Ring of Fire
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The Ring of Fire (also known as the Pacific Ring of Fire, the Rim of Fire, the Girdle of Fire or the Circum-Pacific belt) is a tectonic belt of volcanoes and earthquakes. It is about 40,000 km (25,000 mi) long and up to about 500 km (310 mi) wide, and surrounds most of the Pacific Ocean. The Ring of Fire contains between 750 and 915 active or dormant volcanoes, around two-thirds of the world total. The exact number of volcanoes within the Ring of Fire depends on which regions are included. About 90% of the world's earthquakes, including most of its largest, occur within the belt. The Ring of Fire is not a single geological structure. It was created by the subduction of different tectonic plates at convergent boundaries around the Pacific Ocean. These include: the Antarctic, Nazca and Cocos plates subducting beneath the South American plate; the Pacific and Juan de Fuca plates beneath the North American plate; the Philippine plate beneath the Eurasian plate; and a complex boundary between the Pacific and Australian plate. The interactions at these plate boundaries have formed oceanic trenches, volcanic arcs, back-arc basins and volcanic belts. The inclusion of some areas in the Ring of Fire, such as the Antarctic Peninsula and western Indonesia, is disputed. The Ring of Fire has existed for more than 35 million years but subduction has existed for much longer in some parts of the Ring; many older extinct volcanoes are located within the Ring. More than 350 of the Ring of Fire's volcanoes have been active in historical times, while the four largest volcanic eruptions on Earth in the Holocene epoch all occurred at volcanoes in the Ring of Fire. Most of Earth's active volcanoes with summits above sea level are located in the Ring of Fire. Many of these subaerial volcanoes are stratovolcanoes (e.g. Mount St. Helens), formed by explosive eruptions of tephra alternating with effusive eruptions of lava flows. Lavas at the Ring of Fire's stratovolcanoes are mainly andesite and basaltic andesite but dacite, rhyolite, basalt and some other rarer types also occur. Other types of volcano are also found in the Ring of Fire, such as subaerial shield volcanoes (e.g. Plosky Tolbachik), and submarine seamounts (e.g. Monowai).