Printer Friendly

Seismic vibes gauge Earth's crust.

New seismic observations are filling in scientists' knowledge about the thickness of Earth's crust, especially in the Southern Hemisphere.

Because vibrations traveling through any material are deflected by its irregularities, scientists can use seismic waves traveling through our planet to examine its structure. Specifically, researchers can exploit ground motions produced by large earthquakes or deliberately detonated explosions, for example, to discern the boundary between Earth's rigid crust and its softer, more viscous mantle below.

Using data collected over the past 65 years, geophysicists have estimated the crust's thickness at almost 7,500 locations, says Shane T. Detweiler of the U.S. Geological Survey in Menlo Park, Calif. More than one-third of those estimates have been produced in the past 2 years, many from data gathered by scientific expeditions in the Southern Hemisphere.

About 50 percent of Earth's crust is less than 10 kilometers thick, Detweiler and his colleagues estimate. Most thin areas are created at midocean ridges and therefore lie beneath oceans, the researchers say.

The crust on continents and their submerged fringes, continental shelves, is generally from 20 km to about 50 km thick. Only in two locales, the Himalayas of southern Asia and the central Andes of South America, is the crust thicker than 70 km, says Detweiler.--S.P.
COPYRIGHT 2005 Science Service, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2005, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:Siesmology
Author:Perkins, Sid
Publication:Science News
Article Type:Brief Article
Geographic Code:1U9CA
Date:Jan 15, 2005
Words:212
Previous Article:Palm-nut problem: Asian chewing habit linked to oral cancer.
Next Article:Big quakes can free grounded icebergs.
Topics:


Related Articles
Ocean-ridge chemistry at new heights.
The Moho is immutable no more.
Rooting for continental roots; the discovery that the old cores of continents are unusually thick is rifting traditional notions about continental...
Probing the earth's crust, deeply.
Disappointment in the deep Pacific.
Recycling the continents.
A Stirring Tale from inside Earth.
Probe could ride to Earth's core in a mass of molten iron. (Going Down?).
Icy heat: satellites look at heat flow through Antarctica's crust.
Seismic noise can yield maps of Earth's crust.

Terms of use | Privacy policy | Copyright © 2021 Farlex, Inc. | Feedback | For webmasters