Featured Research

from universities, journals, and other organizations

U.S. Scientists, Colleagues Solve Volcanic Mystery, Learn Tears Occur In Vast Plates

Date:
January 26, 2001
Source:
University Of North Carolina At Chapel Hill
Summary:
Working on volcanoes in the remote province of Kamchatka in easternmost Russia, U.S., Russian and German geologists believe they have solved a long-standing mystery about volcanoes ringing the Pacific Ocean. The question has been why analysis of hardened lava there, also on Adak Island in Alaska's Aleutian chain and elsewhere around the globe reveals a chemical makeup different from what researchers predict it should be.

CHAPEL HILL -- Working on volcanoes in the remote province of Kamchatka in easternmost Russia, U.S., Russian and German geologists believe they have solved a long-standing mystery about volcanoes ringing the Pacific Ocean.

The question has been why analysis of hardened lava there, also on Adak Island in Alaska's Aleutian chain and elsewhere around the globe reveals a chemical makeup different from what researchers predict it should be. Pieces of the lava are named adakites because of where the primitive rocks first were discovered two decades ago.

According to the standard model of how vast pieces of the earth's surface move in relation to one another, the Pacific Plate is continuously thrusting underneath the Eurasian Plate so that North America and Asia are drawing closer. The process takes water-laced sediments on the sea floor lying atop the Pacific Plate to depths of about 60 miles deep, changing their nature through intense heat and pressure.

"That material then leaks up into the earth's upper mantle, which causes the mantle to melt, and dark basalts to come out in volcanoes as lava, the model suggests," said Dr. Jonathan M. Lees, associate professor of geology at the University of North Carolina at Chapel Hill. "What we found makes us think something different also is happening in some places."

Dr. Gene Yogodzinki of Dickinson College, a geochemist, and colleagues conducted chemical analyses indicating that pieces of the plate, or slab, also have melted, an observation contradicting the earlier belief that the slab is too cold to melt and flow to the surface as lava. Lees, a volcanologist who has been recording seismic activity on Kamchatka for the past three years, said his data suggest the current model should not be abandoned but rather changed.

A report on the work appears in the Jan. 25 issue of the journal Nature.

"There appears to be a very large tear in the slab where the Aleutians and Kamchatka intersect so that the edge of the slab is exposed to the mantle," he said. "When that happens, as it also does in some other places like California, it allows the mantle to erode the slab so that we see this very interesting and unexpected geochemical signature -- or combination of chemicals -- near some volcanoes. It's a kind of contamination, or mixing, of mantle and slab."

Scientists do not find the unusual lava in Hawaii and the Azores, which are not near the edge of any slab's subduction zone. These exemplify a different kind of volcano, one arising from what researchers call hot spots deep in the earth beneath the oceanic crust. Volcanoes formed by one slab sliding under another -- rather than just burning holes through them -- include Mt. St. Helens, Mt. Rainer, Mt. Pinatubo, Mt. Vesuvius and Mt. Fuji.

"What we've done is to explain a mysterious chemical signature in rocks with a very simple new model that has important implications for our understanding of the mantle," Lees said. "Before, the origin of adakites was the subject of much controversy because we did not have a satisfactory model for how they got ocean crust in them. Now we believe the cold slab melts because it's torn and exposed to the hot mantle."

The mantle lies about 18 miles below the continental crust and about three to five miles beneath oceanic crust. Lava comes from molten mantle rock about 60 miles beneath the surface.

Co-authors of the paper work at the Institute for Volcanic Geology and Geochemistry in Petropavlovsk-Kamchatsky in Russia and the Geochemical Institute in Goettingen, Germany.

Lees said that many geochemists and geophysicists he has discussed it with like the research because it appears to solve the mystery. Others disagree but have not been able to refute the new model.

"The more seismic and geophysical evidence we come up with in our experiments, the more we seem to find that our model is correct," he said. "For scientists like us, that's fun and pretty exciting. It's showing us how the earth works, explaining its plumbing system."


Story Source:

The above story is based on materials provided by University Of North Carolina At Chapel Hill. Note: Materials may be edited for content and length.


Cite This Page:

University Of North Carolina At Chapel Hill. "U.S. Scientists, Colleagues Solve Volcanic Mystery, Learn Tears Occur In Vast Plates." ScienceDaily. ScienceDaily, 26 January 2001. <www.sciencedaily.com/releases/2001/01/010125082537.htm>.
University Of North Carolina At Chapel Hill. (2001, January 26). U.S. Scientists, Colleagues Solve Volcanic Mystery, Learn Tears Occur In Vast Plates. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/2001/01/010125082537.htm
University Of North Carolina At Chapel Hill. "U.S. Scientists, Colleagues Solve Volcanic Mystery, Learn Tears Occur In Vast Plates." ScienceDaily. www.sciencedaily.com/releases/2001/01/010125082537.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

Europe's Highest Train Turns 80 in French Pyrenees

Europe's Highest Train Turns 80 in French Pyrenees

AFP (July 25, 2014) Europe's highest train, the little train of Artouste in the French Pyrenees, celebrates its 80th birthday. Duration: 01:05 Video provided by AFP
Powered by NewsLook.com
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

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