Volcanic arcs and oceanic trenches partly encircling the Pacific Basin form the so-called Ring of Fire, a zone of frequent earthquakes and volcanic eruptions. The trenches are shown in blue-green. The volcanic island arcs, although not labelled, are parallel to, and always landward of, the trenches. For example, the island arc associated with the Aleutian Trench is represented by the long chain of volcanoes that make up the Aleutian Islands.
The "Ring of Fire" is an arc stretching from New Zealand, along the eastern edge of Asia, north across the Aleutian Islands of Alaska, and south along the coast of North and South America. It is composed over 75% of the world's active and dormant volcanoes.
This huge ring of volcanic and seismic (earthquake) activity was noticed and described before the invention of the plate tectonics theory. We now know that the Ring of Fire is located at the borders of the Pacific Plate and other tectonic plates.
Plates are like giant rafts of the earth's surface which often slide next to, collide with, and are forced underneath other plates. Around the Ring of Fire, the Pacific Plate is colliding with and sliding underneath other plates. This process is known as subduction and the volcanically and seismically active area nearby is known as a subduction zone. There is a tremendous amount of energy created by these plates and they easily melt rock into magma, which rises to the surface as lava and forms volcanoes.
Volcanoes are temporary features on the earth's surface and there are currently about 1500 active volcanoes in the world. About ten percent of these are located in the United States.
This is a listing of major volcanic areas in the Ring of Fire:
Click Here for prominent hot spots.
Click Here to understand plate motions.
Relief map of the tectonic plates
BBC News - January 29, 1999
Circling the Pacific Basin, on the bottom of the sea bed, lie a dramatic series of volcanic arcs and oceanic trenches. The zone - the 'Ring of Fire' - notorious for frequent earthquakes and volcanic eruptions, coincides with the edges of one of the world's main tectonic plates.
More than half of the world's active volcanoes above sea level are part of the ring.
In the past 25 years, scientists developed a theory called plate tectonics explaining the locations of volcanoes and other large-scale geologic features.
According to tectonic theory, the surface of the Earth is made up of a patchwork of massive rigid plates, about 80km thick, which float in slow motion on top of the Earth's hot, pliable interior.
The plates change size and position over time, moving at speeds of between 1cm and 10cm every year - about the speed at which fingernails grow.
New sea bed is constantly being created in the middles of the oceans - flowing out as hot lava, and rapidly cooling on contact with cold deep sea water.
To make room for the continual addition of new ocean crust, all the earth's plates move. And as they move, intense geologic activity occurs at the plate edges. < At the edges, one of three things may occur.
The plates can be moving away from each other, leaving space for new ocean floor.
Some plates are moving towards each other, causing one to submerge beneath the other.
Other boundaries slide past each other without much disturbance.
Parts of the plate boundary that slide past one another in opposite directions - such as the San Andreas Fault - cause minor earthquakes. The faults may also create cliffs or scarps thousands of feet high on the ocean bed.
But where one oceanic plate collided with and is forced deep into the Earth's interior, the subsumed plate encounters high temperatures and pressures that partially melt solid rock.
Some of this newly-formed magma rises to the Earth's surface and erupts, forming chains of violent volcanoes - like the Ring of Fire.
These narrow plate-boundary sites, known as subduction zones, are also associated with the formation of deep ocean trenches and big earthquakes.
When there is an earthquake under the sea, one side of the ocean floor suddenly drops downward, beneath the top edge of the subducting plate.
The resulting vertical fault will generate a tsunami - much as a wave machine in a swimming pool will generate one.
The movements of the plates usually allow little warning for those at risk in coastal areas.
One warning of a tsunami is that there is a rush of water away from the coastline - but this predictor may mean the forthcoming seismic wave is only minutes away.
One week before Papua New Guinea's seismic activity, a large quake was recorded to the west of Western Samoa, and another took place in Vanuatu.
The frequency of Pacific quakes and seismic activity is not coincidence.
According to the theory of continental drift, the world was made up of a single continent through most of geologic time. That continent eventually separated and drifted apart, forming into the seven continents we have today. The first comprehensive theory of continental drift was suggested by the German meteorologist Alfred Wegener in 1912. The hypothesis asserts that the continents consist of lighter rocks that rest on heavier crustal material - similar to the manner in which icebergs float on water. Wegener contended that the relative positions of the continents are not rigidly fixed but are slowly moving - at a rate of about one yard per century.
According to the generally accepted plate-tectonics theory, scientists believe that Earth's surface is broken into a number of shifting slabs or plates, which average about 50 miles in thickness. These plates move relative to one another above a hotter, deeper, more mobile zone at average rates as great as a few inches per year. Most of the world's active volcanoes are located along or near the boundaries between shifting plates and are called plate-boundary volcanoes. However, some active volcanoes are not associated with plate boundaries, and many of these so-called intra-plate volcanoes form roughly linear chains in the interior of some oceanic plates.
The Hawaiian Islands provide perhaps the best example of an intra-plate volcanic chain, developed by the northwest-moving Pacific plate passing over an inferred - hot spot - that initiates the magma-generation and volcano-formation process. The peripheral areas of the Pacific Ocean Basin, containing the boundaries of several plates, are dotted by many active volcanoes that form the so-called Ring of Fire. The Ring provides excellent examples of plate-boundary volcanoes, including Mt. St. Helens.
It was not until the 1960's that geologists gained the technology to fully understand the processes that could move the Earth's plates. They concluded that the Earth's surface was composed of not one large sheet but was composed of more than twelve major pieces of crust. Geologists call these pieces plates. These plates float across the surface of the Earth like an iceberg floats on the ocean. The driving force behind these plate movements are the convection currents in the mantle. The convection currents turn very slowly dragging the plates along with these movements. The convection currents move the plates very slowly. These plates move at only 1 to 4 inches per year!
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