Tectonica De Placas

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View of the planet Earth from the Apollo spacecraft. The Red Sea, which separates Saudi

Arabia

from the continent of Africa, is clearly visible at the top. (Photograph courtesy of NASA.)


Contents

Preface

Historical perspective

Developing the theory

"Hotspots": Mantle Some unanswered questions Plate tectonics and people
thermal plumes

Understanding platemotions

Endnotes

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This pdf-version was edited by Peter Lindeberg in December 2001. Any deviation from the

original text is non-intentional.

This book was originally published in paper form in February 1996 (design and coordination by

Martha Kiger; illustrations and production by Jane Russell). It is for sale for $7 from:

U.S. Government Printing OfficeSuperintendent of Documents, Mail Stop SSOP

Washington, DC 20402-9328

or it can be ordered directly from the U.S. Geological Survey:

Call toll-free 1-888-ASK-USGS

Or write to

USGS Information Services

Box 25286, Building 810

Denver Federal Center

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303-202-4700; Fax 303-202-4693

ISBN 0-16-048220-8

Version 1.08

The online edition contains alltext from the original book in its entirety.

Some figures have been modified to enhance legibility at screen resolutions.

Many of the images in this book are available in high resolution from the USGS Media for
Science page.

USGS Home Page
URL: http://pubs.usgs.gov/publications/text/dynamic.html

Last updated: 01.29.01

Contact: jmwatson@usgs.gov


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Inthe early 1960s, the emergence of the theory of plate tectonics started a revolution in the
earth sciences. Since then, scientists have verified and refined this theory, and now have a
much better understanding of how our planet has been shaped by plate-tectonic processes.
We now know that, directly or indirectly, plate tectonics influences nearly all geologic
processes, past and present.Indeed, the notion that the entire Earth's surface is continually
shifting has profoundly changed the way we view our world.
People benefit from, and are at the mercy of, the forces and consequences of plate tectonics.
With little or no warning, an earthquake or volcanic eruption can unleash bursts of energy far
more powerful than anything we can generate. While we have no control overplate-tectonic
processes, we now have the knowledge to learn from them. The more we know about plate
tectonics, the better we can appreciate the grandeur and beauty of the land upon which we
live, as well as the occasional violent displays of the Earth's awesome power.
This booklet gives a brief introduction to the concept of plate tectonics and complements the
visual and written information in ThisDynamic Planet (see Further reading), a map published
in 1994 by the U.S. Geological Survey (USGS) and the Smithsonian Institution. The booklet
highlights some of the people and discoveries that advanced the development of the theory
and traces its progress since its proposal. Although the general idea of plate tectonics is now
widely accepted, many aspects still continue to confound andchallenge scientists. The
earth-science revolution launched by the theory of plate tectonics is not finished.

Oldoinyo Lengai, an active volcano in the East African Rift Zone, where Africa is being pulled
apart by plate-tectonic processes. (Photograph by Jorg Keller, Albert-Ludwigs-Universität
Freiburg, Germany.)

In geologic terms, a plate is a large, rigid slab of solid rock. The word tectonicscomes from

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the Greek root "to build." Putting these two words together, we get the term plate tectonics,

which refers to how the Earth's surface is built of plates. The theory of plate tectonics states

that the Earth's outermost layer is fragmented into a dozen or more large and small plates

that are moving relative to one another as they ride atop...