Plate Tectonics: A whole new way of looking at your planet
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The Book  
Table of Contents
Introduction
In the Beginning
The Tectonic Plates
Mount St. Helen
How Plates Move
Plate Boundaries
A Changing Earth
Pangaea - All Lands
Mid-Ocean Ridges
An Ocean is Born
The Birth of an Island
Mountain Ranges
Subduction Zones
Island Arcs
The Ring of Fire
Faults
Earthquakes
Hot Spots
Mantle Plumes
Origin of Life Theories
Global Climate
Other Worlds
Welcome to Your World

Island Arcs

The journey of a plate sinking into a trench is a long and complex affair, and the effects of this journey are apparent on the face of the earth. Firstly, as the cold, stiff plate begins its arduous descent, a continuous series of earthquakes is created. The plate then starts to heat up and at a depth of about 75 miles, certain magmas are melted and rise toward the surface. Eventually these magmas make their way up into the leading edge of the overriding plate, where they add material to the crust and build volcanoes above it. If the upper plate is oceanic, the volcanoes pile up until they poke through the surface of the ocean and form an elegant arc. [Scientists believe that this arc formation has something to do with the curvature of the earth].

Examples of island arcs created in this way are the Aleutians, the Kuriles, Japan, the Ryukyus, and the Philippines, found clustered around the northern and western borders of the Pacific Plate like a necklace. There are other island arcs to the south (Indonesia and the Solomon’s), and although scientists are still puzzled by the exact origin of these southern island arcs, plate subduction is the suspected architect.
   
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