MadSci Network: Earth Sciences

Re: Where are the tectonic plates connected and the ring of fire

Date: Thu Jun 25 14:34:29 1998
Posted By: David Smith, Faculty Geology, Environmental Science
Area of science: Earth Sciences
ID: 898645145.Es

The "ring of fire" specifically refers to a zone of volcanos along the shores of the Pacific Ocean, approximately 10,000 kilometers in "diameter". I put diameter in quotes because the "ring" is not even close to a circle. The map on this web site will help: volcanoes/world.html All of these volcanos are formed above subduction zones, places where one plate dives beneath another and is consumed back into the mantle. As the plate descends, it is heated and water is driven off. Adding water to hot rocks under high pressure helps to break the chemical bonds that hold the rock together and the rock may melt, rise to the surface, and erupt as a volcano. In most places it is the Pacific Plate that is being consumed, but that is not true everywhere. For example, along the coasts of North and South America, small plates (such as the Nazca plate) lie between the Pacific plate and the subduction zone and it is the small plates that are being subducted.

There is no Atlantic ring that would be comparable to the Pacific ring. The Atlantic ocean is much younger and is a growing ocean basin (whereas the Pacific is shrinking). There is, however, a string of volcanos down the middle of the Atlantic ocean. These volcanos are not at all like the ring of fire volcanos, they are formed where two plates pull apart and are generally much less explosive and less likely to build up into islands. Does this answer your question? If not, please ask additional questions of the Mad Scientist Network and I will be pleased to answer.
Dave Smith
La Salle University
Philadelphia, PA

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