The
Pacific Ring of Fire is an area of frequent
earthquakes and
volcanic eruptions encircling the basin of the
Pacific Ocean. In a 40,000&_160;km horseshoe shape, it is associated with a nearly continuous series of
oceanic trenches,
volcanic arcs, and
volcanic belts and/or plate movements. The Ring of Fire has 452 volcanoes and is home to over 75% of the world's active and
dormant volcanoes. It is sometimes called the
circum-Pacific belt or the
circum-Pacific seismic belt.
Ninety percent of the world's earthquakes and 80% of the world's largest earthquakes occur along the Ring of Fire. The next most seismic region (5–6% of earthquakes and 17% of the world's largest earthquakes) is the Alpide belt, which extends from Java to Sumatra through the Himalayas, the Mediterranean, and out into the Atlantic. The Mid-Atlantic Ridge is the third most prominent earthquake belt.[1][2]
The Ring of Fire is a direct result and consequence of plate tectonics and the movement and collisions of crustal plates.[3] The eastern section of the ring is the result of the Nazca Plate and the Cocos Plate being subducted beneath the westward moving South American Plate. A portion of the Pacific Plate along with the small Juan de Fuca Plate are being subducted beneath the North American Plate. Along the northern portion the northwestward moving Pacific plate is being subducted beneath the Aleutian Islands arc. Further west the Pacific plate is being subducted along the Kamchatka Peninsula arcs on south past Japan. The southern portion is more complex with a number of smaller tectonic plates in collision with the Pacific plate from the Mariana Islands, the Philippines, Bougainville, Tonga, and New Zealand. Indonesia lies between the Ring of Fire along the northeastern islands adjacent to and including New Guinea and the Alpide belt along the south and west from Sumatra, Java, Bali, Flores, and Timor. The famous and very active San Andreas Fault zone of California is a transform fault which offsets a portion of the East Pacific Rise under southwestern United States and Mexico. The motion of the fault generates numerous small earthquakes, at multiple times a day, most of which are too small to be felt.[4][5] The active Queen Charlotte Fault on the west coast of the Queen Charlotte Islands, British Columbia, Canada, has generated three large earthquakes during the 20th century a magnitude 7 event in 1929, a magnitude 8.1 occurred in 1949 (Canada's largest recorded earthquake) and a magnitude 7.4 in 1970.[6]
The December 2004 earthquake just off the coast of Sumatra was actually a part of the Alpide belt.[citation needed]
