocks. Seismic waves are produced when some form of energy stored in Earth’s crust is suddenly released, usually when masses of rock straining against one another suddenly fracture and “slip.” Earthquakes occur most often along geologic faults, narrow zones where rock masses move in relation to one another. The major fault lines of the world are located at the fringes of the huge tectonic plates that make up Earth’s crust. (See the table of major earthquakes.)

Little was understood about earthquakes until the emergence of seismology at the beginning of the 20th century. Seismology, which involves the scientific study of all aspects of earthquakes, has yielded answers to such long-standing questions as why and how earthquakes occur.

About 50,000 earthquakes large enough to be noticed without the aid of instruments occur annually over the entire Earth. Of these, approximately 100 are of sufficient size to produce substantial damage if their centres are near areas of habitation. Very great earthquakes occur on average about once per year. Over the centuries they have been responsible for millions of deaths and an incalculable amount of damage to property.

The nature of earthquakes

Causes of earthquakes

Earth’s major earthquakes occur mainly in belts coinciding with the margins of tectonic plates. This has long been apparent from early catalogs of felt earthquakes and is even more readily discernible in modern seismicity maps, which show instrumentally determined epicentres. The most important earthquake belt is the Circum-Pacific Belt, which affects many populated coastal regions around the Pacific Ocean—for example, those of New Zealand, New Guinea, Japan, the Aleutian Islands, Alaska, and the western coasts of North and South America. It is estimated that 80 percent of the energy presently released in earthquakes comes from those whose epicentres are in this belt. The seismic activity is by no means uniform throughout the belt, and there are a number of branches at various points. Because at many places the Circum-Pacific Belt is associated with volcanic activity, it has been popularly dubbed the “Pacific Ring of Fire.”

A second belt, known as the Alpide Belt, passes through the Mediterranean region eastward through Asia and joins the Circum-Pacific Belt in the East Indies. The energy released in earthquakes from this belt is about 15 percent of the world total. There also are striking connected belts of seismic activity, mainly along oceanic ridges—including those in the Arctic Ocean, the Atlantic Ocean, and the western Indian Ocean—and along the rift valleys of East Africa. This global seismicity distribution is best understood in terms of its plate tectonic setting.

Warm water fuels Hurricane Katrina. This image depicts a 3-day average of actual dea surface temperatures for the Caribbean Sea and Atlantic Ocean, from August 25-27, 2005.
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Natural forces

Earthquakes are caused by the sudden release of energy within some limited region of the rocks of the Earth. The energy can be released by elastic strain, gravity, chemical reactions, or even the motion of massive bodies. Of all these the release of elastic strain is the most important cause, because this form of energy is the only kind that can be stored in sufficient quantity in the Earth to produce major disturbances. Earthquakes associated with this type of energy release are called tectonic earthquakes.