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 August 20, 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 August 20, 2014).

Share This




More Earth & Climate News

Wednesday, August 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Green Power Blooms as Japan Unveils 'hydrangea Solar Cell'

Green Power Blooms as Japan Unveils 'hydrangea Solar Cell'

AFP (Aug. 19, 2014) A solar cell that resembles a flower is offering a new take on green energy in Japan, where one scientist is searching for renewables that look good. Duration: 01:29 Video provided by AFP
Powered by NewsLook.com
Disquieting Times for Malaysia's 'fish Listeners'

Disquieting Times for Malaysia's 'fish Listeners'

AFP (Aug. 19, 2014) Malaysia's last "fish listeners" -- practitioners of a dying local art of listening underwater to locate their quarry -- try to keep the ancient technique alive in the face of industrial trawling and the depletion of stocks. Duration: 02:29 Video provided by AFP
Powered by NewsLook.com
Wildfire Hits California's Angeles National Forest

Wildfire Hits California's Angeles National Forest

Reuters - US Online Video (Aug. 17, 2014) A wildfire sweeps across the Angeles National Forest prompting campers to quickly leave as officials began evacuating the area -- local media. Gavino Garay reports. Video provided by Reuters
Powered by NewsLook.com
Symphony Performs at Southern Utah's Red Rocks

Symphony Performs at Southern Utah's Red Rocks

AP (Aug. 16, 2014) The Utah Symphony hopes to complement the beauty of Utah's soaring red rocks and canyons with free desert performances near Utah's national parks this weekend. (Aug. 16) Video provided by AP
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