Featured Research

from universities, journals, and other organizations

Stress From Plate Collisions Travels Through Continents, Says University Of Michigan Geologist

Date:
August 13, 1997
Source:
University Of Michigan
Summary:
When continental plates come together to form mountain ranges, the impact from the collision bends microscopic grains in rocks more than 1,200 miles away, according to an article published in last week's issue of Science.

EDITORS: A color slide of a limestone deposit sampled in the U-M study is available on request.

ANN ARBOR---When continental plates come together to form mountain ranges, the impact from the collision bends microscopic grains in rocks more than 1,200 miles away, according to an article published in this week's issue of Science.

"Classic plate tectonics theory maintains that all activity is concentrated at the plate margins, but our evidence shows that seemingly quiet mid-continent areas are highly sensitive recorders of plate tectonic activity," said Ben A. van der Pluijm, University of Michigan professor of geological sciences.

When examined under a microscope, calcite grains in limestone samples, collected by van der Pluijm and his colleagues at more than 70 North American mid-continental locations, all showed the characteristic bending or deformation pattern produced in rocks under shearing stress. Intensities of stress recorded in the limestone samples varied directly with distance from the Appalachian and Rocky Mountain ranges.

"These grains of calcite are like stress gauges placed in the Earth long ago," said van der Pluijm. "Since each deformation pattern corresponds to a specific stress level and orientation, these patterns preserve a permanent record of the effects of plate collision and mountain-building over long periods of geologic time." Published in the Aug. 8 issue of Science, the research was conducted by van der Pluijm; John Craddock, associate professor of geology at Macalester College; U-M undergraduate student Brita Graham and U-M graduate student John H. Harris.

Stresses in continental plate interiors---a region long ignored by geologists---could provide new insights on tectonic processes, such as basin formation and fault reactivation, and offer critical input for computer modeling of plate dynamics, according to van der Pluijm.

U-M researchers collected samples from limestone deposited between 500 million and 200 million years ago---a period of time when the North American mid-continent often was covered with shallow seas. Samples were taken at regular intervals along two transects or straight lines. One sampling line extended from the Rocky Mountains in Wyoming into Minnesota. The second line, which replicated results from a previous study, originated in the Appalachian Mountain range in Tennessee and extended into Indiana.

"Surprisingly, deformation patterns from both transects were identical, even though the Appalachian range on the eastern side of the North American continent differs dramatically in age and style of mountain formation from the Cordilleran range on the western side," van der Pluijm said. "Mountain belts appear to act as 'stress filters' absorbing any variations in plate margin conditions before transmitting stress into plate interiors."

While the orientation of the calcite grain stress indicators did not change along either transect, the level of stress recorded decreased steadily with distance from the mountain range. Stress levels recorded in Wyoming nearest the Rockies, for example, were about five times greater than those recorded in western Minnesota.

"Our data show that mid-continent areas are not quiet and tectonically dead, as geologists believed," van der Pluijm said. "Transmitted stresses were associated with a host of geologic phenomena, including motion and earthquakes along ancient faults created long before recent mountain-building occurred."

The research project was funded by the Pew Charitable Trust, the Blandin Foundation, the Huron Mountain Wildlife Foundation and the National Science Foundation. U-M senior Brita Graham participated in the project through the U-M College of Literature, Science, and the Arts' Undergraduate Research Opportunity Program, which facilitates undergraduate involvement in faculty research.


Story Source:

The above story is based on materials provided by University Of Michigan. Note: Materials may be edited for content and length.


Cite This Page:

University Of Michigan. "Stress From Plate Collisions Travels Through Continents, Says University Of Michigan Geologist." ScienceDaily. ScienceDaily, 13 August 1997. <www.sciencedaily.com/releases/1997/08/970813063905.htm>.
University Of Michigan. (1997, August 13). Stress From Plate Collisions Travels Through Continents, Says University Of Michigan Geologist. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/1997/08/970813063905.htm
University Of Michigan. "Stress From Plate Collisions Travels Through Continents, Says University Of Michigan Geologist." ScienceDaily. www.sciencedaily.com/releases/1997/08/970813063905.htm (accessed July 25, 2014).

Share This




More Earth & Climate News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Goma Cheese Brings Whiff of New Hope to DRC

Goma Cheese Brings Whiff of New Hope to DRC

Reuters - Business Video Online (July 24, 2014) The eastern region of the Democratic Republic of Congo, mainly known for conflict and instability, is an unlikely place for the production of fine cheese. But a farm in the village of Masisi, in North Kivu is slowly transforming perceptions of the area. Known simply as Goma cheese, the Congolese version of Dutch gouda has gained popularity through out the region. Ciara Sutton reports. Video provided by Reuters
Powered by NewsLook.com
Bill Gates: Health, Agriculture Key to Africa's Development

Bill Gates: Health, Agriculture Key to Africa's Development

AFP (July 24, 2014) Health and agriculture development are key if African countries are to overcome poverty and grow, US software billionaire Bill Gates said Thursday, as he received an honourary degree in Ethiopia. Duration: 00:36 Video provided by AFP
Powered by NewsLook.com
Higgins Breaks Record at Mt. Washington

Higgins Breaks Record at Mt. Washington

Driving Sports (July 24, 2014) Subaru Rally Team USA drivers David Higgins and Travis Pastrana face off against a global contingent of racers at the annual Mt. Washington Hillclimb in New Hampshire. Includes exclusive in-car footage from Higgins' record attempt. Video provided by Driving Sports
Powered by NewsLook.com
Storm Kills Three, Injures 20 at Virginia Campground

Storm Kills Three, Injures 20 at Virginia Campground

Reuters - US Online Video (July 24, 2014) A likely tornado tears through an eastern Virginia campground, killing three and injuring at least 20. Linda So reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

    Health News

      Environment News

        Technology News



          Save/Print:
          Share:

          Free Subscriptions


          Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

          Get Social & Mobile


          Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

          Have Feedback?


          Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
          Mobile: iPhone Android Web
          Follow: Facebook Twitter Google+
          Subscribe: RSS Feeds Email Newsletters
          Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins